Use tomllib on Python 3.11 (#2903)

[etc/vim.git] / tests / test_black.py

diff --git a/tests/test_black.py b/tests/test_black.py
index 3ed5daa4b494afb5b8a0918d8f60e7426f623201..b1bf1772550588d32fc6d5a8c2a630628542f1ad 100644 (file)
--- a/tests/test_black.py
+++ b/tests/test_black.py
@@ -1,80 +1,77 @@
 #!/usr/bin/env python3
 #!/usr/bin/env python3

+

 import asyncio
 import asyncio

+import inspect
+import io

 import logging
 import logging

-from concurrent.futures import ThreadPoolExecutor
-from contextlib import contextmanager
-from functools import partial
-from io import BytesIO, TextIOWrapper
+import multiprocessing

 import os
 import os

-from pathlib import Path
-import regex as re

 import sys
 import sys

-from tempfile import TemporaryDirectory
-from typing import Any, BinaryIO, Dict, Generator, List, Tuple, Iterator, TypeVar
+import types

 import unittest
 import unittest

-from unittest.mock import patch, MagicMock
+from concurrent.futures import ThreadPoolExecutor
+from contextlib import contextmanager, redirect_stderr
+from dataclasses import replace
+from io import BytesIO
+from pathlib import Path
+from platform import system
+from tempfile import TemporaryDirectory
+from typing import (
+    Any,
+    Callable,
+    Dict,
+    Iterator,
+    List,
+    Optional,
+    Sequence,
+    TypeVar,
+    Union,
+)
+from unittest.mock import MagicMock, patch

 
 import click
 
 import click

+import pytest
+import re

 from click import unstyle
 from click.testing import CliRunner
 from click import unstyle
 from click.testing import CliRunner

+from pathspec import PathSpec

 
 import black
 
 import black

+import black.files

 from black import Feature, TargetVersion
 from black import Feature, TargetVersion

-
-try:
-    import blackd
-    from aiohttp.test_utils import AioHTTPTestCase, unittest_run_loop
-    from aiohttp import web
-except ImportError:
-    has_blackd_deps = False
-else:
-    has_blackd_deps = True
-
-from pathspec import PathSpec
+from black import re_compile_maybe_verbose as compile_pattern
+from black.cache import get_cache_dir, get_cache_file
+from black.debug import DebugVisitor
+from black.output import color_diff, diff
+from black.report import Report

 
 # Import other test classes
 
 # Import other test classes

-from .test_primer import PrimerCLITests  # noqa: F401
+from tests.util import (
+    DATA_DIR,
+    DEFAULT_MODE,
+    DETERMINISTIC_HEADER,
+    PROJECT_ROOT,
+    PY36_VERSIONS,
+    THIS_DIR,
+    BlackBaseTestCase,
+    assert_format,
+    change_directory,
+    dump_to_stderr,
+    ff,
+    fs,
+    read_data,
+)

 
 

-
-ff = partial(black.format_file_in_place, mode=black.FileMode(), fast=True)
-fs = partial(black.format_str, mode=black.FileMode())

 THIS_FILE = Path(__file__)
 THIS_FILE = Path(__file__)

-THIS_DIR = THIS_FILE.parent
-PROJECT_ROOT = THIS_DIR.parent
-DETERMINISTIC_HEADER = "[Deterministic header]"
-EMPTY_LINE = "# EMPTY LINE WITH WHITESPACE" + " (this comment will be removed)"
-PY36_ARGS = [
-    f"--target-version={version.name.lower()}" for version in black.PY36_VERSIONS
-]
+EMPTY_CONFIG = THIS_DIR / "data" / "empty_pyproject.toml"
+PY36_ARGS = [f"--target-version={version.name.lower()}" for version in PY36_VERSIONS]
+DEFAULT_EXCLUDE = black.re_compile_maybe_verbose(black.const.DEFAULT_EXCLUDES)
+DEFAULT_INCLUDE = black.re_compile_maybe_verbose(black.const.DEFAULT_INCLUDES)

 T = TypeVar("T")
 R = TypeVar("R")
 
 T = TypeVar("T")
 R = TypeVar("R")
 

-
-def dump_to_stderr(*output: str) -> str:
-    return "\n" + "\n".join(output) + "\n"
-
-
-def read_data(name: str, data: bool = True) -> Tuple[str, str]:
-    """read_data('test_name') -> 'input', 'output'"""
-    if not name.endswith((".py", ".pyi", ".out", ".diff")):
-        name += ".py"
-    _input: List[str] = []
-    _output: List[str] = []
-    base_dir = THIS_DIR / "data" if data else PROJECT_ROOT
-    with open(base_dir / name, "r", encoding="utf8") as test:
-        lines = test.readlines()
-    result = _input
-    for line in lines:
-        line = line.replace(EMPTY_LINE, "")
-        if line.rstrip() == "# output":
-            result = _output
-            continue
-
-        result.append(line)
-    if _input and not _output:
-        # If there's no output marker, treat the entire file as already pre-formatted.
-        _output = _input[:]
-    return "".join(_input).strip() + "\n", "".join(_output).strip() + "\n"
+# Match the time output in a diff, but nothing else
+DIFF_TIME = re.compile(r"\t[\d\-:+\. ]+")

 
 
 @contextmanager
 
 
 @contextmanager


@@ -83,7 +80,7 @@ def cache_dir(exists: bool = True) -> Iterator[Path]:
         cache_dir = Path(workspace)
         if not exists:
             cache_dir = cache_dir / "new"
         cache_dir = Path(workspace)
         if not exists:
             cache_dir = cache_dir / "new"

-        with patch("black.CACHE_DIR", cache_dir):
+        with patch("black.cache.CACHE_DIR", cache_dir):

             yield cache_dir
 
 
             yield cache_dir
 
 


@@ -99,99 +96,49 @@ def event_loop() -> Iterator[None]:
         loop.close()
 
 
         loop.close()
 
 

-@contextmanager
-def skip_if_exception(e: str) -> Iterator[None]:
-    try:
-        yield
-    except Exception as exc:
-        if exc.__class__.__name__ == e:
-            unittest.skip(f"Encountered expected exception {exc}, skipping")
-        else:
-            raise
+class FakeContext(click.Context):
+    """A fake click Context for when calling functions that need it."""

 
 

+    def __init__(self) -> None:
+        self.default_map: Dict[str, Any] = {}
+        # Dummy root, since most of the tests don't care about it
+        self.obj: Dict[str, Any] = {"root": PROJECT_ROOT}

 
 

-class BlackRunner(CliRunner):
-    """Modify CliRunner so that stderr is not merged with stdout.

 
 

-    This is a hack that can be removed once we depend on Click 7.x"""
+class FakeParameter(click.Parameter):
+    """A fake click Parameter for when calling functions that need it."""

 
     def __init__(self) -> None:
 
     def __init__(self) -> None:

-        self.stderrbuf = BytesIO()
-        self.stdoutbuf = BytesIO()
-        self.stdout_bytes = b""
-        self.stderr_bytes = b""
-        super().__init__()
-
-    @contextmanager
-    def isolation(self, *args: Any, **kwargs: Any) -> Generator[BinaryIO, None, None]:
-        with super().isolation(*args, **kwargs) as output:
-            try:
-                hold_stderr = sys.stderr
-                sys.stderr = TextIOWrapper(self.stderrbuf, encoding=self.charset)
-                yield output
-            finally:
-                self.stdout_bytes = sys.stdout.buffer.getvalue()  # type: ignore
-                self.stderr_bytes = sys.stderr.buffer.getvalue()  # type: ignore
-                sys.stderr = hold_stderr
-
-
-class BlackTestCase(unittest.TestCase):
-    maxDiff = None
-
-    def assertFormatEqual(self, expected: str, actual: str) -> None:
-        if actual != expected and not os.environ.get("SKIP_AST_PRINT"):
-            bdv: black.DebugVisitor[Any]
-            black.out("Expected tree:", fg="green")
-            try:
-                exp_node = black.lib2to3_parse(expected)
-                bdv = black.DebugVisitor()
-                list(bdv.visit(exp_node))
-            except Exception as ve:
-                black.err(str(ve))
-            black.out("Actual tree:", fg="red")
-            try:
-                exp_node = black.lib2to3_parse(actual)
-                bdv = black.DebugVisitor()
-                list(bdv.visit(exp_node))
-            except Exception as ve:
-                black.err(str(ve))
-        self.assertEqual(expected, actual)
+        pass

 
 

-    def invokeBlack(
-        self, args: List[str], exit_code: int = 0, ignore_config: bool = True
-    ) -> None:
-        runner = BlackRunner()
-        if ignore_config:
-            args = ["--verbose", "--config", str(THIS_DIR / "empty.toml"), *args]
-        result = runner.invoke(black.main, args)
-        self.assertEqual(
-            result.exit_code,
-            exit_code,
-            msg=(
-                f"Failed with args: {args}\n"
-                f"stdout: {runner.stdout_bytes.decode()!r}\n"
-                f"stderr: {runner.stderr_bytes.decode()!r}\n"
-                f"exception: {result.exception}"
-            ),
-        )

 
 

-    @patch("black.dump_to_file", dump_to_stderr)
-    def checkSourceFile(self, name: str) -> None:
-        path = THIS_DIR.parent / name
-        source, expected = read_data(str(path), data=False)
-        actual = fs(source)
-        self.assertFormatEqual(expected, actual)
-        black.assert_equivalent(source, actual)
-        black.assert_stable(source, actual, black.FileMode())
-        self.assertFalse(ff(path))
+class BlackRunner(CliRunner):
+    """Make sure STDOUT and STDERR are kept separate when testing Black via its CLI."""

 
 

-    @patch("black.dump_to_file", dump_to_stderr)
-    def test_empty(self) -> None:
-        source = expected = ""
-        actual = fs(source)
-        self.assertFormatEqual(expected, actual)
-        black.assert_equivalent(source, actual)
-        black.assert_stable(source, actual, black.FileMode())
+    def __init__(self) -> None:
+        super().__init__(mix_stderr=False)
+
+
+def invokeBlack(
+    args: List[str], exit_code: int = 0, ignore_config: bool = True
+) -> None:
+    runner = BlackRunner()
+    if ignore_config:
+        args = ["--verbose", "--config", str(THIS_DIR / "empty.toml"), *args]
+    result = runner.invoke(black.main, args, catch_exceptions=False)
+    assert result.stdout_bytes is not None
+    assert result.stderr_bytes is not None
+    msg = (
+        f"Failed with args: {args}\n"
+        f"stdout: {result.stdout_bytes.decode()!r}\n"
+        f"stderr: {result.stderr_bytes.decode()!r}\n"
+        f"exception: {result.exception}"
+    )
+    assert result.exit_code == exit_code, msg
+
+
+class BlackTestCase(BlackBaseTestCase):
+    invokeBlack = staticmethod(invokeBlack)

 
     def test_empty_ff(self) -> None:
         expected = ""
 
     def test_empty_ff(self) -> None:
         expected = ""


@@ -204,56 +151,28 @@ class BlackTestCase(unittest.TestCase):
             os.unlink(tmp_file)
         self.assertFormatEqual(expected, actual)
 
             os.unlink(tmp_file)
         self.assertFormatEqual(expected, actual)
 

-    def test_self(self) -> None:
-        self.checkSourceFile("tests/test_black.py")
-
-    def test_black(self) -> None:
-        self.checkSourceFile("src/black/__init__.py")
-
-    def test_pygram(self) -> None:
-        self.checkSourceFile("src/blib2to3/pygram.py")
-
-    def test_pytree(self) -> None:
-        self.checkSourceFile("src/blib2to3/pytree.py")
-
-    def test_conv(self) -> None:
-        self.checkSourceFile("src/blib2to3/pgen2/conv.py")
-
-    def test_driver(self) -> None:
-        self.checkSourceFile("src/blib2to3/pgen2/driver.py")
-
-    def test_grammar(self) -> None:
-        self.checkSourceFile("src/blib2to3/pgen2/grammar.py")
-
-    def test_literals(self) -> None:
-        self.checkSourceFile("src/blib2to3/pgen2/literals.py")
-
-    def test_parse(self) -> None:
-        self.checkSourceFile("src/blib2to3/pgen2/parse.py")
-
-    def test_pgen(self) -> None:
-        self.checkSourceFile("src/blib2to3/pgen2/pgen.py")
-
-    def test_tokenize(self) -> None:
-        self.checkSourceFile("src/blib2to3/pgen2/tokenize.py")
-
-    def test_token(self) -> None:
-        self.checkSourceFile("src/blib2to3/pgen2/token.py")
-
-    def test_setup(self) -> None:
-        self.checkSourceFile("setup.py")
+    def test_experimental_string_processing_warns(self) -> None:
+        self.assertWarns(
+            black.mode.Deprecated, black.Mode, experimental_string_processing=True
+        )

 
     def test_piping(self) -> None:
         source, expected = read_data("src/black/__init__", data=False)
         result = BlackRunner().invoke(
             black.main,
 
     def test_piping(self) -> None:
         source, expected = read_data("src/black/__init__", data=False)
         result = BlackRunner().invoke(
             black.main,

-            ["-", "--fast", f"--line-length={black.DEFAULT_LINE_LENGTH}"],
+            [
+                "-",
+                "--fast",
+                f"--line-length={black.DEFAULT_LINE_LENGTH}",
+                f"--config={EMPTY_CONFIG}",
+            ],

             input=BytesIO(source.encode("utf8")),
         )
         self.assertEqual(result.exit_code, 0)
         self.assertFormatEqual(expected, result.output)
             input=BytesIO(source.encode("utf8")),
         )
         self.assertEqual(result.exit_code, 0)
         self.assertFormatEqual(expected, result.output)

-        black.assert_equivalent(source, result.output)
-        black.assert_stable(source, result.output, black.FileMode())
+        if source != result.output:
+            black.assert_equivalent(source, result.output)
+            black.assert_stable(source, result.output, DEFAULT_MODE)

 
     def test_piping_diff(self) -> None:
         diff_header = re.compile(
 
     def test_piping_diff(self) -> None:
         diff_header = re.compile(


@@ -262,13 +181,12 @@ class BlackTestCase(unittest.TestCase):
         )
         source, _ = read_data("expression.py")
         expected, _ = read_data("expression.diff")
         )
         source, _ = read_data("expression.py")
         expected, _ = read_data("expression.diff")

-        config = THIS_DIR / "data" / "empty_pyproject.toml"

         args = [
             "-",
             "--fast",
             f"--line-length={black.DEFAULT_LINE_LENGTH}",
             "--diff",
         args = [
             "-",
             "--fast",
             f"--line-length={black.DEFAULT_LINE_LENGTH}",
             "--diff",

-            f"--config={config}",
+            f"--config={EMPTY_CONFIG}",

         ]
         result = BlackRunner().invoke(
             black.main, args, input=BytesIO(source.encode("utf8"))
         ]
         result = BlackRunner().invoke(
             black.main, args, input=BytesIO(source.encode("utf8"))


@@ -280,67 +198,40 @@ class BlackTestCase(unittest.TestCase):
 
     def test_piping_diff_with_color(self) -> None:
         source, _ = read_data("expression.py")
 
     def test_piping_diff_with_color(self) -> None:
         source, _ = read_data("expression.py")

-        config = THIS_DIR / "data" / "empty_pyproject.toml"

         args = [
             "-",
             "--fast",
             f"--line-length={black.DEFAULT_LINE_LENGTH}",
             "--diff",
             "--color",
         args = [
             "-",
             "--fast",
             f"--line-length={black.DEFAULT_LINE_LENGTH}",
             "--diff",
             "--color",

-            f"--config={config}",
+            f"--config={EMPTY_CONFIG}",

         ]
         result = BlackRunner().invoke(
             black.main, args, input=BytesIO(source.encode("utf8"))
         )
         actual = result.output
         # Again, the contents are checked in a different test, so only look for colors.
         ]
         result = BlackRunner().invoke(
             black.main, args, input=BytesIO(source.encode("utf8"))
         )
         actual = result.output
         # Again, the contents are checked in a different test, so only look for colors.

