Allow setting custom cache directory on all platforms (#2739)

[etc/vim.git] / src / black / __init__.py

diff --git a/src/black/__init__.py b/src/black/__init__.py
index 29fb244f8b751651238fd99fefb055a9ada26eb1..eaf72f9c2b3f4d12ae275d01472112931af331e9 100644 (file)
--- a/src/black/__init__.py
+++ b/src/black/__init__.py
@@ -9,7 +9,8 @@ import io
 from multiprocessing import Manager, freeze_support
 import os
 from pathlib import Path
 from multiprocessing import Manager, freeze_support
 import os
 from pathlib import Path

-import regex as re
+from pathspec.patterns.gitwildmatch import GitWildMatchPatternError
+import re

 import signal
 import sys
 import tokenize
 import signal
 import sys
 import tokenize


@@ -23,22 +24,26 @@ from typing import (
     MutableMapping,
     Optional,
     Pattern,
     MutableMapping,
     Optional,
     Pattern,

+    Sequence,

     Set,
     Sized,
     Tuple,
     Union,
 )
 
     Set,
     Sized,
     Tuple,
     Union,
 )
 

-from dataclasses import replace

 import click
 import click

+from click.core import ParameterSource
+from dataclasses import replace
+from mypy_extensions import mypyc_attr

 
 from black.const import DEFAULT_LINE_LENGTH, DEFAULT_INCLUDES, DEFAULT_EXCLUDES
 from black.const import STDIN_PLACEHOLDER
 from black.nodes import STARS, syms, is_simple_decorator_expression
 
 from black.const import DEFAULT_LINE_LENGTH, DEFAULT_INCLUDES, DEFAULT_EXCLUDES
 from black.const import STDIN_PLACEHOLDER
 from black.nodes import STARS, syms, is_simple_decorator_expression

+from black.nodes import is_string_token

 from black.lines import Line, EmptyLineTracker
 from black.linegen import transform_line, LineGenerator, LN
 from black.comments import normalize_fmt_off
 from black.lines import Line, EmptyLineTracker
 from black.linegen import transform_line, LineGenerator, LN
 from black.comments import normalize_fmt_off

-from black.mode import Mode, TargetVersion
+from black.mode import FUTURE_FLAG_TO_FEATURE, Mode, TargetVersion

 from black.mode import Feature, supports_feature, VERSION_TO_FEATURES
 from black.cache import read_cache, write_cache, get_cache_info, filter_cached, Cache
 from black.concurrency import cancel, shutdown, maybe_install_uvloop
 from black.mode import Feature, supports_feature, VERSION_TO_FEATURES
 from black.cache import read_cache, write_cache, get_cache_info, filter_cached, Cache
 from black.concurrency import cancel, shutdown, maybe_install_uvloop


@@ -55,6 +60,7 @@ from black.handle_ipynb_magics import (
     remove_trailing_semicolon,
     put_trailing_semicolon_back,
     TRANSFORMED_MAGICS,
     remove_trailing_semicolon,
     put_trailing_semicolon_back,
     TRANSFORMED_MAGICS,

+    PYTHON_CELL_MAGICS,

     jupyter_dependencies_are_installed,
 )
 
     jupyter_dependencies_are_installed,
 )
 


@@ -65,6 +71,8 @@ from blib2to3.pgen2 import token
 
 from _black_version import version as __version__
 
 
 from _black_version import version as __version__
 

+COMPILED = Path(__file__).suffix in (".pyd", ".so")
+

 # types
 FileContent = str
 Encoding = str
 # types
 FileContent = str
 Encoding = str


@@ -94,6 +102,8 @@ class WriteBack(Enum):
 # Legacy name, left for integrations.
 FileMode = Mode
 
 # Legacy name, left for integrations.
 FileMode = Mode
 

+DEFAULT_WORKERS = os.cpu_count()
+

 
 def read_pyproject_toml(
     ctx: click.Context, param: click.Parameter, value: Optional[str]
 
 def read_pyproject_toml(
     ctx: click.Context, param: click.Parameter, value: Optional[str]


