Symlink docs/change_log.md to CHANGES.md, don't copy (#2146)

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

diff --git a/src/black/__init__.py b/src/black/__init__.py
index c1907d9b1f10dd47a19d30df5686d9885fda4fdb..99afc7d3c507fe06d0f21a1f1f50ea4a4b0577ad 100644 (file)
--- a/src/black/__init__.py
+++ b/src/black/__init__.py
@@ -48,7 +48,20 @@ from appdirs import user_cache_dir
 from dataclasses import dataclass, field, replace
 import click
 import toml
 from dataclasses import dataclass, field, replace
 import click
 import toml

-from typed_ast import ast3, ast27
+
+try:
+    from typed_ast import ast3, ast27
+except ImportError:
+    if sys.version_info < (3, 8):
+        print(
+            "The typed_ast package is not installed.\n"
+            "You can install it with `python3 -m pip install typed-ast`.",
+            file=sys.stderr,
+        )
+        sys.exit(1)
+    else:
+        ast3 = ast27 = ast
+

 from pathspec import PathSpec
 
 # lib2to3 fork
 from pathspec import PathSpec
 
 # lib2to3 fork


@@ -69,7 +82,7 @@ if TYPE_CHECKING:
     import colorama  # noqa: F401
 
 DEFAULT_LINE_LENGTH = 88
     import colorama  # noqa: F401
 
 DEFAULT_LINE_LENGTH = 88

-DEFAULT_EXCLUDES = r"/(\.direnv|\.eggs|\.git|\.hg|\.mypy_cache|\.nox|\.tox|\.venv|\.svn|_build|buck-out|build|dist)/"  # noqa: B950
+DEFAULT_EXCLUDES = r"/(\.direnv|\.eggs|\.git|\.hg|\.mypy_cache|\.nox|\.tox|\.venv|venv|\.svn|_build|buck-out|build|dist)/"  # noqa: B950

 DEFAULT_INCLUDES = r"\.pyi?$"
 CACHE_DIR = Path(user_cache_dir("black", version=__version__))
 STDIN_PLACEHOLDER = "__BLACK_STDIN_FILENAME__"
 DEFAULT_INCLUDES = r"\.pyi?$"
 CACHE_DIR = Path(user_cache_dir("black", version=__version__))
 STDIN_PLACEHOLDER = "__BLACK_STDIN_FILENAME__"


@@ -260,9 +273,9 @@ class Mode:
     target_versions: Set[TargetVersion] = field(default_factory=set)
     line_length: int = DEFAULT_LINE_LENGTH
     string_normalization: bool = True
     target_versions: Set[TargetVersion] = field(default_factory=set)
     line_length: int = DEFAULT_LINE_LENGTH
     string_normalization: bool = True

+    is_pyi: bool = False

     magic_trailing_comma: bool = True
     experimental_string_processing: bool = False
     magic_trailing_comma: bool = True
     experimental_string_processing: bool = False

-    is_pyi: bool = False

 
     def get_cache_key(self) -> str:
         if self.target_versions:
 
     def get_cache_key(self) -> str:
         if self.target_versions:


@@ -277,6 +290,8 @@ class Mode:
             str(self.line_length),
             str(int(self.string_normalization)),
             str(int(self.is_pyi)),
             str(self.line_length),
             str(int(self.string_normalization)),
             str(int(self.is_pyi)),

+            str(int(self.magic_trailing_comma)),
+            str(int(self.experimental_string_processing)),

         ]
         return ".".join(parts)
 
         ]
         return ".".join(parts)
 


@@ -289,11 +304,15 @@ def supports_feature(target_versions: Set[TargetVersion], feature: Feature) -> b
     return all(feature in VERSION_TO_FEATURES[version] for version in target_versions)
 
 
     return all(feature in VERSION_TO_FEATURES[version] for version in target_versions)
 
 

-def find_pyproject_toml(path_search_start: Iterable[str]) -> Optional[str]:
+def find_pyproject_toml(path_search_start: Tuple[str, ...]) -> Optional[str]:

     """Find the absolute filepath to a pyproject.toml if it exists"""
     path_project_root = find_project_root(path_search_start)
     path_pyproject_toml = path_project_root / "pyproject.toml"
     """Find the absolute filepath to a pyproject.toml if it exists"""
     path_project_root = find_project_root(path_search_start)
     path_pyproject_toml = path_project_root / "pyproject.toml"

-    return str(path_pyproject_toml) if path_pyproject_toml.is_file() else None
+    if path_pyproject_toml.is_file():
+        return str(path_pyproject_toml)
+
+    path_user_pyproject_toml = find_user_pyproject_toml()
+    return str(path_user_pyproject_toml) if path_user_pyproject_toml.is_file() else None

 
 
 def parse_pyproject_toml(path_config: str) -> Dict[str, Any]:
 
 
 def parse_pyproject_toml(path_config: str) -> Dict[str, Any]:


@@ -363,6 +382,17 @@ def target_version_option_callback(
     return [TargetVersion[val.upper()] for val in v]
 
 
     return [TargetVersion[val.upper()] for val in v]
 
 

+def validate_regex(
+    ctx: click.Context,
+    param: click.Parameter,
+    value: Optional[str],
+) -> Optional[Pattern]:
+    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")
+
+

 @click.command(context_settings=dict(help_option_names=["-h", "--help"]))
 @click.option("-c", "--code", type=str, help="Format the code passed in as a string.")
 @click.option(
 @click.command(context_settings=dict(help_option_names=["-h", "--help"]))
 @click.option("-c", "--code", type=str, help="Format the code passed in as a string.")
 @click.option(


@@ -417,8 +447,8 @@ def target_version_option_callback(
     "--check",
     is_flag=True,
     help=(
     "--check",
     is_flag=True,
     help=(

-        "Don't write the files back, just return the status.  Return code 0 means"
-        " nothing would change.  Return code 1 means some files would be reformatted."
+        "Don't write the files back, just return the status. Return code 0 means"
+        " nothing would change. Return code 1 means some files would be reformatted."