-        self.assertIn("\033[1;37m", actual)
+        self.assertIn("\033[1m", actual)

         self.assertIn("\033[36m", actual)
         self.assertIn("\033[32m", actual)
         self.assertIn("\033[31m", actual)
         self.assertIn("\033[0m", actual)
 
     @patch("black.dump_to_file", dump_to_stderr)
         self.assertIn("\033[36m", actual)
         self.assertIn("\033[32m", actual)
         self.assertIn("\033[31m", actual)
         self.assertIn("\033[0m", actual)
 
     @patch("black.dump_to_file", dump_to_stderr)

-    def test_function(self) -> None:
-        source, expected = read_data("function")
-        actual = fs(source)
-        self.assertFormatEqual(expected, actual)
-        black.assert_equivalent(source, actual)
-        black.assert_stable(source, actual, black.FileMode())
-
-    @patch("black.dump_to_file", dump_to_stderr)
-    def test_function2(self) -> None:
-        source, expected = read_data("function2")
-        actual = fs(source)
-        self.assertFormatEqual(expected, actual)
-        black.assert_equivalent(source, actual)
-        black.assert_stable(source, actual, black.FileMode())
-
-    @patch("black.dump_to_file", dump_to_stderr)
-    def test_function_trailing_comma(self) -> None:
-        source, expected = read_data("function_trailing_comma")
-        actual = fs(source)
-        self.assertFormatEqual(expected, actual)
-        black.assert_equivalent(source, actual)
-        black.assert_stable(source, actual, black.FileMode())
-
-    @patch("black.dump_to_file", dump_to_stderr)
-    def test_expression(self) -> None:
-        source, expected = read_data("expression")
-        actual = fs(source)
+    def _test_wip(self) -> None:
+        source, expected = read_data("wip")
+        sys.settrace(tracefunc)
+        mode = replace(
+            DEFAULT_MODE,
+            experimental_string_processing=False,
+            target_versions={black.TargetVersion.PY38},
+        )
+        actual = fs(source, mode=mode)
+        sys.settrace(None)

         self.assertFormatEqual(expected, actual)
         black.assert_equivalent(source, actual)
         black.assert_stable(source, actual, black.FileMode())
 
         self.assertFormatEqual(expected, actual)
         black.assert_equivalent(source, actual)
         black.assert_stable(source, actual, black.FileMode())
 

-    @patch("black.dump_to_file", dump_to_stderr)
-    def test_pep_572(self) -> None:
-        source, expected = read_data("pep_572")
-        actual = fs(source)
-        self.assertFormatEqual(expected, actual)
-        black.assert_stable(source, actual, black.FileMode())
-        if sys.version_info >= (3, 8):
-            black.assert_equivalent(source, actual)
-

     def test_pep_572_version_detection(self) -> None:
         source, _ = read_data("pep_572")
         root = black.lib2to3_parse(source)
     def test_pep_572_version_detection(self) -> None:
         source, _ = read_data("pep_572")
         root = black.lib2to3_parse(source)


@@ -361,7 +252,7 @@ class BlackTestCase(unittest.TestCase):
         self.assertFormatEqual(expected, actual)
         with patch("black.dump_to_file", dump_to_stderr):
             black.assert_equivalent(source, actual)
         self.assertFormatEqual(expected, actual)
         with patch("black.dump_to_file", dump_to_stderr):
             black.assert_equivalent(source, actual)

-            black.assert_stable(source, actual, black.FileMode())
+            black.assert_stable(source, actual, DEFAULT_MODE)

 
     def test_expression_diff(self) -> None:
         source, _ = read_data("expression.py")
 
     def test_expression_diff(self) -> None:
         source, _ = read_data("expression.py")


@@ -372,13 +263,14 @@ class BlackTestCase(unittest.TestCase):
             r"\d\d:\d\d:\d\d\.\d\d\d\d\d\d \+\d\d\d\d"
         )
         try:
             r"\d\d:\d\d:\d\d\.\d\d\d\d\d\d \+\d\d\d\d"
         )
         try:

-            result = BlackRunner().invoke(black.main, ["--diff", str(tmp_file)])
+            result = BlackRunner().invoke(
+                black.main, ["--diff", str(tmp_file), f"--config={EMPTY_CONFIG}"]
+            )

             self.assertEqual(result.exit_code, 0)
         finally:
             os.unlink(tmp_file)
         actual = result.output
         actual = diff_header.sub(DETERMINISTIC_HEADER, actual)
             self.assertEqual(result.exit_code, 0)
         finally:
             os.unlink(tmp_file)
         actual = result.output
         actual = diff_header.sub(DETERMINISTIC_HEADER, actual)

-        actual = actual.rstrip() + "\n"  # the diff output has a trailing space

         if expected != actual:
             dump = black.dump_to_file(actual)
             msg = (
         if expected != actual:
             dump = black.dump_to_file(actual)
             msg = (


@@ -394,36 +286,20 @@ class BlackTestCase(unittest.TestCase):
         tmp_file = Path(black.dump_to_file(source))
         try:
             result = BlackRunner().invoke(
         tmp_file = Path(black.dump_to_file(source))
         try:
             result = BlackRunner().invoke(

-                black.main, ["--diff", "--color", str(tmp_file)]
+                black.main,
+                ["--diff", "--color", str(tmp_file), f"--config={EMPTY_CONFIG}"],

             )
         finally:
             os.unlink(tmp_file)
         actual = result.output
         # We check the contents of the diff in `test_expression_diff`. All
         # we need to check here is that color codes exist in the result.
             )
         finally:
             os.unlink(tmp_file)
         actual = result.output
         # We check the contents of the diff in `test_expression_diff`. All
         # we need to check here is that color codes exist in the result.

-        self.assertIn("\033[1;37m", actual)
+        self.assertIn("\033[1m", actual)

         self.assertIn("\033[36m", actual)
         self.assertIn("\033[32m", actual)
         self.assertIn("\033[31m", actual)
         self.assertIn("\033[0m", actual)
 
         self.assertIn("\033[36m", actual)
         self.assertIn("\033[32m", actual)
         self.assertIn("\033[31m", actual)
         self.assertIn("\033[0m", actual)
 

-    @patch("black.dump_to_file", dump_to_stderr)
-    def test_fstring(self) -> None:
-        source, expected = read_data("fstring")
-        actual = fs(source)
-        self.assertFormatEqual(expected, actual)
-        black.assert_equivalent(source, actual)
-        black.assert_stable(source, actual, black.FileMode())
-
-    @patch("black.dump_to_file", dump_to_stderr)
-    def test_pep_570(self) -> None:
-        source, expected = read_data("pep_570")
-        actual = fs(source)
-        self.assertFormatEqual(expected, actual)
-        black.assert_stable(source, actual, black.FileMode())
-        if sys.version_info >= (3, 8):
-            black.assert_equivalent(source, actual)
-

     def test_detect_pos_only_arguments(self) -> None:
         source, _ = read_data("pep_570")
         root = black.lib2to3_parse(source)
     def test_detect_pos_only_arguments(self) -> None:
         source, _ = read_data("pep_570")
         root = black.lib2to3_parse(source)


@@ -435,374 +311,105 @@ class BlackTestCase(unittest.TestCase):
     @patch("black.dump_to_file", dump_to_stderr)
     def test_string_quotes(self) -> None:
         source, expected = read_data("string_quotes")
     @patch("black.dump_to_file", dump_to_stderr)
     def test_string_quotes(self) -> None:
         source, expected = read_data("string_quotes")

-        actual = fs(source)
-        self.assertFormatEqual(expected, actual)
-        black.assert_equivalent(source, actual)
-        black.assert_stable(source, actual, black.FileMode())
-        mode = black.FileMode(string_normalization=False)
+        mode = black.Mode(preview=True)
+        assert_format(source, expected, mode)
+        mode = replace(mode, string_normalization=False)

         not_normalized = fs(source, mode=mode)
         self.assertFormatEqual(source.replace("\\\n", ""), not_normalized)
         black.assert_equivalent(source, not_normalized)
         black.assert_stable(source, not_normalized, mode=mode)
 
         not_normalized = fs(source, mode=mode)
         self.assertFormatEqual(source.replace("\\\n", ""), not_normalized)
         black.assert_equivalent(source, not_normalized)
         black.assert_stable(source, not_normalized, mode=mode)
 

-    @patch("black.dump_to_file", dump_to_stderr)
-    def test_docstring(self) -> None:
-        source, expected = read_data("docstring")
-        actual = fs(source)
-        self.assertFormatEqual(expected, actual)
-        black.assert_equivalent(source, actual)
-        black.assert_stable(source, actual, black.FileMode())
-
-    def test_long_strings(self) -> None:
-        """Tests for splitting long strings."""
-        source, expected = read_data("long_strings")
-        actual = fs(source)
-        self.assertFormatEqual(expected, actual)
-        black.assert_equivalent(source, actual)
-        black.assert_stable(source, actual, black.FileMode())
-
-    @patch("black.dump_to_file", dump_to_stderr)
-    def test_long_strings__edge_case(self) -> None:
-        """Edge-case tests for splitting long strings."""
-        source, expected = read_data("long_strings__edge_case")
-        actual = fs(source)
-        self.assertFormatEqual(expected, actual)
-        black.assert_equivalent(source, actual)
-        black.assert_stable(source, actual, black.FileMode())
-
-    @patch("black.dump_to_file", dump_to_stderr)
-    def test_long_strings__regression(self) -> None:
-        """Regression tests for splitting long strings."""
-        source, expected = read_data("long_strings__regression")
-        actual = fs(source)
-        self.assertFormatEqual(expected, actual)
-        black.assert_equivalent(source, actual)
-        black.assert_stable(source, actual, black.FileMode())
-
-    @patch("black.dump_to_file", dump_to_stderr)
-    def test_slices(self) -> None:
-        source, expected = read_data("slices")
-        actual = fs(source)
-        self.assertFormatEqual(expected, actual)
-        black.assert_equivalent(source, actual)
-        black.assert_stable(source, actual, black.FileMode())
-
-    @patch("black.dump_to_file", dump_to_stderr)
-    def test_comments(self) -> None:
-        source, expected = read_data("comments")
-        actual = fs(source)
-        self.assertFormatEqual(expected, actual)
-        black.assert_equivalent(source, actual)
-        black.assert_stable(source, actual, black.FileMode())
-
-    @patch("black.dump_to_file", dump_to_stderr)
-    def test_comments2(self) -> None:
-        source, expected = read_data("comments2")
-        actual = fs(source)
-        self.assertFormatEqual(expected, actual)
-        black.assert_equivalent(source, actual)
-        black.assert_stable(source, actual, black.FileMode())
-
-    @patch("black.dump_to_file", dump_to_stderr)
-    def test_comments3(self) -> None:
-        source, expected = read_data("comments3")
-        actual = fs(source)
-        self.assertFormatEqual(expected, actual)
-        black.assert_equivalent(source, actual)
-        black.assert_stable(source, actual, black.FileMode())
+    def test_skip_magic_trailing_comma(self) -> None:
+        source, _ = read_data("expression.py")
+        expected, _ = read_data("expression_skip_magic_trailing_comma.diff")
+        tmp_file = Path(black.dump_to_file(source))
+        diff_header = re.compile(
+            rf"{re.escape(str(tmp_file))}\t\d\d\d\d-\d\d-\d\d "
+            r"\d\d:\d\d:\d\d\.\d\d\d\d\d\d \+\d\d\d\d"
+        )
+        try:
+            result = BlackRunner().invoke(
+                black.main, ["-C", "--diff", str(tmp_file), f"--config={EMPTY_CONFIG}"]
+            )
+            self.assertEqual(result.exit_code, 0)
+        finally:
+            os.unlink(tmp_file)
+        actual = result.output
+        actual = diff_header.sub(DETERMINISTIC_HEADER, actual)
+        actual = actual.rstrip() + "\n"  # the diff output has a trailing space
+        if expected != actual:
+            dump = black.dump_to_file(actual)
+            msg = (
+                "Expected diff isn't equal to the actual. If you made changes to"
+                " expression.py and this is an anticipated difference, overwrite"
+                f" tests/data/expression_skip_magic_trailing_comma.diff with {dump}"
+            )
+            self.assertEqual(expected, actual, msg)

 
     @patch("black.dump_to_file", dump_to_stderr)
 
     @patch("black.dump_to_file", dump_to_stderr)

-    def test_comments4(self) -> None:
-        source, expected = read_data("comments4")
+    def test_async_as_identifier(self) -> None:
+        source_path = (THIS_DIR / "data" / "async_as_identifier.py").resolve()
+        source, expected = read_data("async_as_identifier")

         actual = fs(source)
         self.assertFormatEqual(expected, actual)
         actual = fs(source)
         self.assertFormatEqual(expected, actual)

-        black.assert_equivalent(source, actual)
-        black.assert_stable(source, actual, black.FileMode())
+        major, minor = sys.version_info[:2]
+        if major < 3 or (major <= 3 and minor < 7):
+            black.assert_equivalent(source, actual)
+        black.assert_stable(source, actual, DEFAULT_MODE)
+        # ensure black can parse this when the target is 3.6
+        self.invokeBlack([str(source_path), "--target-version", "py36"])
+        # but not on 3.7, because async/await is no longer an identifier
+        self.invokeBlack([str(source_path), "--target-version", "py37"], exit_code=123)

 
     @patch("black.dump_to_file", dump_to_stderr)
 
     @patch("black.dump_to_file", dump_to_stderr)

-    def test_comments5(self) -> None:
-        source, expected = read_data("comments5")
+    def test_python37(self) -> None:
+        source_path = (THIS_DIR / "data" / "python37.py").resolve()
+        source, expected = read_data("python37")

         actual = fs(source)
         self.assertFormatEqual(expected, actual)
         actual = fs(source)
         self.assertFormatEqual(expected, actual)

-        black.assert_equivalent(source, actual)
-        black.assert_stable(source, actual, black.FileMode())
+        major, minor = sys.version_info[:2]
+        if major > 3 or (major == 3 and minor >= 7):
+            black.assert_equivalent(source, actual)
+        black.assert_stable(source, actual, DEFAULT_MODE)
+        # ensure black can parse this when the target is 3.7
+        self.invokeBlack([str(source_path), "--target-version", "py37"])
+        # but not on 3.6, because we use async as a reserved keyword
+        self.invokeBlack([str(source_path), "--target-version", "py36"], exit_code=123)

 
 

-    @patch("black.dump_to_file", dump_to_stderr)
-    def test_comments6(self) -> None:
-        source, expected = read_data("comments6")
-        actual = fs(source)
-        self.assertFormatEqual(expected, actual)
-        black.assert_equivalent(source, actual)
-        black.assert_stable(source, actual, black.FileMode())
+    def test_tab_comment_indentation(self) -> None:
+        contents_tab = "if 1:\n\tif 2:\n\t\tpass\n\t# comment\n\tpass\n"
+        contents_spc = "if 1:\n    if 2:\n        pass\n    # comment\n    pass\n"
+        self.assertFormatEqual(contents_spc, fs(contents_spc))
+        self.assertFormatEqual(contents_spc, fs(contents_tab))

 
 

-    @patch("black.dump_to_file", dump_to_stderr)
-    def test_comments7(self) -> None:
-        source, expected = read_data("comments7")
-        actual = fs(source)
-        self.assertFormatEqual(expected, actual)
-        black.assert_equivalent(source, actual)
-        black.assert_stable(source, actual, black.FileMode())
+        contents_tab = "if 1:\n\tif 2:\n\t\tpass\n\t\t# comment\n\tpass\n"
+        contents_spc = "if 1:\n    if 2:\n        pass\n        # comment\n    pass\n"
+        self.assertFormatEqual(contents_spc, fs(contents_spc))
+        self.assertFormatEqual(contents_spc, fs(contents_tab))