@@ -113,7 +123,7 @@ def read_pyproject_toml(
     except (OSError, ValueError) as e:
         raise click.FileError(
             filename=value, hint=f"Error reading configuration file: {e}"
     except (OSError, ValueError) as e:
         raise click.FileError(
             filename=value, hint=f"Error reading configuration file: {e}"

-        )
+        ) from None

 
     if not config:
         return None
 
     if not config:
         return None


@@ -167,14 +177,19 @@ def validate_regex(
     ctx: click.Context,
     param: click.Parameter,
     value: Optional[str],
     ctx: click.Context,
     param: click.Parameter,
     value: Optional[str],

-) -> Optional[Pattern]:
+) -> Optional[Pattern[str]]:

     try:
         return re_compile_maybe_verbose(value) if value is not None else None
     try:
         return re_compile_maybe_verbose(value) if value is not None else None

-    except re.error:
-        raise click.BadParameter("Not a valid regular expression")
+    except re.error as e:
+        raise click.BadParameter(f"Not a valid regular expression: {e}") from None

 
 
 
 

-@click.command(context_settings=dict(help_option_names=["-h", "--help"]))
+@click.command(
+    context_settings={"help_option_names": ["-h", "--help"]},
+    # While Click does set this field automatically using the docstring, mypyc
+    # (annoyingly) strips 'em so we need to set it here too.
+    help="The uncompromising code formatter.",
+)

 @click.option("-c", "--code", type=str, help="Format the code passed in as a string.")
 @click.option(
     "-l",
 @click.option("-c", "--code", type=str, help="Format the code passed in as a string.")
 @click.option(
     "-l",


@@ -211,6 +226,16 @@ def validate_regex(
         "(useful when piping source on standard input)."
     ),
 )
         "(useful when piping source on standard input)."
     ),
 )

+@click.option(
+    "--python-cell-magics",
+    multiple=True,
+    help=(
+        "When processing Jupyter Notebooks, add the given magic to the list"
+        f" of known python-magics ({', '.join(PYTHON_CELL_MAGICS)})."
+        " Useful for formatting cells with custom python magics."
+    ),
+    default=[],
+)

 @click.option(
     "-S",
     "--skip-string-normalization",
 @click.option(
     "-S",
     "--skip-string-normalization",


@@ -227,9 +252,14 @@ def validate_regex(
     "--experimental-string-processing",
     is_flag=True,
     hidden=True,
     "--experimental-string-processing",
     is_flag=True,
     hidden=True,

+    help="(DEPRECATED and now included in --preview) Normalize string literals.",
+)
+@click.option(
+    "--preview",
+    is_flag=True,

     help=(
     help=(

-        "Experimental option that performs more normalization on string literals."
-        " Currently disabled because it leads to some crashes."
+        "Enable potentially disruptive style changes that will be added to Black's main"
+        " functionality in the next major release."

     ),
 )
 @click.option(
     ),
 )
 @click.option(


@@ -317,6 +347,14 @@ def validate_regex(
         "editors that rely on using stdin."
     ),
 )
         "editors that rely on using stdin."
     ),
 )

+@click.option(
+    "-W",
+    "--workers",
+    type=click.IntRange(min=1),
+    default=DEFAULT_WORKERS,
+    show_default=True,
+    help="Number of parallel workers",
+)

 @click.option(
     "-q",
     "--quiet",
 @click.option(
     "-q",
     "--quiet",


@@ -335,7 +373,10 @@ def validate_regex(
         " due to exclusion patterns."
     ),
 )
         " due to exclusion patterns."
     ),
 )

-@click.version_option(version=__version__)
+@click.version_option(
+    version=__version__,
+    message=f"%(prog)s, %(version)s (compiled: {'yes' if COMPILED else 'no'})",
+)

 @click.argument(
     "src",
     nargs=-1,
 @click.argument(
     "src",
     nargs=-1,


@@ -371,23 +412,55 @@ def main(
     fast: bool,
     pyi: bool,
     ipynb: bool,
     fast: bool,
     pyi: bool,
     ipynb: bool,

