Print out line diff on test failure (#2552)

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

diff --git a/tests/util.py b/tests/util.py
index ad9866975acfdffcd3407dcba7e9209b94918021..8755111f7c57716c76a8394711e2608cb621490b 100644 (file)
--- a/tests/util.py
+++ b/tests/util.py
@@ -1,66 +1,100 @@
 import os
+import sys
 import unittest
 from contextlib import contextmanager
+from functools import partial
 from pathlib import Path
-from typing import List, Tuple, Iterator, Any
+from typing import Any, Iterator, List, Optional, Tuple
+
 import black
-from functools import partial
+from black.debug import DebugVisitor
+from black.mode import TargetVersion
+from black.output import diff, err, out
 
 THIS_DIR = Path(__file__).parent
+DATA_DIR = THIS_DIR / "data"
 PROJECT_ROOT = THIS_DIR.parent
 EMPTY_LINE = "# EMPTY LINE WITH WHITESPACE" + " (this comment will be removed)"
 DETERMINISTIC_HEADER = "[Deterministic header]"
 
+PY36_VERSIONS = {
+    TargetVersion.PY36,
+    TargetVersion.PY37,
+    TargetVersion.PY38,
+    TargetVersion.PY39,
+}
 
 DEFAULT_MODE = black.Mode()
 ff = partial(black.format_file_in_place, mode=DEFAULT_MODE, fast=True)
 fs = partial(black.format_str, mode=DEFAULT_MODE)
 
 
+def _assert_format_equal(expected: str, actual: str) -> None:
+    if actual != expected and not os.environ.get("SKIP_AST_PRINT"):
+        bdv: DebugVisitor[Any]
+        out("Expected tree:", fg="green")
+        try:
+            exp_node = black.lib2to3_parse(expected)
+            bdv = DebugVisitor()
+            list(bdv.visit(exp_node))
+        except Exception as ve:
+            err(str(ve))
+        out("Actual tree:", fg="red")
+        try:
+            exp_node = black.lib2to3_parse(actual)
+            bdv = DebugVisitor()
+            list(bdv.visit(exp_node))
+        except Exception as ve:
+            err(str(ve))
+
+    if actual != expected:
+        out(diff(expected, actual, "expected", "actual"))
+
+    assert actual == expected
+
+
+def assert_format(
+    source: str,
+    expected: str,
+    mode: black.Mode = DEFAULT_MODE,
+    *,
+    fast: bool = False,
+    minimum_version: Optional[Tuple[int, int]] = None,
+) -> None:
+    """Convenience function to check that Black formats as expected.
+
+    You can pass @minimum_version if you're passing code with newer syntax to guard
+    safety guards so they don't just crash with a SyntaxError. Please note this is
+    separate from TargetVerson Mode configuration.
+    """
+    actual = black.format_str(source, mode=mode)
+    _assert_format_equal(expected, actual)
+    # It's not useful to run safety checks if we're expecting no changes anyway. The
+    # assertion right above will raise if reality does actually make changes. This just
+    # avoids wasted CPU cycles.
+    if not fast and source != expected:
+        # Unfortunately the AST equivalence check relies on the built-in ast module
+        # being able to parse the code being formatted. This doesn't always work out
+        # when checking modern code on older versions.
+        if minimum_version is None or sys.version_info >= minimum_version:
+            black.assert_equivalent(source, actual)
+        black.assert_stable(source, actual, mode=mode)
+
+
 def dump_to_stderr(*output: str) -> str:
     return "\n" + "\n".join(output) + "\n"
 
 
 class BlackBaseTestCase(unittest.TestCase):
-    maxDiff = None
-    _diffThreshold = 2 ** 20
-
     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.assertMultiLineEqual(expected, actual)
-
-
-@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
+        _assert_format_equal(expected, actual)
 
 
 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"
-    base_dir = THIS_DIR / "data" if data else PROJECT_ROOT
+    base_dir = DATA_DIR if data else PROJECT_ROOT
     return read_data_from_file(base_dir / name)
 
 
@@ -81,3 +115,14 @@ def read_data_from_file(file_name: Path) -> Tuple[str, str]:
         # 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"
+
+
+@contextmanager
+def change_directory(path: Path) -> Iterator[None]:
+    """Context manager to temporarily chdir to a different directory."""
+    previous_dir = os.getcwd()
+    try:
+        os.chdir(path)
+        yield
+    finally:
+        os.chdir(previous_dir)