 
 

-    @patch("black.dump_to_file", dump_to_stderr)
-    def test_comment_after_escaped_newline(self) -> None:
-        source, expected = read_data("comment_after_escaped_newline")
-        actual = fs(source)
-        self.assertFormatEqual(expected, actual)
-        black.assert_equivalent(source, actual)
-        black.assert_stable(source, actual, black.FileMode())
+        # mixed tabs and spaces (valid Python 2 code)
+        contents_tab = "if 1:\n        if 2:\n\t\tpass\n\t# comment\n        pass\n"
+        contents_spc = "if 1:\n    if 2:\n        pass\n    # comment\n    pass\n"
+        self.assertFormatEqual(contents_spc, fs(contents_spc))
+        self.assertFormatEqual(contents_spc, fs(contents_tab))

 
 

-    @patch("black.dump_to_file", dump_to_stderr)
-    def test_cantfit(self) -> None:
-        source, expected = read_data("cantfit")
-        actual = fs(source)
-        self.assertFormatEqual(expected, actual)
-        black.assert_equivalent(source, actual)
-        black.assert_stable(source, actual, black.FileMode())
+        contents_tab = "if 1:\n        if 2:\n\t\tpass\n\t\t# comment\n        pass\n"
+        contents_spc = "if 1:\n    if 2:\n        pass\n        # comment\n    pass\n"
+        self.assertFormatEqual(contents_spc, fs(contents_spc))
+        self.assertFormatEqual(contents_spc, fs(contents_tab))

 
 

-    @patch("black.dump_to_file", dump_to_stderr)
-    def test_import_spacing(self) -> None:
-        source, expected = read_data("import_spacing")
-        actual = fs(source)
-        self.assertFormatEqual(expected, actual)
-        black.assert_equivalent(source, actual)
-        black.assert_stable(source, actual, black.FileMode())
+    def test_report_verbose(self) -> None:
+        report = Report(verbose=True)
+        out_lines = []
+        err_lines = []

 
 

-    @patch("black.dump_to_file", dump_to_stderr)
-    def test_composition(self) -> None:
-        source, expected = read_data("composition")
-        actual = fs(source)
-        self.assertFormatEqual(expected, actual)
-        black.assert_equivalent(source, actual)
-        black.assert_stable(source, actual, black.FileMode())
+        def out(msg: str, **kwargs: Any) -> None:
+            out_lines.append(msg)

 
 

-    @patch("black.dump_to_file", dump_to_stderr)
-    def test_empty_lines(self) -> None:
-        source, expected = read_data("empty_lines")
-        actual = fs(source)
-        self.assertFormatEqual(expected, actual)
-        black.assert_equivalent(source, actual)
-        black.assert_stable(source, actual, black.FileMode())
+        def err(msg: str, **kwargs: Any) -> None:
+            err_lines.append(msg)

 
 

-    @patch("black.dump_to_file", dump_to_stderr)
-    def test_remove_parens(self) -> None:
-        source, expected = read_data("remove_parens")
-        actual = fs(source)
-        self.assertFormatEqual(expected, actual)
-        black.assert_equivalent(source, actual)
-        black.assert_stable(source, actual, black.FileMode())
-
-    @patch("black.dump_to_file", dump_to_stderr)
-    def test_string_prefixes(self) -> None:
-        source, expected = read_data("string_prefixes")
-        actual = fs(source)
-        self.assertFormatEqual(expected, actual)
-        black.assert_equivalent(source, actual)
-        black.assert_stable(source, actual, black.FileMode())
-
-    @patch("black.dump_to_file", dump_to_stderr)
-    def test_numeric_literals(self) -> None:
-        source, expected = read_data("numeric_literals")
-        mode = black.FileMode(target_versions=black.PY36_VERSIONS)
-        actual = fs(source, mode=mode)
-        self.assertFormatEqual(expected, actual)
-        black.assert_equivalent(source, actual)
-        black.assert_stable(source, actual, mode)
-
-    @patch("black.dump_to_file", dump_to_stderr)
-    def test_numeric_literals_ignoring_underscores(self) -> None:
-        source, expected = read_data("numeric_literals_skip_underscores")
-        mode = black.FileMode(target_versions=black.PY36_VERSIONS)
-        actual = fs(source, mode=mode)
-        self.assertFormatEqual(expected, actual)
-        black.assert_equivalent(source, actual)
-        black.assert_stable(source, actual, mode)
-
-    @patch("black.dump_to_file", dump_to_stderr)
-    def test_numeric_literals_py2(self) -> None:
-        source, expected = read_data("numeric_literals_py2")
-        actual = fs(source)
-        self.assertFormatEqual(expected, actual)
-        black.assert_stable(source, actual, black.FileMode())
-
-    @patch("black.dump_to_file", dump_to_stderr)
-    def test_python2(self) -> None:
-        source, expected = read_data("python2")
-        actual = fs(source)
-        self.assertFormatEqual(expected, actual)
-        black.assert_equivalent(source, actual)
-        black.assert_stable(source, actual, black.FileMode())
-
-    @patch("black.dump_to_file", dump_to_stderr)
-    def test_python2_print_function(self) -> None:
-        source, expected = read_data("python2_print_function")
-        mode = black.FileMode(target_versions={TargetVersion.PY27})
-        actual = fs(source, mode=mode)
-        self.assertFormatEqual(expected, actual)
-        black.assert_equivalent(source, actual)
-        black.assert_stable(source, actual, mode)
-
-    @patch("black.dump_to_file", dump_to_stderr)
-    def test_python2_unicode_literals(self) -> None:
-        source, expected = read_data("python2_unicode_literals")
-        actual = fs(source)
-        self.assertFormatEqual(expected, actual)
-        black.assert_equivalent(source, actual)
-        black.assert_stable(source, actual, black.FileMode())
-
-    @patch("black.dump_to_file", dump_to_stderr)
-    def test_stub(self) -> None:
-        mode = black.FileMode(is_pyi=True)
-        source, expected = read_data("stub.pyi")
-        actual = fs(source, mode=mode)
-        self.assertFormatEqual(expected, actual)
-        black.assert_stable(source, actual, mode)
-
-    @patch("black.dump_to_file", dump_to_stderr)
-    def test_async_as_identifier(self) -> None:
-        source_path = (THIS_DIR / "data" / "async_as_identifier.py").resolve()
-        source, expected = read_data("async_as_identifier")
-        actual = fs(source)
-        self.assertFormatEqual(expected, actual)
-        major, minor = sys.version_info[:2]
-        if major < 3 or (major <= 3 and minor < 7):
-            black.assert_equivalent(source, actual)
-        black.assert_stable(source, actual, black.FileMode())
-        # ensure black can parse this when the target is 3.6
-        self.invokeBlack([str(source_path), "--target-version", "py36"])
-        # but not on 3.7, because async/await is no longer an identifier
-        self.invokeBlack([str(source_path), "--target-version", "py37"], exit_code=123)
-
-    @patch("black.dump_to_file", dump_to_stderr)
-    def test_python37(self) -> None:
-        source_path = (THIS_DIR / "data" / "python37.py").resolve()
-        source, expected = read_data("python37")
-        actual = fs(source)
-        self.assertFormatEqual(expected, actual)
-        major, minor = sys.version_info[:2]
-        if major > 3 or (major == 3 and minor >= 7):
-            black.assert_equivalent(source, actual)
-        black.assert_stable(source, actual, black.FileMode())
-        # ensure black can parse this when the target is 3.7
-        self.invokeBlack([str(source_path), "--target-version", "py37"])
-        # but not on 3.6, because we use async as a reserved keyword
-        self.invokeBlack([str(source_path), "--target-version", "py36"], exit_code=123)
-
-    @patch("black.dump_to_file", dump_to_stderr)
-    def test_python38(self) -> None:
-        source, expected = read_data("python38")
-        actual = fs(source)
-        self.assertFormatEqual(expected, actual)
-        major, minor = sys.version_info[:2]
-        if major > 3 or (major == 3 and minor >= 8):
-            black.assert_equivalent(source, actual)
-        black.assert_stable(source, actual, black.FileMode())
-
-    @patch("black.dump_to_file", dump_to_stderr)
-    def test_fmtonoff(self) -> None:
-        source, expected = read_data("fmtonoff")
-        actual = fs(source)
-        self.assertFormatEqual(expected, actual)
-        black.assert_equivalent(source, actual)
-        black.assert_stable(source, actual, black.FileMode())
-
-    @patch("black.dump_to_file", dump_to_stderr)
-    def test_fmtonoff2(self) -> None:
-        source, expected = read_data("fmtonoff2")
-        actual = fs(source)
-        self.assertFormatEqual(expected, actual)
-        black.assert_equivalent(source, actual)
-        black.assert_stable(source, actual, black.FileMode())
-
-    @patch("black.dump_to_file", dump_to_stderr)
-    def test_fmtonoff3(self) -> None:
-        source, expected = read_data("fmtonoff3")
-        actual = fs(source)
-        self.assertFormatEqual(expected, actual)
-        black.assert_equivalent(source, actual)
-        black.assert_stable(source, actual, black.FileMode())
-
-    @patch("black.dump_to_file", dump_to_stderr)
-    def test_fmtonoff4(self) -> None:
-        source, expected = read_data("fmtonoff4")
-        actual = fs(source)
-        self.assertFormatEqual(expected, actual)
-        black.assert_equivalent(source, actual)
-        black.assert_stable(source, actual, black.FileMode())
-
-    @patch("black.dump_to_file", dump_to_stderr)
-    def test_remove_empty_parentheses_after_class(self) -> None:
-        source, expected = read_data("class_blank_parentheses")
-        actual = fs(source)
-        self.assertFormatEqual(expected, actual)
-        black.assert_equivalent(source, actual)
-        black.assert_stable(source, actual, black.FileMode())
-
-    @patch("black.dump_to_file", dump_to_stderr)
-    def test_new_line_between_class_and_code(self) -> None:
-        source, expected = read_data("class_methods_new_line")
-        actual = fs(source)
-        self.assertFormatEqual(expected, actual)
-        black.assert_equivalent(source, actual)
-        black.assert_stable(source, actual, black.FileMode())
-
-    @patch("black.dump_to_file", dump_to_stderr)
-    def test_bracket_match(self) -> None:
-        source, expected = read_data("bracketmatch")
-        actual = fs(source)
-        self.assertFormatEqual(expected, actual)
-        black.assert_equivalent(source, actual)
-        black.assert_stable(source, actual, black.FileMode())
-
-    @patch("black.dump_to_file", dump_to_stderr)
-    def test_tuple_assign(self) -> None:
-        source, expected = read_data("tupleassign")
-        actual = fs(source)
-        self.assertFormatEqual(expected, actual)
-        black.assert_equivalent(source, actual)
-        black.assert_stable(source, actual, black.FileMode())
-
-    @patch("black.dump_to_file", dump_to_stderr)
-    def test_beginning_backslash(self) -> None:
-        source, expected = read_data("beginning_backslash")
-        actual = fs(source)
-        self.assertFormatEqual(expected, actual)
-        black.assert_equivalent(source, actual)
-        black.assert_stable(source, actual, black.FileMode())
-
-    def test_tab_comment_indentation(self) -> None:
-        contents_tab = "if 1:\n\tif 2:\n\t\tpass\n\t# comment\n\tpass\n"
-        contents_spc = "if 1:\n    if 2:\n        pass\n    # comment\n    pass\n"
-        self.assertFormatEqual(contents_spc, fs(contents_spc))
-        self.assertFormatEqual(contents_spc, fs(contents_tab))
-
-        contents_tab = "if 1:\n\tif 2:\n\t\tpass\n\t\t# comment\n\tpass\n"
-        contents_spc = "if 1:\n    if 2:\n        pass\n        # comment\n    pass\n"
-        self.assertFormatEqual(contents_spc, fs(contents_spc))
-        self.assertFormatEqual(contents_spc, fs(contents_tab))
-
-        # mixed tabs and spaces (valid Python 2 code)
-        contents_tab = "if 1:\n        if 2:\n\t\tpass\n\t# comment\n        pass\n"
-        contents_spc = "if 1:\n    if 2:\n        pass\n    # comment\n    pass\n"
-        self.assertFormatEqual(contents_spc, fs(contents_spc))
-        self.assertFormatEqual(contents_spc, fs(contents_tab))
-
-        contents_tab = "if 1:\n        if 2:\n\t\tpass\n\t\t# comment\n        pass\n"
-        contents_spc = "if 1:\n    if 2:\n        pass\n        # comment\n    pass\n"
-        self.assertFormatEqual(contents_spc, fs(contents_spc))
-        self.assertFormatEqual(contents_spc, fs(contents_tab))
-
-    def test_report_verbose(self) -> None:
-        report = black.Report(verbose=True)
-        out_lines = []
-        err_lines = []
-
-        def out(msg: str, **kwargs: Any) -> None:
-            out_lines.append(msg)
-
-        def err(msg: str, **kwargs: Any) -> None:
-            err_lines.append(msg)
-
-        with patch("black.out", out), patch("black.err", err):
+        with patch("black.output._out", out), patch("black.output._err", err):

             report.done(Path("f1"), black.Changed.NO)
             self.assertEqual(len(out_lines), 1)
             self.assertEqual(len(err_lines), 0)
             report.done(Path("f1"), black.Changed.NO)
             self.assertEqual(len(out_lines), 1)
             self.assertEqual(len(err_lines), 0)


@@ -894,7 +501,7 @@ class BlackTestCase(unittest.TestCase):
             )
 
     def test_report_quiet(self) -> None:
             )
 
     def test_report_quiet(self) -> None:

-        report = black.Report(quiet=True)
+        report = Report(quiet=True)

         out_lines = []
         err_lines = []
 
         out_lines = []
         err_lines = []
 


@@ -904,7 +511,7 @@ class BlackTestCase(unittest.TestCase):
         def err(msg: str, **kwargs: Any) -> None:
             err_lines.append(msg)
 
         def err(msg: str, **kwargs: Any) -> None:
             err_lines.append(msg)
 

-        with patch("black.out", out), patch("black.err", err):
+        with patch("black.output._out", out), patch("black.output._err", err):

             report.done(Path("f1"), black.Changed.NO)
             self.assertEqual(len(out_lines), 0)
             self.assertEqual(len(err_lines), 0)
             report.done(Path("f1"), black.Changed.NO)
             self.assertEqual(len(out_lines), 0)
             self.assertEqual(len(err_lines), 0)


@@ -998,7 +605,7 @@ class BlackTestCase(unittest.TestCase):
         def err(msg: str, **kwargs: Any) -> None:
             err_lines.append(msg)
 
         def err(msg: str, **kwargs: Any) -> None:
             err_lines.append(msg)
 

-        with patch("black.out", out), patch("black.err", err):
+        with patch("black.output._out", out), patch("black.output._err", err):

             report.done(Path("f1"), black.Changed.NO)
             self.assertEqual(len(out_lines), 0)
             self.assertEqual(len(err_lines), 0)
             report.done(Path("f1"), black.Changed.NO)
             self.assertEqual(len(out_lines), 0)
             self.assertEqual(len(err_lines), 0)


@@ -1090,24 +697,48 @@ class BlackTestCase(unittest.TestCase):
 
         straddling = "x + y"
         black.lib2to3_parse(straddling)
 
         straddling = "x + y"
         black.lib2to3_parse(straddling)

-        black.lib2to3_parse(straddling, {TargetVersion.PY27})

         black.lib2to3_parse(straddling, {TargetVersion.PY36})
         black.lib2to3_parse(straddling, {TargetVersion.PY36})

-        black.lib2to3_parse(straddling, {TargetVersion.PY27, TargetVersion.PY36})

 
         py2_only = "print x"
 
         py2_only = "print x"