+    python_cell_magics: Sequence[str],

     skip_string_normalization: bool,
     skip_magic_trailing_comma: bool,
     experimental_string_processing: bool,
     skip_string_normalization: bool,
     skip_magic_trailing_comma: bool,
     experimental_string_processing: bool,

+    preview: bool,

     quiet: bool,
     verbose: bool,
     quiet: bool,
     verbose: bool,

-    required_version: str,
-    include: Pattern,
-    exclude: Optional[Pattern],
-    extend_exclude: Optional[Pattern],
-    force_exclude: Optional[Pattern],
+    required_version: Optional[str],
+    include: Pattern[str],
+    exclude: Optional[Pattern[str]],
+    extend_exclude: Optional[Pattern[str]],
+    force_exclude: Optional[Pattern[str]],

     stdin_filename: Optional[str],
     stdin_filename: Optional[str],

+    workers: int,

     src: Tuple[str, ...],
     config: Optional[str],
 ) -> None:
     """The uncompromising code formatter."""
     src: Tuple[str, ...],
     config: Optional[str],
 ) -> None:
     """The uncompromising code formatter."""

-    if config and verbose:
-        out(f"Using configuration from {config}.", bold=False, fg="blue")
+    ctx.ensure_object(dict)
+    root, method = find_project_root(src) if code is None else (None, None)
+    ctx.obj["root"] = root
+
+    if verbose:
+        if root:
+            out(
+                f"Identified `{root}` as project root containing a {method}.",
+                fg="blue",
+            )
+
+            normalized = [
+                (normalize_path_maybe_ignore(Path(source), root), source)
+                for source in src
+            ]
+            srcs_string = ", ".join(
+                [
+                    f'"{_norm}"'
+                    if _norm
+                    else f'\033[31m"{source} (skipping - invalid)"\033[34m'
+                    for _norm, source in normalized
+                ]
+            )
+            out(f"Sources to be formatted: {srcs_string}", fg="blue")
+
+        if config:
+            config_source = ctx.get_parameter_source("config")
+            if config_source in (ParameterSource.DEFAULT, ParameterSource.DEFAULT_MAP):
+                out("Using configuration from project root.", fg="blue")
+            else:
+                out(f"Using configuration in '{config}'.", fg="blue")

 
     error_msg = "Oh no! 💥 💔 💥"
     if required_version and required_version != __version__:
 
     error_msg = "Oh no! 💥 💔 💥"
     if required_version and required_version != __version__:


@@ -414,6 +487,8 @@ def main(
         string_normalization=not skip_string_normalization,
         magic_trailing_comma=not skip_magic_trailing_comma,
         experimental_string_processing=experimental_string_processing,
         string_normalization=not skip_string_normalization,
         magic_trailing_comma=not skip_magic_trailing_comma,
         experimental_string_processing=experimental_string_processing,

+        preview=preview,
+        python_cell_magics=set(python_cell_magics),

     )
 
     if code is not None:
     )
 
     if code is not None:


@@ -428,18 +503,21 @@ def main(
             content=code, fast=fast, write_back=write_back, mode=mode, report=report
         )
     else:
             content=code, fast=fast, write_back=write_back, mode=mode, report=report
         )
     else:

-        sources = get_sources(
-            ctx=ctx,
-            src=src,
-            quiet=quiet,
-            verbose=verbose,
-            include=include,
-            exclude=exclude,
-            extend_exclude=extend_exclude,
-            force_exclude=force_exclude,
-            report=report,
-            stdin_filename=stdin_filename,
-        )
+        try:
+            sources = get_sources(
+                ctx=ctx,
+                src=src,
+                quiet=quiet,
+                verbose=verbose,
+                include=include,
+                exclude=exclude,
+                extend_exclude=extend_exclude,
+                force_exclude=force_exclude,
+                report=report,
+                stdin_filename=stdin_filename,
+            )
+        except GitWildMatchPatternError:
+            ctx.exit(1)

 
         path_empty(
             sources,
 
         path_empty(
             sources,


@@ -464,9 +542,12 @@ def main(
                 write_back=write_back,
                 mode=mode,
                 report=report,
                 write_back=write_back,
                 mode=mode,
                 report=report,

+                workers=workers,

             )
 
     if verbose or not quiet:
             )
 
     if verbose or not quiet:

+        if code is None and (verbose or report.change_count or report.failure_count):
+            out()

         out(error_msg if report.return_code else "All done! ✨ 🍰 ✨")
         if code is None:
             click.echo(str(report), err=True)
         out(error_msg if report.return_code else "All done! ✨ 🍰 ✨")
         if code is None:
             click.echo(str(report), err=True)


@@ -487,14 +568,12 @@ def get_sources(
     stdin_filename: Optional[str],
 ) -> Set[Path]:
     """Compute the set of files to be formatted."""
     stdin_filename: Optional[str],
 ) -> Set[Path]:
     """Compute the set of files to be formatted."""

-
-    root = find_project_root(src)

     sources: Set[Path] = set()
     path_empty(src, "No Path provided. Nothing to do 😴", quiet, verbose, ctx)
 
     if exclude is None:
         exclude = re_compile_maybe_verbose(DEFAULT_EXCLUDES)
     sources: Set[Path] = set()
     path_empty(src, "No Path provided. Nothing to do 😴", quiet, verbose, ctx)
 
     if exclude is None:
         exclude = re_compile_maybe_verbose(DEFAULT_EXCLUDES)

-        gitignore = get_gitignore(root)
+        gitignore = get_gitignore(ctx.obj["root"])

     else:
         gitignore = None
 
     else:
         gitignore = None
 


@@ -507,7 +586,7 @@ def get_sources(
             is_stdin = False
 
         if is_stdin or p.is_file():
             is_stdin = False
 
         if is_stdin or p.is_file():

-            normalized_path = normalize_path_maybe_ignore(p, root, report)
+            normalized_path = normalize_path_maybe_ignore(p, ctx.obj["root"], report)

             if normalized_path is None:
                 continue
 
             if normalized_path is None:
                 continue
 


@@ -534,7 +613,7 @@ def get_sources(
             sources.update(
                 gen_python_files(
                     p.iterdir(),
             sources.update(
                 gen_python_files(
                     p.iterdir(),

-                    root,
+                    ctx.obj["root"],

                     include,
                     exclude,
                     extend_exclude,
                     include,
                     exclude,
                     extend_exclude,


@@ -639,19 +718,28 @@ def reformat_one(
         report.failed(src, str(exc))
 
 
         report.failed(src, str(exc))
 
 

+# diff-shades depends on being to monkeypatch this function to operate. I know it's
+# not ideal, but this shouldn't cause any issues ... hopefully. ~ichard26
+@mypyc_attr(patchable=True)

 def reformat_many(
 def reformat_many(

-    sources: Set[Path], fast: bool, write_back: WriteBack, mode: Mode, report: "Report"
+    sources: Set[Path],
+    fast: bool,
+    write_back: WriteBack,
+    mode: Mode,
+    report: "Report",
+    workers: Optional[int],

 ) -> None:
     """Reformat multiple files using a ProcessPoolExecutor."""
     executor: Executor
     loop = asyncio.get_event_loop()
 ) -> None:
     """Reformat multiple files using a ProcessPoolExecutor."""
     executor: Executor
     loop = asyncio.get_event_loop()

-    worker_count = os.cpu_count()
+    worker_count = workers if workers is not None else DEFAULT_WORKERS

     if sys.platform == "win32":
         # Work around https://bugs.python.org/issue26903
     if sys.platform == "win32":
         # Work around https://bugs.python.org/issue26903

+        assert worker_count is not None

         worker_count = min(worker_count, 60)
     try:
         executor = ProcessPoolExecutor(max_workers=worker_count)
         worker_count = min(worker_count, 60)
     try:
         executor = ProcessPoolExecutor(max_workers=worker_count)