-        black.lib2to3_parse(py2_only)
-        black.lib2to3_parse(py2_only, {TargetVersion.PY27})

         with self.assertRaises(black.InvalidInput):
             black.lib2to3_parse(py2_only, {TargetVersion.PY36})
         with self.assertRaises(black.InvalidInput):
             black.lib2to3_parse(py2_only, {TargetVersion.PY36})

-        with self.assertRaises(black.InvalidInput):
-            black.lib2to3_parse(py2_only, {TargetVersion.PY27, TargetVersion.PY36})

 
         py3_only = "exec(x, end=y)"
         black.lib2to3_parse(py3_only)
 
         py3_only = "exec(x, end=y)"
         black.lib2to3_parse(py3_only)

-        with self.assertRaises(black.InvalidInput):
-            black.lib2to3_parse(py3_only, {TargetVersion.PY27})

         black.lib2to3_parse(py3_only, {TargetVersion.PY36})
         black.lib2to3_parse(py3_only, {TargetVersion.PY36})

-        black.lib2to3_parse(py3_only, {TargetVersion.PY27, TargetVersion.PY36})
+
+    def test_get_features_used_decorator(self) -> None:
+        # Test the feature detection of new decorator syntax
+        # since this makes some test cases of test_get_features_used()
+        # fails if it fails, this is tested first so that a useful case
+        # is identified
+        simples, relaxed = read_data("decorators")
+        # skip explanation comments at the top of the file
+        for simple_test in simples.split("##")[1:]:
+            node = black.lib2to3_parse(simple_test)
+            decorator = str(node.children[0].children[0]).strip()
+            self.assertNotIn(
+                Feature.RELAXED_DECORATORS,
+                black.get_features_used(node),
+                msg=(
+                    f"decorator '{decorator}' follows python<=3.8 syntax"
+                    "but is detected as 3.9+"
+                    # f"The full node is\n{node!r}"
+                ),
+            )
+        # skip the '# output' comment at the top of the output part
+        for relaxed_test in relaxed.split("##")[1:]:
+            node = black.lib2to3_parse(relaxed_test)
+            decorator = str(node.children[0].children[0]).strip()
+            self.assertIn(
+                Feature.RELAXED_DECORATORS,
+                black.get_features_used(node),
+                msg=(
+                    f"decorator '{decorator}' uses python3.9+ syntax"
+                    "but is detected as python<=3.8"
+                    # f"The full node is\n{node!r}"
+                ),
+            )

 
     def test_get_features_used(self) -> None:
         node = black.lib2to3_parse("def f(*, arg): ...\n")
 
     def test_get_features_used(self) -> None:
         node = black.lib2to3_parse("def f(*, arg): ...\n")


@@ -1139,6 +770,48 @@ class BlackTestCase(unittest.TestCase):
         self.assertEqual(black.get_features_used(node), set())
         node = black.lib2to3_parse(expected)
         self.assertEqual(black.get_features_used(node), set())
         self.assertEqual(black.get_features_used(node), set())
         node = black.lib2to3_parse(expected)
         self.assertEqual(black.get_features_used(node), set())

+        node = black.lib2to3_parse("lambda a, /, b: ...")
+        self.assertEqual(black.get_features_used(node), {Feature.POS_ONLY_ARGUMENTS})
+        node = black.lib2to3_parse("def fn(a, /, b): ...")
+        self.assertEqual(black.get_features_used(node), {Feature.POS_ONLY_ARGUMENTS})
+        node = black.lib2to3_parse("def fn(): yield a, b")
+        self.assertEqual(black.get_features_used(node), set())
+        node = black.lib2to3_parse("def fn(): return a, b")
+        self.assertEqual(black.get_features_used(node), set())
+        node = black.lib2to3_parse("def fn(): yield *b, c")
+        self.assertEqual(black.get_features_used(node), {Feature.UNPACKING_ON_FLOW})
+        node = black.lib2to3_parse("def fn(): return a, *b, c")
+        self.assertEqual(black.get_features_used(node), {Feature.UNPACKING_ON_FLOW})
+        node = black.lib2to3_parse("x = a, *b, c")
+        self.assertEqual(black.get_features_used(node), set())
+        node = black.lib2to3_parse("x: Any = regular")
+        self.assertEqual(black.get_features_used(node), set())
+        node = black.lib2to3_parse("x: Any = (regular, regular)")
+        self.assertEqual(black.get_features_used(node), set())
+        node = black.lib2to3_parse("x: Any = Complex(Type(1))[something]")
+        self.assertEqual(black.get_features_used(node), set())
+        node = black.lib2to3_parse("x: Tuple[int, ...] = a, b, c")
+        self.assertEqual(
+            black.get_features_used(node), {Feature.ANN_ASSIGN_EXTENDED_RHS}
+        )
+
+    def test_get_features_used_for_future_flags(self) -> None:
+        for src, features in [
+            ("from __future__ import annotations", {Feature.FUTURE_ANNOTATIONS}),
+            (
+                "from __future__ import (other, annotations)",
+                {Feature.FUTURE_ANNOTATIONS},
+            ),
+            ("a = 1 + 2\nfrom something import annotations", set()),
+            ("from __future__ import x, y", set()),
+        ]:
+            with self.subTest(src=src, features=features):
+                node = black.lib2to3_parse(src)
+                future_imports = black.get_future_imports(node)
+                self.assertEqual(
+                    black.get_features_used(node, future_imports=future_imports),
+                    features,
+                )

 
     def test_get_future_imports(self) -> None:
         node = black.lib2to3_parse("\n")
 
     def test_get_future_imports(self) -> None:
         node = black.lib2to3_parse("\n")


@@ -1170,6 +843,7 @@ class BlackTestCase(unittest.TestCase):
         )
         self.assertEqual({"unicode_literals", "print"}, black.get_future_imports(node))
 
         )
         self.assertEqual({"unicode_literals", "print"}, black.get_future_imports(node))
 

+    @pytest.mark.incompatible_with_mypyc

     def test_debug_visitor(self) -> None:
         source, _ = read_data("debug_visitor.py")
         expected, _ = read_data("debug_visitor.out")
     def test_debug_visitor(self) -> None:
         source, _ = read_data("debug_visitor.py")
         expected, _ = read_data("debug_visitor.out")


@@ -1182,8 +856,8 @@ class BlackTestCase(unittest.TestCase):
         def err(msg: str, **kwargs: Any) -> None:
             err_lines.append(msg)
 
         def err(msg: str, **kwargs: Any) -> None:
             err_lines.append(msg)
 

-        with patch("black.out", out), patch("black.err", err):
-            black.DebugVisitor.show(source)
+        with patch("black.debug.out", out):
+            DebugVisitor.show(source)

         actual = "\n".join(out_lines) + "\n"
         log_name = ""
         if expected != actual:
         actual = "\n".join(out_lines) + "\n"
         log_name = ""
         if expected != actual:


@@ -1196,7 +870,7 @@ class BlackTestCase(unittest.TestCase):
 
     def test_format_file_contents(self) -> None:
         empty = ""
 
     def test_format_file_contents(self) -> None:
         empty = ""

-        mode = black.FileMode()
+        mode = DEFAULT_MODE

         with self.assertRaises(black.NothingChanged):
             black.format_file_contents(empty, mode=mode, fast=False)
         just_nl = "\n"
         with self.assertRaises(black.NothingChanged):
             black.format_file_contents(empty, mode=mode, fast=False)
         just_nl = "\n"


@@ -1220,6 +894,7 @@ class BlackTestCase(unittest.TestCase):
         self.assertEqual(len(n.children), 1)
         self.assertEqual(n.children[0].type, black.token.ENDMARKER)
 
         self.assertEqual(len(n.children), 1)
         self.assertEqual(n.children[0].type, black.token.ENDMARKER)
 

+    @pytest.mark.incompatible_with_mypyc

     @unittest.skipIf(os.environ.get("SKIP_AST_PRINT"), "user set SKIP_AST_PRINT")
     def test_assertFormatEqual(self) -> None:
         out_lines = []
     @unittest.skipIf(os.environ.get("SKIP_AST_PRINT"), "user set SKIP_AST_PRINT")
     def test_assertFormatEqual(self) -> None:
         out_lines = []


@@ -1231,202 +906,57 @@ class BlackTestCase(unittest.TestCase):
         def err(msg: str, **kwargs: Any) -> None:
             err_lines.append(msg)
 
         def err(msg: str, **kwargs: Any) -> None:
             err_lines.append(msg)
 

-        with patch("black.out", out), patch("black.err", err):
+        with patch("black.output._out", out), patch("black.output._err", err):

             with self.assertRaises(AssertionError):
                 self.assertFormatEqual("j = [1, 2, 3]", "j = [1, 2, 3,]")
 
         out_str = "".join(out_lines)
             with self.assertRaises(AssertionError):
                 self.assertFormatEqual("j = [1, 2, 3]", "j = [1, 2, 3,]")
 
         out_str = "".join(out_lines)

-        self.assertTrue("Expected tree:" in out_str)
-        self.assertTrue("Actual tree:" in out_str)
+        self.assertIn("Expected tree:", out_str)
+        self.assertIn("Actual tree:", out_str)

         self.assertEqual("".join(err_lines), "")
 
         self.assertEqual("".join(err_lines), "")
 

-    def test_cache_broken_file(self) -> None:
-        mode = black.FileMode()
-        with cache_dir() as workspace:
-            cache_file = black.get_cache_file(mode)
-            with cache_file.open("w") as fobj:
-                fobj.write("this is not a pickle")
-            self.assertEqual(black.read_cache(mode), {})
-            src = (workspace / "test.py").resolve()
-            with src.open("w") as fobj:
-                fobj.write("print('hello')")
-            self.invokeBlack([str(src)])
-            cache = black.read_cache(mode)
-            self.assertIn(src, cache)
-
-    def test_cache_single_file_already_cached(self) -> None:
-        mode = black.FileMode()
-        with cache_dir() as workspace:
-            src = (workspace / "test.py").resolve()
-            with src.open("w") as fobj:
-                fobj.write("print('hello')")
-            black.write_cache({}, [src], mode)
-            self.invokeBlack([str(src)])
-            with src.open("r") as fobj:
-                self.assertEqual(fobj.read(), "print('hello')")
-

     @event_loop()
     @event_loop()

-    def test_cache_multiple_files(self) -> None:
-        mode = black.FileMode()
-        with cache_dir() as workspace, patch(
-            "black.ProcessPoolExecutor", new=ThreadPoolExecutor
-        ):
-            one = (workspace / "one.py").resolve()
-            with one.open("w") as fobj:
-                fobj.write("print('hello')")
-            two = (workspace / "two.py").resolve()
-            with two.open("w") as fobj:
-                fobj.write("print('hello')")
-            black.write_cache({}, [one], mode)
+    @patch("black.ProcessPoolExecutor", MagicMock(side_effect=OSError))
+    def test_works_in_mono_process_only_environment(self) -> None:
+        with cache_dir() as workspace:
+            for f in [
+                (workspace / "one.py").resolve(),
+                (workspace / "two.py").resolve(),
+            ]:
+                f.write_text('print("hello")\n')

             self.invokeBlack([str(workspace)])
             self.invokeBlack([str(workspace)])

-            with one.open("r") as fobj:
-                self.assertEqual(fobj.read(), "print('hello')")
-            with two.open("r") as fobj:
-                self.assertEqual(fobj.read(), 'print("hello")\n')
-            cache = black.read_cache(mode)
-            self.assertIn(one, cache)
-            self.assertIn(two, cache)

 
 

-    def test_no_cache_when_writeback_diff(self) -> None:
-        mode = black.FileMode()
-        with cache_dir() as workspace:
-            src = (workspace / "test.py").resolve()
-            with src.open("w") as fobj:
-                fobj.write("print('hello')")
-            self.invokeBlack([str(src), "--diff"])
-            cache_file = black.get_cache_file(mode)
-            self.assertFalse(cache_file.exists())
+    @event_loop()
+    def test_check_diff_use_together(self) -> None:
+        with cache_dir():
+            # Files which will be reformatted.
+            src1 = (THIS_DIR / "data" / "string_quotes.py").resolve()
+            self.invokeBlack([str(src1), "--diff", "--check"], exit_code=1)
+            # Files which will not be reformatted.
+            src2 = (THIS_DIR / "data" / "composition.py").resolve()
+            self.invokeBlack([str(src2), "--diff", "--check"])
+            # Multi file command.
+            self.invokeBlack([str(src1), str(src2), "--diff", "--check"], exit_code=1)

 
 

-    def test_no_cache_when_stdin(self) -> None:
-        mode = black.FileMode()
+    def test_no_src_fails(self) -> None:

         with cache_dir():
         with cache_dir():

-            result = CliRunner().invoke(
-                black.main, ["-"], input=BytesIO(b"print('hello')")
-            )
-            self.assertEqual(result.exit_code, 0)
-            cache_file = black.get_cache_file(mode)
-            self.assertFalse(cache_file.exists())
+            self.invokeBlack([], exit_code=1)

 
 

-    def test_read_cache_no_cachefile(self) -> None:
-        mode = black.FileMode()
+    def test_src_and_code_fails(self) -> None:

         with cache_dir():
         with cache_dir():

-            self.assertEqual(black.read_cache(mode), {})
+            self.invokeBlack([".", "-c", "0"], exit_code=1)

 
 

-    def test_write_cache_read_cache(self) -> None:
-        mode = black.FileMode()
+    def test_broken_symlink(self) -> None:

         with cache_dir() as workspace:
         with cache_dir() as workspace:

-            src = (workspace / "test.py").resolve()
-            src.touch()
-            black.write_cache({}, [src], mode)
-            cache = black.read_cache(mode)
-            self.assertIn(src, cache)
-            self.assertEqual(cache[src], black.get_cache_info(src))
-
-    def test_filter_cached(self) -> None:
-        with TemporaryDirectory() as workspace:
-            path = Path(workspace)
-            uncached = (path / "uncached").resolve()
-            cached = (path / "cached").resolve()
-            cached_but_changed = (path / "changed").resolve()
-            uncached.touch()
-            cached.touch()
-            cached_but_changed.touch()
-            cache = {cached: black.get_cache_info(cached), cached_but_changed: (0.0, 0)}
-            todo, done = black.filter_cached(
-                cache, {uncached, cached, cached_but_changed}
-            )
-            self.assertEqual(todo, {uncached, cached_but_changed})
-            self.assertEqual(done, {cached})
-
-    def test_write_cache_creates_directory_if_needed(self) -> None:
-        mode = black.FileMode()
-        with cache_dir(exists=False) as workspace:
-            self.assertFalse(workspace.exists())
-            black.write_cache({}, [], mode)
-            self.assertTrue(workspace.exists())
-
-    @event_loop()
-    def test_failed_formatting_does_not_get_cached(self) -> None:
-        mode = black.FileMode()
-        with cache_dir() as workspace, patch(
-            "black.ProcessPoolExecutor", new=ThreadPoolExecutor
-        ):
-            failing = (workspace / "failing.py").resolve()
-            with failing.open("w") as fobj:
-                fobj.write("not actually python")
-            clean = (workspace / "clean.py").resolve()
-            with clean.open("w") as fobj:
-                fobj.write('print("hello")\n')
-            self.invokeBlack([str(workspace)], exit_code=123)
-            cache = black.read_cache(mode)
-            self.assertNotIn(failing, cache)
-            self.assertIn(clean, cache)
-
-    def test_write_cache_write_fail(self) -> None:
-        mode = black.FileMode()
-        with cache_dir(), patch.object(Path, "open") as mock:
-            mock.side_effect = OSError
-            black.write_cache({}, [], mode)
-
-    @event_loop()
-    @patch("black.ProcessPoolExecutor", MagicMock(side_effect=OSError))
-    def test_works_in_mono_process_only_environment(self) -> None:
-        with cache_dir() as workspace:
-            for f in [
-                (workspace / "one.py").resolve(),
-                (workspace / "two.py").resolve(),
-            ]:
-                f.write_text('print("hello")\n')
-            self.invokeBlack([str(workspace)])
-
-    @event_loop()
-    def test_check_diff_use_together(self) -> None:
-        with cache_dir():
-            # Files which will be reformatted.
-            src1 = (THIS_DIR / "data" / "string_quotes.py").resolve()
-            self.invokeBlack([str(src1), "--diff", "--check"], exit_code=1)
-            # Files which will not be reformatted.
-            src2 = (THIS_DIR / "data" / "composition.py").resolve()
-            self.invokeBlack([str(src2), "--diff", "--check"])
-            # Multi file command.
-            self.invokeBlack([str(src1), str(src2), "--diff", "--check"], exit_code=1)
-
-    def test_no_files(self) -> None:
-        with cache_dir():
-            # Without an argument, black exits with error code 0.
-            self.invokeBlack([])
-
-    def test_broken_symlink(self) -> None:
-        with cache_dir() as workspace:
-            symlink = workspace / "broken_link.py"
-            try:
-                symlink.symlink_to("nonexistent.py")
-            except OSError as e:
-                self.skipTest(f"Can't create symlinks: {e}")
-            self.invokeBlack([str(workspace.resolve())])
-
-    def test_read_cache_line_lengths(self) -> None:
-        mode = black.FileMode()
-        short_mode = black.FileMode(line_length=1)
-        with cache_dir() as workspace:
-            path = (workspace / "file.py").resolve()
-            path.touch()
-            black.write_cache({}, [path], mode)
-            one = black.read_cache(mode)
-            self.assertIn(path, one)
-            two = black.read_cache(short_mode)
-            self.assertNotIn(path, two)
-
-    def test_tricky_unicode_symbols(self) -> None:
-        source, expected = read_data("tricky_unicode_symbols")
-        actual = fs(source)
-        self.assertFormatEqual(expected, actual)
-        black.assert_equivalent(source, actual)
-        black.assert_stable(source, actual, black.FileMode())
+            symlink = workspace / "broken_link.py"
+            try:
+                symlink.symlink_to("nonexistent.py")
+            except (OSError, NotImplementedError) as e:
+                self.skipTest(f"Can't create symlinks: {e}")
+            self.invokeBlack([str(workspace.resolve())])

 
     def test_single_file_force_pyi(self) -> None:
 
     def test_single_file_force_pyi(self) -> None:

-        reg_mode = black.FileMode()
-        pyi_mode = black.FileMode(is_pyi=True)
+        pyi_mode = replace(DEFAULT_MODE, is_pyi=True)

         contents, expected = read_data("force_pyi")
         with cache_dir() as workspace:
             path = (workspace / "file.py").resolve()
         contents, expected = read_data("force_pyi")
         with cache_dir() as workspace:
             path = (workspace / "file.py").resolve()


@@ -1437,15 +967,17 @@ class BlackTestCase(unittest.TestCase):
                 actual = fh.read()
             # verify cache with --pyi is separate
             pyi_cache = black.read_cache(pyi_mode)
                 actual = fh.read()
             # verify cache with --pyi is separate
             pyi_cache = black.read_cache(pyi_mode)

-            self.assertIn(path, pyi_cache)
-            normal_cache = black.read_cache(reg_mode)
-            self.assertNotIn(path, normal_cache)
-        self.assertEqual(actual, expected)
+            self.assertIn(str(path), pyi_cache)
+            normal_cache = black.read_cache(DEFAULT_MODE)
+            self.assertNotIn(str(path), normal_cache)
+        self.assertFormatEqual(expected, actual)
+        black.assert_equivalent(contents, actual)
+        black.assert_stable(contents, actual, pyi_mode)

 
     @event_loop()
     def test_multi_file_force_pyi(self) -> None:
 
     @event_loop()
     def test_multi_file_force_pyi(self) -> None:

-        reg_mode = black.FileMode()
-        pyi_mode = black.FileMode(is_pyi=True)
+        reg_mode = DEFAULT_MODE
+        pyi_mode = replace(DEFAULT_MODE, is_pyi=True)

         contents, expected = read_data("force_pyi")
         with cache_dir() as workspace:
             paths = [
         contents, expected = read_data("force_pyi")
         with cache_dir() as workspace:
             paths = [


@@ -1464,8 +996,8 @@ class BlackTestCase(unittest.TestCase):
             pyi_cache = black.read_cache(pyi_mode)
             normal_cache = black.read_cache(reg_mode)
             for path in paths:
             pyi_cache = black.read_cache(pyi_mode)
             normal_cache = black.read_cache(reg_mode)
             for path in paths:

-                self.assertIn(path, pyi_cache)
-                self.assertNotIn(path, normal_cache)
+                self.assertIn(str(path), pyi_cache)
+                self.assertNotIn(str(path), normal_cache)

 
     def test_pipe_force_pyi(self) -> None:
         source, expected = read_data("force_pyi")
 
     def test_pipe_force_pyi(self) -> None:
         source, expected = read_data("force_pyi")


@@ -1477,8 +1009,8 @@ class BlackTestCase(unittest.TestCase):
         self.assertFormatEqual(actual, expected)
 
     def test_single_file_force_py36(self) -> None:
         self.assertFormatEqual(actual, expected)
 
     def test_single_file_force_py36(self) -> None:

-        reg_mode = black.FileMode()
-        py36_mode = black.FileMode(target_versions=black.PY36_VERSIONS)
+        reg_mode = DEFAULT_MODE
+        py36_mode = replace(DEFAULT_MODE, target_versions=PY36_VERSIONS)

         source, expected = read_data("force_py36")
         with cache_dir() as workspace:
             path = (workspace / "file.py").resolve()
         source, expected = read_data("force_py36")
         with cache_dir() as workspace:
             path = (workspace / "file.py").resolve()


@@ -1489,15 +1021,15 @@ class BlackTestCase(unittest.TestCase):
                 actual = fh.read()
             # verify cache with --target-version is separate
             py36_cache = black.read_cache(py36_mode)
                 actual = fh.read()
             # verify cache with --target-version is separate
             py36_cache = black.read_cache(py36_mode)

-            self.assertIn(path, py36_cache)
+            self.assertIn(str(path), py36_cache)

             normal_cache = black.read_cache(reg_mode)
             normal_cache = black.read_cache(reg_mode)

-            self.assertNotIn(path, normal_cache)
+            self.assertNotIn(str(path), normal_cache)

         self.assertEqual(actual, expected)
 
     @event_loop()
     def test_multi_file_force_py36(self) -> None:
         self.assertEqual(actual, expected)
 
     @event_loop()
     def test_multi_file_force_py36(self) -> None:

-        reg_mode = black.FileMode()
-        py36_mode = black.FileMode(target_versions=black.PY36_VERSIONS)
+        reg_mode = DEFAULT_MODE
+        py36_mode = replace(DEFAULT_MODE, target_versions=PY36_VERSIONS)

         source, expected = read_data("force_py36")
         with cache_dir() as workspace:
             paths = [
         source, expected = read_data("force_py36")
         with cache_dir() as workspace:
             paths = [


@@ -1516,15 +1048,8 @@ class BlackTestCase(unittest.TestCase):
             pyi_cache = black.read_cache(py36_mode)
             normal_cache = black.read_cache(reg_mode)
             for path in paths:
             pyi_cache = black.read_cache(py36_mode)
             normal_cache = black.read_cache(reg_mode)
             for path in paths:

-                self.assertIn(path, pyi_cache)
-                self.assertNotIn(path, normal_cache)
-
-    def test_collections(self) -> None:
-        source, expected = read_data("collections")
-        actual = fs(source)
-        self.assertFormatEqual(expected, actual)
-        black.assert_equivalent(source, actual)
-        black.assert_stable(source, actual, black.FileMode())
+                self.assertIn(str(path), pyi_cache)
+                self.assertNotIn(str(path), normal_cache)

 
     def test_pipe_force_py36(self) -> None:
         source, expected = read_data("force_py36")
 
     def test_pipe_force_py36(self) -> None:
         source, expected = read_data("force_py36")


@@ -1537,106 +1062,168 @@ class BlackTestCase(unittest.TestCase):
         actual = result.output
         self.assertFormatEqual(actual, expected)
 
         actual = result.output
         self.assertFormatEqual(actual, expected)
 

-    def test_include_exclude(self) -> None:
-        path = THIS_DIR / "data" / "include_exclude_tests"
-        include = re.compile(r"\.pyi?$")
-        exclude = re.compile(r"/exclude/|/\.definitely_exclude/")
-        report = black.Report()
-        gitignore = PathSpec.from_lines("gitwildmatch", [])
-        sources: List[Path] = []
-        expected = [
-            Path(path / "b/dont_exclude/a.py"),
-            Path(path / "b/dont_exclude/a.pyi"),
-        ]
-        this_abs = THIS_DIR.resolve()
-        sources.extend(
-            black.gen_python_files(
-                path.iterdir(), this_abs, include, [exclude], report, gitignore
+    @pytest.mark.incompatible_with_mypyc
+    def test_reformat_one_with_stdin(self) -> None:
+        with patch(
+            "black.format_stdin_to_stdout",
+            return_value=lambda *args, **kwargs: black.Changed.YES,
+        ) as fsts:
+            report = MagicMock()
+            path = Path("-")
+            black.reformat_one(
+                path,
+                fast=True,
+                write_back=black.WriteBack.YES,
+                mode=DEFAULT_MODE,
+                report=report,

             )
             )

-        )
-        self.assertEqual(sorted(expected), sorted(sources))
-
-    def test_gitignore_exclude(self) -> None:
-        path = THIS_DIR / "data" / "include_exclude_tests"
-        include = re.compile(r"\.pyi?$")
-        exclude = re.compile(r"")
-        report = black.Report()
-        gitignore = PathSpec.from_lines(
-            "gitwildmatch", ["exclude/", ".definitely_exclude"]
-        )
-        sources: List[Path] = []
-        expected = [
-            Path(path / "b/dont_exclude/a.py"),
-            Path(path / "b/dont_exclude/a.pyi"),
-        ]
-        this_abs = THIS_DIR.resolve()
-        sources.extend(
-            black.gen_python_files(
-                path.iterdir(), this_abs, include, [exclude], report, gitignore
+            fsts.assert_called_once()
+            report.done.assert_called_with(path, black.Changed.YES)
+
+    @pytest.mark.incompatible_with_mypyc
+    def test_reformat_one_with_stdin_filename(self) -> None:
+        with patch(
+            "black.format_stdin_to_stdout",
+            return_value=lambda *args, **kwargs: black.Changed.YES,
+        ) as fsts:
+            report = MagicMock()
+            p = "foo.py"
+            path = Path(f"__BLACK_STDIN_FILENAME__{p}")
+            expected = Path(p)
+            black.reformat_one(
+                path,
+                fast=True,
+                write_back=black.WriteBack.YES,
+                mode=DEFAULT_MODE,
+                report=report,

             )
             )

+            fsts.assert_called_once_with(
+                fast=True, write_back=black.WriteBack.YES, mode=DEFAULT_MODE
+            )
+            # __BLACK_STDIN_FILENAME__ should have been stripped
+            report.done.assert_called_with(expected, black.Changed.YES)
+
+    @pytest.mark.incompatible_with_mypyc
+    def test_reformat_one_with_stdin_filename_pyi(self) -> None:
+        with patch(
+            "black.format_stdin_to_stdout",
+            return_value=lambda *args, **kwargs: black.Changed.YES,
+        ) as fsts:
+            report = MagicMock()
+            p = "foo.pyi"
+            path = Path(f"__BLACK_STDIN_FILENAME__{p}")
+            expected = Path(p)
+            black.reformat_one(
+                path,
+                fast=True,
+                write_back=black.WriteBack.YES,
+                mode=DEFAULT_MODE,
+                report=report,
+            )
+            fsts.assert_called_once_with(
+                fast=True,
+                write_back=black.WriteBack.YES,
+                mode=replace(DEFAULT_MODE, is_pyi=True),
+            )
+            # __BLACK_STDIN_FILENAME__ should have been stripped
+            report.done.assert_called_with(expected, black.Changed.YES)
+
+    @pytest.mark.incompatible_with_mypyc
+    def test_reformat_one_with_stdin_filename_ipynb(self) -> None:
+        with patch(
+            "black.format_stdin_to_stdout",
+            return_value=lambda *args, **kwargs: black.Changed.YES,
+        ) as fsts:
+            report = MagicMock()
+            p = "foo.ipynb"
+            path = Path(f"__BLACK_STDIN_FILENAME__{p}")
+            expected = Path(p)
+            black.reformat_one(
+                path,
+                fast=True,
+                write_back=black.WriteBack.YES,
+                mode=DEFAULT_MODE,
+                report=report,
+            )
+            fsts.assert_called_once_with(
+                fast=True,
+                write_back=black.WriteBack.YES,
+                mode=replace(DEFAULT_MODE, is_ipynb=True),
+            )
+            # __BLACK_STDIN_FILENAME__ should have been stripped
+            report.done.assert_called_with(expected, black.Changed.YES)
+
+    @pytest.mark.incompatible_with_mypyc
+    def test_reformat_one_with_stdin_and_existing_path(self) -> None:
+        with patch(
+            "black.format_stdin_to_stdout",
+            return_value=lambda *args, **kwargs: black.Changed.YES,
+        ) as fsts:
+            report = MagicMock()
+            # Even with an existing file, since we are forcing stdin, black
+            # should output to stdout and not modify the file inplace
+            p = Path(str(THIS_DIR / "data/collections.py"))
+            # Make sure is_file actually returns True
+            self.assertTrue(p.is_file())
+            path = Path(f"__BLACK_STDIN_FILENAME__{p}")
+            expected = Path(p)
+            black.reformat_one(
+                path,
+                fast=True,
+                write_back=black.WriteBack.YES,
+                mode=DEFAULT_MODE,
+                report=report,
+            )
+            fsts.assert_called_once()
+            # __BLACK_STDIN_FILENAME__ should have been stripped
+            report.done.assert_called_with(expected, black.Changed.YES)
+
+    def test_reformat_one_with_stdin_empty(self) -> None:
+        output = io.StringIO()
+        with patch("io.TextIOWrapper", lambda *args, **kwargs: output):
+            try:
+                black.format_stdin_to_stdout(
+                    fast=True,
+                    content="",
+                    write_back=black.WriteBack.YES,
+                    mode=DEFAULT_MODE,
+                )
+            except io.UnsupportedOperation:
+                pass  # StringIO does not support detach
+            assert output.getvalue() == ""
+
+    def test_invalid_cli_regex(self) -> None:
+        for option in ["--include", "--exclude", "--extend-exclude", "--force-exclude"]:
+            self.invokeBlack(["-", option, "**()(!!*)"], exit_code=2)
+
+    def test_required_version_matches_version(self) -> None:
+        self.invokeBlack(
+            ["--required-version", black.__version__, "-c", "0"],
+            exit_code=0,
+            ignore_config=True,

         )
         )

-        self.assertEqual(sorted(expected), sorted(sources))

 
 

-    def test_empty_include(self) -> None:
-        path = THIS_DIR / "data" / "include_exclude_tests"
-        report = black.Report()
-        gitignore = PathSpec.from_lines("gitwildmatch", [])
-        empty = re.compile(r"")
-        sources: List[Path] = []
-        expected = [
-            Path(path / "b/exclude/a.pie"),
-            Path(path / "b/exclude/a.py"),
-            Path(path / "b/exclude/a.pyi"),
-            Path(path / "b/dont_exclude/a.pie"),
-            Path(path / "b/dont_exclude/a.py"),
-            Path(path / "b/dont_exclude/a.pyi"),
-            Path(path / "b/.definitely_exclude/a.pie"),
-            Path(path / "b/.definitely_exclude/a.py"),
-            Path(path / "b/.definitely_exclude/a.pyi"),
-        ]
-        this_abs = THIS_DIR.resolve()
-        sources.extend(
-            black.gen_python_files(
-                path.iterdir(),
-                this_abs,
-                empty,
-                [re.compile(black.DEFAULT_EXCLUDES)],
-                report,
-                gitignore,
-            )
+    def test_required_version_matches_partial_version(self) -> None:
+        self.invokeBlack(
+            ["--required-version", black.__version__.split(".")[0], "-c", "0"],
+            exit_code=0,
+            ignore_config=True,