-    except (ImportError, OSError):
+    except (ImportError, NotImplementedError, OSError):

         # we arrive here if the underlying system does not support multi-processing
         # like in AWS Lambda or Termux, in which case we gracefully fallback to
         # a ThreadPoolExecutor with just a single worker (more workers would not do us
         # we arrive here if the underlying system does not support multi-processing
         # like in AWS Lambda or Termux, in which case we gracefully fallback to
         # a ThreadPoolExecutor with just a single worker (more workers would not do us


@@ -742,7 +830,10 @@ async def schedule_formatting(
                     sources_to_cache.append(src)
                 report.done(src, changed)
     if cancelled:
                     sources_to_cache.append(src)
                 report.done(src, changed)
     if cancelled:

-        await asyncio.gather(*cancelled, loop=loop, return_exceptions=True)
+        if sys.version_info >= (3, 7):
+            await asyncio.gather(*cancelled, return_exceptions=True)
+        else:
+            await asyncio.gather(*cancelled, loop=loop, return_exceptions=True)

     if sources_to_cache:
         write_cache(cache, sources_to_cache, mode)
 
     if sources_to_cache:
         write_cache(cache, sources_to_cache, mode)
 


@@ -773,7 +864,9 @@ def format_file_in_place(
     except NothingChanged:
         return False
     except JSONDecodeError:
     except NothingChanged:
         return False
     except JSONDecodeError:

-        raise ValueError(f"File '{src}' cannot be parsed as valid Jupyter notebook.")
+        raise ValueError(
+            f"File '{src}' cannot be parsed as valid Jupyter notebook."
+        ) from None

 
     if write_back == WriteBack.YES:
         with open(src, "w", encoding=encoding, newline=newline) as f:
 
     if write_back == WriteBack.YES:
         with open(src, "w", encoding=encoding, newline=newline) as f:


@@ -901,8 +994,10 @@ def format_file_contents(src_contents: str, *, fast: bool, mode: Mode) -> FileCo
     return dst_contents
 
 
     return dst_contents
 
 

-def validate_cell(src: str) -> None:
-    """Check that cell does not already contain TransformerManager transformations.
+def validate_cell(src: str, mode: Mode) -> None:
+    """Check that cell does not already contain TransformerManager transformations,
+    or non-Python cell magics, which might cause tokenizer_rt to break because of
+    indentations.

 
     If a cell contains ``!ls``, then it'll be transformed to
     ``get_ipython().system('ls')``. However, if the cell originally contained
 
     If a cell contains ``!ls``, then it'll be transformed to
     ``get_ipython().system('ls')``. However, if the cell originally contained


@@ -918,6 +1013,11 @@ def validate_cell(src: str) -> None:
     """
     if any(transformed_magic in src for transformed_magic in TRANSFORMED_MAGICS):
         raise NothingChanged
     """
     if any(transformed_magic in src for transformed_magic in TRANSFORMED_MAGICS):
         raise NothingChanged

+    if (
+        src[:2] == "%%"
+        and src.split()[0][2:] not in PYTHON_CELL_MAGICS | mode.python_cell_magics
+    ):
+        raise NothingChanged

 
 
 def format_cell(src: str, *, fast: bool, mode: Mode) -> str:
 
 
 def format_cell(src: str, *, fast: bool, mode: Mode) -> str:


@@ -936,14 +1036,14 @@ def format_cell(src: str, *, fast: bool, mode: Mode) -> str:
     could potentially be automagics or multi-line magics, which
     are currently not supported.
     """
     could potentially be automagics or multi-line magics, which
     are currently not supported.
     """

-    validate_cell(src)
+    validate_cell(src, mode)

     src_without_trailing_semicolon, has_trailing_semicolon = remove_trailing_semicolon(
         src
     )
     try:
         masked_src, replacements = mask_cell(src_without_trailing_semicolon)
     except SyntaxError:
     src_without_trailing_semicolon, has_trailing_semicolon = remove_trailing_semicolon(
         src
     )
     try:
         masked_src, replacements = mask_cell(src_without_trailing_semicolon)
     except SyntaxError:

-        raise NothingChanged
+        raise NothingChanged from None

     masked_dst = format_str(masked_src, mode=mode)
     if not fast:
         check_stability_and_equivalence(masked_src, masked_dst, mode=mode)
     masked_dst = format_str(masked_src, mode=mode)
     if not fast:
         check_stability_and_equivalence(masked_src, masked_dst, mode=mode)


@@ -953,7 +1053,7 @@ def format_cell(src: str, *, fast: bool, mode: Mode) -> str:
     )
     dst = dst.rstrip("\n")
     if dst == src:
     )
     dst = dst.rstrip("\n")
     if dst == src:

-        raise NothingChanged
+        raise NothingChanged from None

     return dst
 
 
     return dst
 
 


@@ -966,14 +1066,14 @@ def validate_metadata(nb: MutableMapping[str, Any]) -> None:
     """
     language = nb.get("metadata", {}).get("language_info", {}).get("name", None)
     if language is not None and language != "python":
     """
     language = nb.get("metadata", {}).get("language_info", {}).get("name", None)
     if language is not None and language != "python":

-        raise NothingChanged
+        raise NothingChanged from None

 
 
 def format_ipynb_string(src_contents: str, *, fast: bool, mode: Mode) -> FileContent:
     """Format Jupyter notebook.
 
     Operate cell-by-cell, only on code cells, only for Python notebooks.
 
 
 def format_ipynb_string(src_contents: str, *, fast: bool, mode: Mode) -> FileContent:
     """Format Jupyter notebook.
 
     Operate cell-by-cell, only on code cells, only for Python notebooks.

-    If the ``.ipynb`` originally had a trailing newline, it'll be preseved.
+    If the ``.ipynb`` originally had a trailing newline, it'll be preserved.

     """
     trailing_newline = src_contents[-1] == "\n"
     modified = False
     """
     trailing_newline = src_contents[-1] == "\n"
     modified = False


@@ -1034,13 +1134,10 @@ def format_str(src_contents: str, *, mode: Mode) -> FileContent:
     if mode.target_versions:
         versions = mode.target_versions
     else:
     if mode.target_versions:
         versions = mode.target_versions
     else:

-        versions = detect_target_versions(src_node)
+        versions = detect_target_versions(src_node, future_imports=future_imports)
+

     normalize_fmt_off(src_node)
     normalize_fmt_off(src_node)

-    lines = LineGenerator(
-        mode=mode,
-        remove_u_prefix="unicode_literals" in future_imports
-        or supports_feature(versions, Feature.UNICODE_LITERALS),
-    )
+    lines = LineGenerator(mode=mode)

     elt = EmptyLineTracker(is_pyi=mode.is_pyi)
     empty_line = Line(mode=mode)
     after = 0
     elt = EmptyLineTracker(is_pyi=mode.is_pyi)
     empty_line = Line(mode=mode)
     after = 0


@@ -1077,7 +1174,9 @@ def decode_bytes(src: bytes) -> Tuple[FileContent, Encoding, NewLine]:
         return tiow.read(), encoding, newline
 
 
         return tiow.read(), encoding, newline
 
 

-def get_features_used(node: Node) -> Set[Feature]:
+def get_features_used(  # noqa: C901
+    node: Node, *, future_imports: Optional[Set[str]] = None
+) -> Set[Feature]:

     """Return a set of (relatively) new Python features used in this file.
 
     Currently looking for:
     """Return a set of (relatively) new Python features used in this file.
 