         )
         )

-        self.assertEqual(sorted(expected), sorted(sources))

 
 

-    def test_empty_exclude(self) -> None:
-        path = THIS_DIR / "data" / "include_exclude_tests"
-        report = black.Report()
-        gitignore = PathSpec.from_lines("gitwildmatch", [])
-        empty = re.compile(r"")
-        sources: List[Path] = []
-        expected = [
-            Path(path / "b/dont_exclude/a.py"),
-            Path(path / "b/dont_exclude/a.pyi"),
-            Path(path / "b/exclude/a.py"),
-            Path(path / "b/exclude/a.pyi"),
-            Path(path / "b/.definitely_exclude/a.py"),
-            Path(path / "b/.definitely_exclude/a.pyi"),
-        ]
-        this_abs = THIS_DIR.resolve()
-        sources.extend(
-            black.gen_python_files(
-                path.iterdir(),
-                this_abs,
-                re.compile(black.DEFAULT_INCLUDES),
-                [empty],
-                report,
-                gitignore,
-            )
+    def test_required_version_does_not_match_on_minor_version(self) -> None:
+        self.invokeBlack(
+            ["--required-version", black.__version__.split(".")[0] + ".999", "-c", "0"],
+            exit_code=1,
+            ignore_config=True,

         )
         )

-        self.assertEqual(sorted(expected), sorted(sources))

 
 

-    def test_invalid_include_exclude(self) -> None:
-        for option in ["--include", "--exclude"]:
-            self.invokeBlack(["-", option, "**()(!!*)"], exit_code=2)
+    def test_required_version_does_not_match_version(self) -> None:
+        result = BlackRunner().invoke(
+            black.main,
+            ["--required-version", "20.99b", "-c", "0"],
+        )
+        self.assertEqual(result.exit_code, 1)
+        self.assertIn("required version", result.stderr)

 
     def test_preserves_line_endings(self) -> None:
         with TemporaryDirectory() as workspace:
 
     def test_preserves_line_endings(self) -> None:
         with TemporaryDirectory() as workspace:


@@ -1658,7 +1245,7 @@ class BlackTestCase(unittest.TestCase):
                 black.main, ["-", "--fast"], input=BytesIO(contents.encode("utf8"))
             )
             self.assertEqual(result.exit_code, 0)
                 black.main, ["-", "--fast"], input=BytesIO(contents.encode("utf8"))
             )
             self.assertEqual(result.exit_code, 0)

-            output = runner.stdout_bytes
+            output = result.stdout_bytes

             self.assertIn(nl.encode("utf8"), output)
             if nl == "\n":
                 self.assertNotIn(b"\r\n", output)
             self.assertIn(nl.encode("utf8"), output)
             if nl == "\n":
                 self.assertNotIn(b"\r\n", output)


@@ -1667,50 +1254,9 @@ class BlackTestCase(unittest.TestCase):
         with self.assertRaises(AssertionError):
             black.assert_equivalent("{}", "None")
 
         with self.assertRaises(AssertionError):
             black.assert_equivalent("{}", "None")
 

-    def test_symlink_out_of_root_directory(self) -> None:
-        path = MagicMock()
-        root = THIS_DIR.resolve()
-        child = MagicMock()
-        include = re.compile(black.DEFAULT_INCLUDES)
-        exclude = re.compile(black.DEFAULT_EXCLUDES)
-        report = black.Report()
-        gitignore = PathSpec.from_lines("gitwildmatch", [])
-        # `child` should behave like a symlink which resolved path is clearly
-        # outside of the `root` directory.
-        path.iterdir.return_value = [child]
-        child.resolve.return_value = Path("/a/b/c")
-        child.as_posix.return_value = "/a/b/c"
-        child.is_symlink.return_value = True
-        try:
-            list(
-                black.gen_python_files(
-                    path.iterdir(), root, include, exclude, report, gitignore
-                )
-            )
-        except ValueError as ve:
-            self.fail(f"`get_python_files_in_dir()` failed: {ve}")
-        path.iterdir.assert_called_once()
-        child.resolve.assert_called_once()
-        child.is_symlink.assert_called_once()
-        # `child` should behave like a strange file which resolved path is clearly
-        # outside of the `root` directory.
-        child.is_symlink.return_value = False
-        with self.assertRaises(ValueError):
-            list(
-                black.gen_python_files(
-                    path.iterdir(), root, include, exclude, report, gitignore
-                )
-            )
-        path.iterdir.assert_called()
-        self.assertEqual(path.iterdir.call_count, 2)
-        child.resolve.assert_called()
-        self.assertEqual(child.resolve.call_count, 2)
-        child.is_symlink.assert_called()
-        self.assertEqual(child.is_symlink.call_count, 2)
-

     def test_shhh_click(self) -> None:
         try:
     def test_shhh_click(self) -> None:
         try:

-            from click import _unicodefun  # type: ignore
+            from click import _unicodefun

         except ModuleNotFoundError:
             self.skipTest("Incompatible Click version")
         if not hasattr(_unicodefun, "_verify_python3_env"):
         except ModuleNotFoundError:
             self.skipTest("Incompatible Click version")
         if not hasattr(_unicodefun, "_verify_python3_env"):


@@ -1719,14 +1265,14 @@ class BlackTestCase(unittest.TestCase):
         with patch("locale.getpreferredencoding") as gpe:
             gpe.return_value = "ASCII"
             with self.assertRaises(RuntimeError):
         with patch("locale.getpreferredencoding") as gpe:
             gpe.return_value = "ASCII"
             with self.assertRaises(RuntimeError):

-                _unicodefun._verify_python3_env()
+                _unicodefun._verify_python3_env()  # type: ignore

         # Now, let's silence Click...
         black.patch_click()
         # ...and confirm it's silent.
         with patch("locale.getpreferredencoding") as gpe:
             gpe.return_value = "ASCII"
             try:
         # Now, let's silence Click...
         black.patch_click()
         # ...and confirm it's silent.
         with patch("locale.getpreferredencoding") as gpe:
             gpe.return_value = "ASCII"
             try:

-                _unicodefun._verify_python3_env()
+                _unicodefun._verify_python3_env()  # type: ignore

             except RuntimeError as re:
                 self.fail(f"`patch_click()` failed, exception still raised: {re}")
 
             except RuntimeError as re:
                 self.fail(f"`patch_click()` failed, exception still raised: {re}")
 


@@ -1743,15 +1289,7 @@ class BlackTestCase(unittest.TestCase):
             critical=fail,
             log=fail,
         ):
             critical=fail,
             log=fail,
         ):

-            ff(THIS_FILE)
-
-    @unittest.skipUnless(has_blackd_deps, "blackd's dependencies are not installed")
-    def test_blackd_main(self) -> None:
-        with patch("blackd.web.run_app"):
-            result = CliRunner().invoke(blackd.main, [])
-            if result.exception is not None:
-                raise result.exception
-            self.assertEqual(result.exit_code, 0)
+            ff(THIS_DIR / "util.py")

 
     def test_invalid_config_return_code(self) -> None:
         tmp_file = Path(black.dump_to_file())
 
     def test_invalid_config_return_code(self) -> None:
         tmp_file = Path(black.dump_to_file())


@@ -1772,25 +1310,14 @@ class BlackTestCase(unittest.TestCase):
         self.assertEqual(config["color"], True)
         self.assertEqual(config["line_length"], 79)
         self.assertEqual(config["target_version"], ["py36", "py37", "py38"])
         self.assertEqual(config["color"], True)
         self.assertEqual(config["line_length"], 79)
         self.assertEqual(config["target_version"], ["py36", "py37", "py38"])

+        self.assertEqual(config["python_cell_magics"], ["custom1", "custom2"])

         self.assertEqual(config["exclude"], r"\.pyi?$")
         self.assertEqual(config["include"], r"\.py?$")
 
     def test_read_pyproject_toml(self) -> None:
         test_toml_file = THIS_DIR / "test.toml"
         self.assertEqual(config["exclude"], r"\.pyi?$")
         self.assertEqual(config["include"], r"\.py?$")
 
     def test_read_pyproject_toml(self) -> None:
         test_toml_file = THIS_DIR / "test.toml"

-
-        # Fake a click context and parameter so mypy stays happy
-        class FakeContext(click.Context):
-            def __init__(self) -> None:
-                self.default_map: Dict[str, Any] = {}
-
-        class FakeParameter(click.Parameter):
-            def __init__(self) -> None:
-                pass
-

         fake_ctx = FakeContext()
         fake_ctx = FakeContext()

-        black.read_pyproject_toml(
-            fake_ctx, FakeParameter(), str(test_toml_file),
-        )
+        black.read_pyproject_toml(fake_ctx, FakeParameter(), str(test_toml_file))

         config = fake_ctx.default_map
         self.assertEqual(config["verbose"], "1")
         self.assertEqual(config["check"], "no")
         config = fake_ctx.default_map
         self.assertEqual(config["verbose"], "1")
         self.assertEqual(config["check"], "no")


@@ -1801,6 +1328,7 @@ class BlackTestCase(unittest.TestCase):
         self.assertEqual(config["exclude"], r"\.pyi?$")
         self.assertEqual(config["include"], r"\.py?$")
 
         self.assertEqual(config["exclude"], r"\.pyi?$")
         self.assertEqual(config["include"], r"\.py?$")
 

+    @pytest.mark.incompatible_with_mypyc

     def test_find_project_root(self) -> None:
         with TemporaryDirectory() as workspace:
             root = Path(workspace)
     def test_find_project_root(self) -> None:
         with TemporaryDirectory() as workspace:
             root = Path(workspace)


@@ -1818,179 +1346,784 @@ class BlackTestCase(unittest.TestCase):
             src_python.touch()
 
             self.assertEqual(
             src_python.touch()
 
             self.assertEqual(

-                black.find_project_root((src_dir, test_dir)), root.resolve()
+                black.find_project_root((src_dir, test_dir)),
+                (root.resolve(), "pyproject.toml"),
+            )
+            self.assertEqual(
+                black.find_project_root((src_dir,)),
+                (src_dir.resolve(), "pyproject.toml"),
+            )
+            self.assertEqual(
+                black.find_project_root((src_python,)),
+                (src_dir.resolve(), "pyproject.toml"),
+            )
+
+    @patch(
+        "black.files.find_user_pyproject_toml",
+    )
+    def test_find_pyproject_toml(self, find_user_pyproject_toml: MagicMock) -> None:
+        find_user_pyproject_toml.side_effect = RuntimeError()
+
+        with redirect_stderr(io.StringIO()) as stderr:
+            result = black.files.find_pyproject_toml(
+                path_search_start=(str(Path.cwd().root),)

             )
             )

-            self.assertEqual(black.find_project_root((src_dir,)), src_dir.resolve())
-            self.assertEqual(black.find_project_root((src_python,)), src_dir.resolve())
-
-
-class BlackDTestCase(AioHTTPTestCase):
-    async def get_application(self) -> web.Application:
-        return blackd.make_app()
-
-    # TODO: remove these decorators once the below is released
-    # https://github.com/aio-libs/aiohttp/pull/3727
-    @skip_if_exception("ClientOSError")
-    @unittest.skipUnless(has_blackd_deps, "blackd's dependencies are not installed")
-    @unittest_run_loop
-    async def test_blackd_request_needs_formatting(self) -> None:
-        response = await self.client.post("/", data=b"print('hello world')")
-        self.assertEqual(response.status, 200)
-        self.assertEqual(response.charset, "utf8")
-        self.assertEqual(await response.read(), b'print("hello world")\n')
-
-    @skip_if_exception("ClientOSError")
-    @unittest.skipUnless(has_blackd_deps, "blackd's dependencies are not installed")
-    @unittest_run_loop
-    async def test_blackd_request_no_change(self) -> None:
-        response = await self.client.post("/", data=b'print("hello world")\n')
-        self.assertEqual(response.status, 204)
-        self.assertEqual(await response.read(), b"")
-
-    @skip_if_exception("ClientOSError")
-    @unittest.skipUnless(has_blackd_deps, "blackd's dependencies are not installed")
-    @unittest_run_loop
-    async def test_blackd_request_syntax_error(self) -> None:
-        response = await self.client.post("/", data=b"what even ( is")
-        self.assertEqual(response.status, 400)
-        content = await response.text()
-        self.assertTrue(
-            content.startswith("Cannot parse"),
-            msg=f"Expected error to start with 'Cannot parse', got {repr(content)}",
+
+        assert result is None
+        err = stderr.getvalue()
+        assert "Ignoring user configuration" in err
+
+    @patch(
+        "black.files.find_user_pyproject_toml",
+        black.files.find_user_pyproject_toml.__wrapped__,
+    )
+    def test_find_user_pyproject_toml_linux(self) -> None:
+        if system() == "Windows":
+            return
+
+        # Test if XDG_CONFIG_HOME is checked
+        with TemporaryDirectory() as workspace:
+            tmp_user_config = Path(workspace) / "black"
+            with patch.dict("os.environ", {"XDG_CONFIG_HOME": workspace}):
+                self.assertEqual(
+                    black.files.find_user_pyproject_toml(), tmp_user_config.resolve()
+                )
+
+        # Test fallback for XDG_CONFIG_HOME
+        with patch.dict("os.environ"):
+            os.environ.pop("XDG_CONFIG_HOME", None)
+            fallback_user_config = Path("~/.config").expanduser() / "black"
+            self.assertEqual(
+                black.files.find_user_pyproject_toml(), fallback_user_config.resolve()
+            )
+
+    def test_find_user_pyproject_toml_windows(self) -> None:
+        if system() != "Windows":
+            return
+
+        user_config_path = Path.home() / ".black"
+        self.assertEqual(
+            black.files.find_user_pyproject_toml(), user_config_path.resolve()

         )
 
         )
 

-    @skip_if_exception("ClientOSError")
-    @unittest.skipUnless(has_blackd_deps, "blackd's dependencies are not installed")
-    @unittest_run_loop
-    async def test_blackd_unsupported_version(self) -> None:
-        response = await self.client.post(
-            "/", data=b"what", headers={blackd.PROTOCOL_VERSION_HEADER: "2"}
+    def test_bpo_33660_workaround(self) -> None:
+        if system() == "Windows":
+            return
+
+        # https://bugs.python.org/issue33660
+        root = Path("/")
+        with change_directory(root):
+            path = Path("workspace") / "project"
+            report = black.Report(verbose=True)
+            normalized_path = black.normalize_path_maybe_ignore(path, root, report)
+            self.assertEqual(normalized_path, "workspace/project")
+
+    def test_normalize_path_ignore_windows_junctions_outside_of_root(self) -> None:
+        if system() != "Windows":
+            return
+
+        with TemporaryDirectory() as workspace:
+            root = Path(workspace)
+            junction_dir = root / "junction"
+            junction_target_outside_of_root = root / ".."
+            os.system(f"mklink /J {junction_dir} {junction_target_outside_of_root}")
+
+            report = black.Report(verbose=True)
+            normalized_path = black.normalize_path_maybe_ignore(
+                junction_dir, root, report
+            )
+            # Manually delete for Python < 3.8
+            os.system(f"rmdir {junction_dir}")
+
+            self.assertEqual(normalized_path, None)
+
+    def test_newline_comment_interaction(self) -> None:
+        source = "class A:\\\r\n# type: ignore\n pass\n"
+        output = black.format_str(source, mode=DEFAULT_MODE)
+        black.assert_stable(source, output, mode=DEFAULT_MODE)
+
+    def test_bpo_2142_workaround(self) -> None:
+
+        # https://bugs.python.org/issue2142
+
+        source, _ = read_data("missing_final_newline.py")
+        # read_data adds a trailing newline
+        source = source.rstrip()
+        expected, _ = read_data("missing_final_newline.diff")
+        tmp_file = Path(black.dump_to_file(source, ensure_final_newline=False))
+        diff_header = re.compile(
+            rf"{re.escape(str(tmp_file))}\t\d\d\d\d-\d\d-\d\d "
+            r"\d\d:\d\d:\d\d\.\d\d\d\d\d\d \+\d\d\d\d"