     Currently looking for:


@@ -1087,20 +1186,34 @@ def get_features_used(node: Node) -> Set[Feature]:
     - positional only arguments in function signatures and lambdas;
     - assignment expression;
     - relaxed decorator syntax;
     - positional only arguments in function signatures and lambdas;
     - assignment expression;
     - relaxed decorator syntax;

+    - usage of __future__ flags (annotations);
+    - print / exec statements;

     """
     features: Set[Feature] = set()
     """
     features: Set[Feature] = set()

+    if future_imports:
+        features |= {
+            FUTURE_FLAG_TO_FEATURE[future_import]
+            for future_import in future_imports
+            if future_import in FUTURE_FLAG_TO_FEATURE
+        }
+

     for n in node.pre_order():
     for n in node.pre_order():

-        if n.type == token.STRING:
-            value_head = n.value[:2]  # type: ignore
+        if is_string_token(n):
+            value_head = n.value[:2]

             if value_head in {'f"', 'F"', "f'", "F'", "rf", "fr", "RF", "FR"}:
                 features.add(Feature.F_STRINGS)
 
         elif n.type == token.NUMBER:
             if value_head in {'f"', 'F"', "f'", "F'", "rf", "fr", "RF", "FR"}:
                 features.add(Feature.F_STRINGS)
 
         elif n.type == token.NUMBER:

-            if "_" in n.value:  # type: ignore
+            assert isinstance(n, Leaf)
+            if "_" in n.value:

                 features.add(Feature.NUMERIC_UNDERSCORES)
 
         elif n.type == token.SLASH:
                 features.add(Feature.NUMERIC_UNDERSCORES)
 
         elif n.type == token.SLASH:

-            if n.parent and n.parent.type in {syms.typedargslist, syms.arglist}:
+            if n.parent and n.parent.type in {
+                syms.typedargslist,
+                syms.arglist,
+                syms.varargslist,
+            }:

                 features.add(Feature.POS_ONLY_ARGUMENTS)
 
         elif n.type == token.COLONEQUAL:
                 features.add(Feature.POS_ONLY_ARGUMENTS)
 
         elif n.type == token.COLONEQUAL:


@@ -1131,12 +1244,29 @@ def get_features_used(node: Node) -> Set[Feature]:
                         if argch.type in STARS:
                             features.add(feature)
 
                         if argch.type in STARS:
                             features.add(feature)
 

+        elif (
+            n.type in {syms.return_stmt, syms.yield_expr}
+            and len(n.children) >= 2
+            and n.children[1].type == syms.testlist_star_expr
+            and any(child.type == syms.star_expr for child in n.children[1].children)
+        ):
+            features.add(Feature.UNPACKING_ON_FLOW)
+
+        elif (
+            n.type == syms.annassign
+            and len(n.children) >= 4
+            and n.children[3].type == syms.testlist_star_expr
+        ):
+            features.add(Feature.ANN_ASSIGN_EXTENDED_RHS)
+

     return features
 
 
     return features
 
 

-def detect_target_versions(node: Node) -> Set[TargetVersion]:
+def detect_target_versions(
+    node: Node, *, future_imports: Optional[Set[str]] = None
+) -> Set[TargetVersion]:

     """Detect the version to target based on the nodes used."""
     """Detect the version to target based on the nodes used."""

-    features = get_features_used(node)
+    features = get_features_used(node, future_imports=future_imports)

     return {
         version for version in TargetVersion if features <= VERSION_TO_FEATURES[version]
     }
     return {
         version for version in TargetVersion if features <= VERSION_TO_FEATURES[version]
     }


@@ -1198,9 +1328,11 @@ def assert_equivalent(src: str, dst: str, *, pass_num: int = 1) -> None:
         src_ast = parse_ast(src)
     except Exception as exc:
         raise AssertionError(
         src_ast = parse_ast(src)
     except Exception as exc:
         raise AssertionError(

-            "cannot use --safe with this file; failed to parse source file.  AST"
-            f" error message: {exc}"
-        )
+            f"cannot use --safe with this file; failed to parse source file AST: "
+            f"{exc}\n"
+            f"This could be caused by running Black with an older Python version "
+            f"that does not support new syntax used in your source file."
+        ) from exc

 
     try:
         dst_ast = parse_ast(dst)
 
     try:
         dst_ast = parse_ast(dst)


@@ -1261,7 +1393,7 @@ def patch_click() -> None:
     """
     try:
         from click import core
     """
     try:
         from click import core

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

     except ModuleNotFoundError:
         return
 
     except ModuleNotFoundError:
         return