         )
         )

-        self.assertEqual(response.status, 501)
-
-    @skip_if_exception("ClientOSError")
-    @unittest.skipUnless(has_blackd_deps, "blackd's dependencies are not installed")
-    @unittest_run_loop
-    async def test_blackd_supported_version(self) -> None:
-        response = await self.client.post(
-            "/", data=b"what", headers={blackd.PROTOCOL_VERSION_HEADER: "1"}
+        try:
+            result = BlackRunner().invoke(black.main, ["--diff", str(tmp_file)])
+            self.assertEqual(result.exit_code, 0)
+        finally:
+            os.unlink(tmp_file)
+        actual = result.output
+        actual = diff_header.sub(DETERMINISTIC_HEADER, actual)
+        self.assertEqual(actual, expected)
+
+    @staticmethod
+    def compare_results(
+        result: click.testing.Result, expected_value: str, expected_exit_code: int
+    ) -> None:
+        """Helper method to test the value and exit code of a click Result."""
+        assert (
+            result.output == expected_value
+        ), "The output did not match the expected value."
+        assert result.exit_code == expected_exit_code, "The exit code is incorrect."
+
+    def test_code_option(self) -> None:
+        """Test the code option with no changes."""
+        code = 'print("Hello world")\n'
+        args = ["--code", code]
+        result = CliRunner().invoke(black.main, args)
+
+        self.compare_results(result, code, 0)
+
+    def test_code_option_changed(self) -> None:
+        """Test the code option when changes are required."""
+        code = "print('hello world')"
+        formatted = black.format_str(code, mode=DEFAULT_MODE)
+
+        args = ["--code", code]
+        result = CliRunner().invoke(black.main, args)
+
+        self.compare_results(result, formatted, 0)
+
+    def test_code_option_check(self) -> None:
+        """Test the code option when check is passed."""
+        args = ["--check", "--code", 'print("Hello world")\n']
+        result = CliRunner().invoke(black.main, args)
+        self.compare_results(result, "", 0)
+
+    def test_code_option_check_changed(self) -> None:
+        """Test the code option when changes are required, and check is passed."""
+        args = ["--check", "--code", "print('hello world')"]
+        result = CliRunner().invoke(black.main, args)
+        self.compare_results(result, "", 1)
+
+    def test_code_option_diff(self) -> None:
+        """Test the code option when diff is passed."""
+        code = "print('hello world')"
+        formatted = black.format_str(code, mode=DEFAULT_MODE)
+        result_diff = diff(code, formatted, "STDIN", "STDOUT")
+
+        args = ["--diff", "--code", code]
+        result = CliRunner().invoke(black.main, args)
+
+        # Remove time from diff
+        output = DIFF_TIME.sub("", result.output)
+
+        assert output == result_diff, "The output did not match the expected value."
+        assert result.exit_code == 0, "The exit code is incorrect."
+
+    def test_code_option_color_diff(self) -> None:
+        """Test the code option when color and diff are passed."""
+        code = "print('hello world')"
+        formatted = black.format_str(code, mode=DEFAULT_MODE)
+
+        result_diff = diff(code, formatted, "STDIN", "STDOUT")
+        result_diff = color_diff(result_diff)
+
+        args = ["--diff", "--color", "--code", code]
+        result = CliRunner().invoke(black.main, args)
+
+        # Remove time from diff
+        output = DIFF_TIME.sub("", result.output)
+
+        assert output == result_diff, "The output did not match the expected value."
+        assert result.exit_code == 0, "The exit code is incorrect."
+
+    @pytest.mark.incompatible_with_mypyc
+    def test_code_option_safe(self) -> None:
+        """Test that the code option throws an error when the sanity checks fail."""
+        # Patch black.assert_equivalent to ensure the sanity checks fail
+        with patch.object(black, "assert_equivalent", side_effect=AssertionError):
+            code = 'print("Hello world")'
+            error_msg = f"{code}\nerror: cannot format <string>: \n"
+
+            args = ["--safe", "--code", code]
+            result = CliRunner().invoke(black.main, args)
+
+            self.compare_results(result, error_msg, 123)
+
+    def test_code_option_fast(self) -> None:
+        """Test that the code option ignores errors when the sanity checks fail."""
+        # Patch black.assert_equivalent to ensure the sanity checks fail
+        with patch.object(black, "assert_equivalent", side_effect=AssertionError):
+            code = 'print("Hello world")'
+            formatted = black.format_str(code, mode=DEFAULT_MODE)
+
+            args = ["--fast", "--code", code]
+            result = CliRunner().invoke(black.main, args)
+
+            self.compare_results(result, formatted, 0)
+
+    @pytest.mark.incompatible_with_mypyc
+    def test_code_option_config(self) -> None:
+        """
+        Test that the code option finds the pyproject.toml in the current directory.
+        """
+        with patch.object(black, "parse_pyproject_toml", return_value={}) as parse:
+            args = ["--code", "print"]
+            # This is the only directory known to contain a pyproject.toml
+            with change_directory(PROJECT_ROOT):
+                CliRunner().invoke(black.main, args)
+                pyproject_path = Path(Path.cwd(), "pyproject.toml").resolve()
+
+            assert (
+                len(parse.mock_calls) >= 1
+            ), "Expected config parse to be called with the current directory."
+
+            _, call_args, _ = parse.mock_calls[0]
+            assert (
+                call_args[0].lower() == str(pyproject_path).lower()
+            ), "Incorrect config loaded."
+
+    @pytest.mark.incompatible_with_mypyc
+    def test_code_option_parent_config(self) -> None:
+        """
+        Test that the code option finds the pyproject.toml in the parent directory.
+        """
+        with patch.object(black, "parse_pyproject_toml", return_value={}) as parse:
+            with change_directory(THIS_DIR):
+                args = ["--code", "print"]
+                CliRunner().invoke(black.main, args)
+
+                pyproject_path = Path(Path().cwd().parent, "pyproject.toml").resolve()
+                assert (
+                    len(parse.mock_calls) >= 1
+                ), "Expected config parse to be called with the current directory."
+
+                _, call_args, _ = parse.mock_calls[0]
+                assert (
+                    call_args[0].lower() == str(pyproject_path).lower()
+                ), "Incorrect config loaded."
+
+    def test_for_handled_unexpected_eof_error(self) -> None:
+        """
+        Test that an unexpected EOF SyntaxError is nicely presented.
+        """
+        with pytest.raises(black.parsing.InvalidInput) as exc_info:
+            black.lib2to3_parse("print(", {})
+
+        exc_info.match("Cannot parse: 2:0: EOF in multi-line statement")
+
+    def test_equivalency_ast_parse_failure_includes_error(self) -> None:
+        with pytest.raises(AssertionError) as err:
+            black.assert_equivalent("a«»a  = 1", "a«»a  = 1")
+
+        err.match("--safe")
+        # Unfortunately the SyntaxError message has changed in newer versions so we
+        # can't match it directly.
+        err.match("invalid character")
+        err.match(r"\(<unknown>, line 1\)")
+
+
+class TestCaching:
+    def test_get_cache_dir(
+        self,
+        tmp_path: Path,
+        monkeypatch: pytest.MonkeyPatch,
+    ) -> None:
+        # Create multiple cache directories
+        workspace1 = tmp_path / "ws1"
+        workspace1.mkdir()
+        workspace2 = tmp_path / "ws2"
+        workspace2.mkdir()
+
+        # Force user_cache_dir to use the temporary directory for easier assertions
+        patch_user_cache_dir = patch(
+            target="black.cache.user_cache_dir",
+            autospec=True,
+            return_value=str(workspace1),

         )
         )

-        self.assertEqual(response.status, 200)
-
-    @skip_if_exception("ClientOSError")
-    @unittest.skipUnless(has_blackd_deps, "blackd's dependencies are not installed")
-    @unittest_run_loop
-    async def test_blackd_invalid_python_variant(self) -> None:
-        async def check(header_value: str, expected_status: int = 400) -> None:
-            response = await self.client.post(
-                "/", data=b"what", headers={blackd.PYTHON_VARIANT_HEADER: header_value}
+
+        # If BLACK_CACHE_DIR is not set, use user_cache_dir
+        monkeypatch.delenv("BLACK_CACHE_DIR", raising=False)
+        with patch_user_cache_dir:
+            assert get_cache_dir() == workspace1
+
+        # If it is set, use the path provided in the env var.
+        monkeypatch.setenv("BLACK_CACHE_DIR", str(workspace2))
+        assert get_cache_dir() == workspace2
+
+    def test_cache_broken_file(self) -> None:
+        mode = DEFAULT_MODE
+        with cache_dir() as workspace:
+            cache_file = get_cache_file(mode)
+            cache_file.write_text("this is not a pickle")
+            assert black.read_cache(mode) == {}
+            src = (workspace / "test.py").resolve()
+            src.write_text("print('hello')")
+            invokeBlack([str(src)])
+            cache = black.read_cache(mode)
+            assert str(src) in cache
+
+    def test_cache_single_file_already_cached(self) -> None:
+        mode = DEFAULT_MODE
+        with cache_dir() as workspace:
+            src = (workspace / "test.py").resolve()
+            src.write_text("print('hello')")
+            black.write_cache({}, [src], mode)
+            invokeBlack([str(src)])
+            assert src.read_text() == "print('hello')"
+
+    @event_loop()
+    def test_cache_multiple_files(self) -> None:
+        mode = DEFAULT_MODE
+        with cache_dir() as workspace, patch(
+            "black.ProcessPoolExecutor", new=ThreadPoolExecutor
+        ):
+            one = (workspace / "one.py").resolve()
+            with one.open("w") as fobj:
+                fobj.write("print('hello')")
+            two = (workspace / "two.py").resolve()
+            with two.open("w") as fobj:
+                fobj.write("print('hello')")
+            black.write_cache({}, [one], mode)
+            invokeBlack([str(workspace)])
+            with one.open("r") as fobj:
+                assert fobj.read() == "print('hello')"
+            with two.open("r") as fobj:
+                assert fobj.read() == 'print("hello")\n'
+            cache = black.read_cache(mode)
+            assert str(one) in cache
+            assert str(two) in cache
+
+    @pytest.mark.parametrize("color", [False, True], ids=["no-color", "with-color"])
+    def test_no_cache_when_writeback_diff(self, color: bool) -> None:
+        mode = DEFAULT_MODE
+        with cache_dir() as workspace:
+            src = (workspace / "test.py").resolve()
+            with src.open("w") as fobj:
+                fobj.write("print('hello')")
+            with patch("black.read_cache") as read_cache, patch(
+                "black.write_cache"
+            ) as write_cache:
+                cmd = [str(src), "--diff"]
+                if color:
+                    cmd.append("--color")
+                invokeBlack(cmd)
+                cache_file = get_cache_file(mode)
+                assert cache_file.exists() is False
+                write_cache.assert_not_called()
+                read_cache.assert_not_called()
+
+    @pytest.mark.parametrize("color", [False, True], ids=["no-color", "with-color"])
+    @event_loop()
+    def test_output_locking_when_writeback_diff(self, color: bool) -> None:
+        with cache_dir() as workspace:
+            for tag in range(0, 4):
+                src = (workspace / f"test{tag}.py").resolve()
+                with src.open("w") as fobj:
+                    fobj.write("print('hello')")
+            with patch("black.Manager", wraps=multiprocessing.Manager) as mgr:
+                cmd = ["--diff", str(workspace)]
+                if color:
+                    cmd.append("--color")
+                invokeBlack(cmd, exit_code=0)
+                # this isn't quite doing what we want, but if it _isn't_
+                # called then we cannot be using the lock it provides
+                mgr.assert_called()
+
+    def test_no_cache_when_stdin(self) -> None:
+        mode = DEFAULT_MODE
+        with cache_dir():
+            result = CliRunner().invoke(
+                black.main, ["-"], input=BytesIO(b"print('hello')")
+            )
+            assert not result.exit_code
+            cache_file = get_cache_file(mode)
+            assert not cache_file.exists()
+
+    def test_read_cache_no_cachefile(self) -> None:
+        mode = DEFAULT_MODE
+        with cache_dir():
+            assert black.read_cache(mode) == {}
+
+    def test_write_cache_read_cache(self) -> None:
+        mode = DEFAULT_MODE
+        with cache_dir() as workspace:
+            src = (workspace / "test.py").resolve()
+            src.touch()
+            black.write_cache({}, [src], mode)
+            cache = black.read_cache(mode)
+            assert str(src) in cache
+            assert cache[str(src)] == black.get_cache_info(src)
+
+    def test_filter_cached(self) -> None:
+        with TemporaryDirectory() as workspace:
+            path = Path(workspace)
+            uncached = (path / "uncached").resolve()
+            cached = (path / "cached").resolve()
+            cached_but_changed = (path / "changed").resolve()
+            uncached.touch()
+            cached.touch()
+            cached_but_changed.touch()
+            cache = {
+                str(cached): black.get_cache_info(cached),
+                str(cached_but_changed): (0.0, 0),
+            }
+            todo, done = black.filter_cached(
+                cache, {uncached, cached, cached_but_changed}

             )
             )

-            self.assertEqual(response.status, expected_status)
-
-        await check("lol")
-        await check("ruby3.5")
-        await check("pyi3.6")
-        await check("py1.5")
-        await check("2.8")
-        await check("py2.8")
-        await check("3.0")
-        await check("pypy3.0")
-        await check("jython3.4")
-
-    @skip_if_exception("ClientOSError")
-    @unittest.skipUnless(has_blackd_deps, "blackd's dependencies are not installed")
-    @unittest_run_loop
-    async def test_blackd_pyi(self) -> None:
-        source, expected = read_data("stub.pyi")
-        response = await self.client.post(
-            "/", data=source, headers={blackd.PYTHON_VARIANT_HEADER: "pyi"}
+            assert todo == {uncached, cached_but_changed}
+            assert done == {cached}
+
+    def test_write_cache_creates_directory_if_needed(self) -> None:
+        mode = DEFAULT_MODE
+        with cache_dir(exists=False) as workspace:
+            assert not workspace.exists()
+            black.write_cache({}, [], mode)
+            assert workspace.exists()
+
+    @event_loop()
+    def test_failed_formatting_does_not_get_cached(self) -> None:
+        mode = DEFAULT_MODE
+        with cache_dir() as workspace, patch(
+            "black.ProcessPoolExecutor", new=ThreadPoolExecutor
+        ):
+            failing = (workspace / "failing.py").resolve()
+            with failing.open("w") as fobj:
+                fobj.write("not actually python")
+            clean = (workspace / "clean.py").resolve()
+            with clean.open("w") as fobj:
+                fobj.write('print("hello")\n')
+            invokeBlack([str(workspace)], exit_code=123)
+            cache = black.read_cache(mode)
+            assert str(failing) not in cache
+            assert str(clean) in cache
+
+    def test_write_cache_write_fail(self) -> None:
+        mode = DEFAULT_MODE
+        with cache_dir(), patch.object(Path, "open") as mock:
+            mock.side_effect = OSError
+            black.write_cache({}, [], mode)
+
+    def test_read_cache_line_lengths(self) -> None:
+        mode = DEFAULT_MODE
+        short_mode = replace(DEFAULT_MODE, line_length=1)
+        with cache_dir() as workspace:
+            path = (workspace / "file.py").resolve()
+            path.touch()
+            black.write_cache({}, [path], mode)
+            one = black.read_cache(mode)
+            assert str(path) in one
+            two = black.read_cache(short_mode)
+            assert str(path) not in two
+
+
+def assert_collected_sources(
+    src: Sequence[Union[str, Path]],
+    expected: Sequence[Union[str, Path]],
+    *,
+    ctx: Optional[FakeContext] = None,
+    exclude: Optional[str] = None,
+    include: Optional[str] = None,
+    extend_exclude: Optional[str] = None,
+    force_exclude: Optional[str] = None,
+    stdin_filename: Optional[str] = None,
+) -> None:
+    gs_src = tuple(str(Path(s)) for s in src)
+    gs_expected = [Path(s) for s in expected]
+    gs_exclude = None if exclude is None else compile_pattern(exclude)
+    gs_include = DEFAULT_INCLUDE if include is None else compile_pattern(include)
+    gs_extend_exclude = (
+        None if extend_exclude is None else compile_pattern(extend_exclude)
+    )
+    gs_force_exclude = None if force_exclude is None else compile_pattern(force_exclude)
+    collected = black.get_sources(
+        ctx=ctx or FakeContext(),
+        src=gs_src,
+        quiet=False,
+        verbose=False,
+        include=gs_include,
+        exclude=gs_exclude,
+        extend_exclude=gs_extend_exclude,
+        force_exclude=gs_force_exclude,
+        report=black.Report(),
+        stdin_filename=stdin_filename,
+    )
+    assert sorted(collected) == sorted(gs_expected)
+
+
+class TestFileCollection:
+    def test_include_exclude(self) -> None:
+        path = THIS_DIR / "data" / "include_exclude_tests"
+        src = [path]
+        expected = [
+            Path(path / "b/dont_exclude/a.py"),
+            Path(path / "b/dont_exclude/a.pyi"),
+        ]
+        assert_collected_sources(
+            src,
+            expected,
+            include=r"\.pyi?$",
+            exclude=r"/exclude/|/\.definitely_exclude/",

         )
         )

-        self.assertEqual(response.status, 200)
-        self.assertEqual(await response.text(), expected)

 
 

-    @skip_if_exception("ClientOSError")
-    @unittest.skipUnless(has_blackd_deps, "blackd's dependencies are not installed")
-    @unittest_run_loop
-    async def test_blackd_diff(self) -> None:
-        diff_header = re.compile(
-            r"(In|Out)\t\d\d\d\d-\d\d-\d\d \d\d:\d\d:\d\d\.\d\d\d\d\d\d \+\d\d\d\d"
+    def test_gitignore_used_as_default(self) -> None:
+        base = Path(DATA_DIR / "include_exclude_tests")
+        expected = [
+            base / "b/.definitely_exclude/a.py",
+            base / "b/.definitely_exclude/a.pyi",
+        ]
+        src = [base / "b/"]
+        ctx = FakeContext()
+        ctx.obj["root"] = base
+        assert_collected_sources(src, expected, ctx=ctx, extend_exclude=r"/exclude/")
+
+    @patch("black.find_project_root", lambda *args: (THIS_DIR.resolve(), None))
+    def test_exclude_for_issue_1572(self) -> None:
+        # Exclude shouldn't touch files that were explicitly given to Black through the
+        # CLI. Exclude is supposed to only apply to the recursive discovery of files.
+        # https://github.com/psf/black/issues/1572
+        path = DATA_DIR / "include_exclude_tests"
+        src = [path / "b/exclude/a.py"]
+        expected = [path / "b/exclude/a.py"]
+        assert_collected_sources(src, expected, include="", exclude=r"/exclude/|a\.py")
+
+    def test_gitignore_exclude(self) -> None:
+        path = THIS_DIR / "data" / "include_exclude_tests"
+        include = re.compile(r"\.pyi?$")
+        exclude = re.compile(r"")
+        report = black.Report()
+        gitignore = PathSpec.from_lines(
+            "gitwildmatch", ["exclude/", ".definitely_exclude"]
+        )
+        sources: List[Path] = []
+        expected = [
+            Path(path / "b/dont_exclude/a.py"),
+            Path(path / "b/dont_exclude/a.pyi"),
+        ]
+        this_abs = THIS_DIR.resolve()
+        sources.extend(
+            black.gen_python_files(
+                path.iterdir(),
+                this_abs,
+                include,
+                exclude,
+                None,
+                None,
+                report,
+                gitignore,
+                verbose=False,
+                quiet=False,
+            )

         )
         )

+        assert sorted(expected) == sorted(sources)

 
 

-        source, _ = read_data("blackd_diff.py")
-        expected, _ = read_data("blackd_diff.diff")
+    def test_nested_gitignore(self) -> None:
+        path = Path(THIS_DIR / "data" / "nested_gitignore_tests")
+        include = re.compile(r"\.pyi?$")
+        exclude = re.compile(r"")
+        root_gitignore = black.files.get_gitignore(path)
+        report = black.Report()
+        expected: List[Path] = [
+            Path(path / "x.py"),
+            Path(path / "root/b.py"),
+            Path(path / "root/c.py"),
+            Path(path / "root/child/c.py"),
+        ]
+        this_abs = THIS_DIR.resolve()
+        sources = list(
+            black.gen_python_files(
+                path.iterdir(),
+                this_abs,
+                include,
+                exclude,
+                None,
+                None,
+                report,
+                root_gitignore,
+                verbose=False,
+                quiet=False,
+            )
+        )
+        assert sorted(expected) == sorted(sources)

 
 

-        response = await self.client.post(
-            "/", data=source, headers={blackd.DIFF_HEADER: "true"}
+    def test_invalid_gitignore(self) -> None:
+        path = THIS_DIR / "data" / "invalid_gitignore_tests"
+        empty_config = path / "pyproject.toml"
+        result = BlackRunner().invoke(
+            black.main, ["--verbose", "--config", str(empty_config), str(path)]

         )
         )

-        self.assertEqual(response.status, 200)
+        assert result.exit_code == 1
+        assert result.stderr_bytes is not None

 
 

-        actual = await response.text()
-        actual = diff_header.sub(DETERMINISTIC_HEADER, actual)
-        self.assertEqual(actual, expected)
+        gitignore = path / ".gitignore"
+        assert f"Could not parse {gitignore}" in result.stderr_bytes.decode()

 
 

-    @skip_if_exception("ClientOSError")
-    @unittest.skipUnless(has_blackd_deps, "blackd's dependencies are not installed")
-    @unittest_run_loop
-    async def test_blackd_python_variant(self) -> None:
-        code = (
-            "def f(\n"
-            "    and_has_a_bunch_of,\n"
-            "    very_long_arguments_too,\n"
-            "    and_lots_of_them_as_well_lol,\n"
-            "    **and_very_long_keyword_arguments\n"
-            "):\n"
-            "    pass\n"
+    def test_invalid_nested_gitignore(self) -> None:
+        path = THIS_DIR / "data" / "invalid_nested_gitignore_tests"
+        empty_config = path / "pyproject.toml"
+        result = BlackRunner().invoke(
+            black.main, ["--verbose", "--config", str(empty_config), str(path)]

         )
         )

+        assert result.exit_code == 1
+        assert result.stderr_bytes is not None

 
 

-        async def check(header_value: str, expected_status: int) -> None:
-            response = await self.client.post(
-                "/", data=code, headers={blackd.PYTHON_VARIANT_HEADER: header_value}
-            )
-            self.assertEqual(
-                response.status, expected_status, msg=await response.text()
+        gitignore = path / "a" / ".gitignore"
+        assert f"Could not parse {gitignore}" in result.stderr_bytes.decode()
+
+    def test_empty_include(self) -> None:
+        path = DATA_DIR / "include_exclude_tests"
+        src = [path]
+        expected = [
+            Path(path / "b/exclude/a.pie"),
+            Path(path / "b/exclude/a.py"),
+            Path(path / "b/exclude/a.pyi"),
+            Path(path / "b/dont_exclude/a.pie"),
+            Path(path / "b/dont_exclude/a.py"),
+            Path(path / "b/dont_exclude/a.pyi"),
+            Path(path / "b/.definitely_exclude/a.pie"),
+            Path(path / "b/.definitely_exclude/a.py"),
+            Path(path / "b/.definitely_exclude/a.pyi"),
+            Path(path / ".gitignore"),
+            Path(path / "pyproject.toml"),
+        ]
+        # Setting exclude explicitly to an empty string to block .gitignore usage.
+        assert_collected_sources(src, expected, include="", exclude="")
+
+    def test_extend_exclude(self) -> None:
+        path = DATA_DIR / "include_exclude_tests"
+        src = [path]
+        expected = [
+            Path(path / "b/exclude/a.py"),
+            Path(path / "b/dont_exclude/a.py"),
+        ]
+        assert_collected_sources(
+            src, expected, exclude=r"\.pyi$", extend_exclude=r"\.definitely_exclude"
+        )
+
+    @pytest.mark.incompatible_with_mypyc
+    def test_symlink_out_of_root_directory(self) -> None:
+        path = MagicMock()
+        root = THIS_DIR.resolve()
+        child = MagicMock()
+        include = re.compile(black.DEFAULT_INCLUDES)
+        exclude = re.compile(black.DEFAULT_EXCLUDES)
+        report = black.Report()
+        gitignore = PathSpec.from_lines("gitwildmatch", [])
+        # `child` should behave like a symlink which resolved path is clearly
+        # outside of the `root` directory.
+        path.iterdir.return_value = [child]
+        child.resolve.return_value = Path("/a/b/c")
+        child.as_posix.return_value = "/a/b/c"
+        try:
+            list(
+                black.gen_python_files(
+                    path.iterdir(),
+                    root,
+                    include,
+                    exclude,
+                    None,
+                    None,
+                    report,
+                    gitignore,
+                    verbose=False,
+                    quiet=False,
+                )

             )
             )

+        except ValueError as ve:
+            pytest.fail(f"`get_python_files_in_dir()` failed: {ve}")
+        path.iterdir.assert_called_once()
+        child.resolve.assert_called_once()

 
 

-        await check("3.6", 200)
-        await check("py3.6", 200)
-        await check("3.6,3.7", 200)
-        await check("3.6,py3.7", 200)
-        await check("py36,py37", 200)
-        await check("36", 200)
-        await check("3.6.4", 200)
-
-        await check("2", 204)
-        await check("2.7", 204)
-        await check("py2.7", 204)
-        await check("3.4", 204)
-        await check("py3.4", 204)
-        await check("py34,py36", 204)
-        await check("34", 204)
-
-    @skip_if_exception("ClientOSError")
-    @unittest.skipUnless(has_blackd_deps, "blackd's dependencies are not installed")
-    @unittest_run_loop
-    async def test_blackd_line_length(self) -> None:
-        response = await self.client.post(
-            "/", data=b'print("hello")\n', headers={blackd.LINE_LENGTH_HEADER: "7"}
+    @patch("black.find_project_root", lambda *args: (THIS_DIR.resolve(), None))
+    def test_get_sources_with_stdin(self) -> None:
+        src = ["-"]
+        expected = ["-"]
+        assert_collected_sources(src, expected, include="", exclude=r"/exclude/|a\.py")
+
+    @patch("black.find_project_root", lambda *args: (THIS_DIR.resolve(), None))
+    def test_get_sources_with_stdin_filename(self) -> None:
+        src = ["-"]
+        stdin_filename = str(THIS_DIR / "data/collections.py")
+        expected = [f"__BLACK_STDIN_FILENAME__{stdin_filename}"]
+        assert_collected_sources(
+            src,
+            expected,
+            exclude=r"/exclude/a\.py",
+            stdin_filename=stdin_filename,

         )
         )

-        self.assertEqual(response.status, 200)
-
-    @skip_if_exception("ClientOSError")
-    @unittest.skipUnless(has_blackd_deps, "blackd's dependencies are not installed")
-    @unittest_run_loop
-    async def test_blackd_invalid_line_length(self) -> None:
-        response = await self.client.post(
-            "/", data=b'print("hello")\n', headers={blackd.LINE_LENGTH_HEADER: "NaN"}
+
+    @patch("black.find_project_root", lambda *args: (THIS_DIR.resolve(), None))
+    def test_get_sources_with_stdin_filename_and_exclude(self) -> None:
+        # Exclude shouldn't exclude stdin_filename since it is mimicking the
+        # file being passed directly. This is the same as
+        # test_exclude_for_issue_1572
+        path = DATA_DIR / "include_exclude_tests"
+        src = ["-"]
+        stdin_filename = str(path / "b/exclude/a.py")
+        expected = [f"__BLACK_STDIN_FILENAME__{stdin_filename}"]
+        assert_collected_sources(
+            src,
+            expected,
+            exclude=r"/exclude/|a\.py",
+            stdin_filename=stdin_filename,

         )
         )

-        self.assertEqual(response.status, 400)

 
 

-    @skip_if_exception("ClientOSError")
-    @unittest.skipUnless(has_blackd_deps, "blackd's dependencies are not installed")
-    @unittest_run_loop
-    async def test_blackd_response_black_version_header(self) -> None:
-        response = await self.client.post("/")
-        self.assertIsNotNone(response.headers.get(blackd.BLACK_VERSION_HEADER))
+    @patch("black.find_project_root", lambda *args: (THIS_DIR.resolve(), None))
+    def test_get_sources_with_stdin_filename_and_extend_exclude(self) -> None:
+        # Extend exclude shouldn't exclude stdin_filename since it is mimicking the
+        # file being passed directly. This is the same as
+        # test_exclude_for_issue_1572
+        src = ["-"]
+        path = THIS_DIR / "data" / "include_exclude_tests"
+        stdin_filename = str(path / "b/exclude/a.py")
+        expected = [f"__BLACK_STDIN_FILENAME__{stdin_filename}"]
+        assert_collected_sources(
+            src,
+            expected,
+            extend_exclude=r"/exclude/|a\.py",
+            stdin_filename=stdin_filename,
+        )
+
+    @patch("black.find_project_root", lambda *args: (THIS_DIR.resolve(), None))
+    def test_get_sources_with_stdin_filename_and_force_exclude(self) -> None:
+        # Force exclude should exclude the file when passing it through
+        # stdin_filename
+        path = THIS_DIR / "data" / "include_exclude_tests"
+        stdin_filename = str(path / "b/exclude/a.py")
+        assert_collected_sources(
+            src=["-"],
+            expected=[],
+            force_exclude=r"/exclude/|a\.py",
+            stdin_filename=stdin_filename,
+        )

 
 
 
 

-if __name__ == "__main__":
-    unittest.main(module="test_black")
+try:
+    with open(black.__file__, "r", encoding="utf-8") as _bf:
+        black_source_lines = _bf.readlines()
+except UnicodeDecodeError:
+    if not black.COMPILED:
+        raise
+
+
+def tracefunc(
+    frame: types.FrameType, event: str, arg: Any
+) -> Callable[[types.FrameType, str, Any], Any]:
+    """Show function calls `from black/__init__.py` as they happen.
+
+    Register this with `sys.settrace()` in a test you're debugging.
+    """
+    if event != "call":
+        return tracefunc
+
+    stack = len(inspect.stack()) - 19
+    stack *= 2
+    filename = frame.f_code.co_filename
+    lineno = frame.f_lineno
+    func_sig_lineno = lineno - 1
+    funcname = black_source_lines[func_sig_lineno].strip()
+    while funcname.startswith("@"):
+        func_sig_lineno += 1
+        funcname = black_source_lines[func_sig_lineno].strip()
+    if "black/__init__.py" in filename:
+        print(f"{' ' * stack}{lineno}:{funcname}")
+    return tracefunc