         " Return code 123 means there was an internal error."
     ),
 )
         " Return code 123 means there was an internal error."
     ),
 )


@@ -441,11 +471,12 @@ def target_version_option_callback(
     "--include",
     type=str,
     default=DEFAULT_INCLUDES,
     "--include",
     type=str,
     default=DEFAULT_INCLUDES,

+    callback=validate_regex,

     help=(
         "A regular expression that matches files and directories that should be"
     help=(
         "A regular expression that matches files and directories that should be"

-        " included on recursive searches.  An empty value means all files are included"
-        " regardless of the name.  Use forward slashes for directories on all platforms"
-        " (Windows, too).  Exclusions are calculated first, inclusions later."
+        " included on recursive searches. An empty value means all files are included"
+        " regardless of the name. Use forward slashes for directories on all platforms"
+        " (Windows, too). Exclusions are calculated first, inclusions later."

     ),
     show_default=True,
 )
     ),
     show_default=True,
 )


@@ -453,17 +484,28 @@ def target_version_option_callback(
     "--exclude",
     type=str,
     default=DEFAULT_EXCLUDES,
     "--exclude",
     type=str,
     default=DEFAULT_EXCLUDES,

+    callback=validate_regex,

     help=(
         "A regular expression that matches files and directories that should be"
     help=(
         "A regular expression that matches files and directories that should be"

-        " excluded on recursive searches.  An empty value means no paths are excluded."
-        " Use forward slashes for directories on all platforms (Windows, too). "
+        " excluded on recursive searches. An empty value means no paths are excluded."
+        " Use forward slashes for directories on all platforms (Windows, too)."

         " Exclusions are calculated first, inclusions later."
     ),
     show_default=True,
 )
         " Exclusions are calculated first, inclusions later."
     ),
     show_default=True,
 )

+@click.option(
+    "--extend-exclude",
+    type=str,
+    callback=validate_regex,
+    help=(
+        "Like --exclude, but adds additional files and directories on top of the"
+        " excluded ones. (Useful if you simply want to add to the default)"
+    ),
+)

 @click.option(
     "--force-exclude",
     type=str,
 @click.option(
     "--force-exclude",
     type=str,

+    callback=validate_regex,

     help=(
         "Like --exclude, but files and directories matching this regex will be "
         "excluded even when they are passed explicitly as arguments."
     help=(
         "Like --exclude, but files and directories matching this regex will be "
         "excluded even when they are passed explicitly as arguments."


@@ -493,7 +535,7 @@ def target_version_option_callback(
     is_flag=True,
     help=(
         "Also emit messages to stderr about files that were not changed or were ignored"
     is_flag=True,
     help=(
         "Also emit messages to stderr about files that were not changed or were ignored"

-        " due to --exclude=."
+        " due to exclusion patterns."

     ),
 )
 @click.version_option(version=__version__)
     ),
 )
 @click.version_option(version=__version__)


@@ -535,9 +577,10 @@ def main(
     experimental_string_processing: bool,
     quiet: bool,
     verbose: bool,
     experimental_string_processing: bool,
     quiet: bool,
     verbose: bool,

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

     stdin_filename: Optional[str],
     src: Tuple[str, ...],
     config: Optional[str],
     stdin_filename: Optional[str],
     src: Tuple[str, ...],
     config: Optional[str],


@@ -570,6 +613,7 @@ def main(
         verbose=verbose,
         include=include,
         exclude=exclude,
         verbose=verbose,
         include=include,
         exclude=exclude,

+        extend_exclude=extend_exclude,

         force_exclude=force_exclude,
         report=report,
         stdin_filename=stdin_filename,
         force_exclude=force_exclude,
         report=report,
         stdin_filename=stdin_filename,


@@ -608,30 +652,14 @@ def get_sources(
     src: Tuple[str, ...],
     quiet: bool,
     verbose: bool,
     src: Tuple[str, ...],
     quiet: bool,
     verbose: bool,

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

     report: "Report",
     stdin_filename: Optional[str],
 ) -> Set[Path]:
     """Compute the set of files to be formatted."""
     report: "Report",
     stdin_filename: Optional[str],
 ) -> Set[Path]:
     """Compute the set of files to be formatted."""

-    try:
-        include_regex = re_compile_maybe_verbose(include)
-    except re.error:
-        err(f"Invalid regular expression for include given: {include!r}")
-        ctx.exit(2)
-    try:
-        exclude_regex = re_compile_maybe_verbose(exclude)
-    except re.error:
-        err(f"Invalid regular expression for exclude given: {exclude!r}")
-        ctx.exit(2)
-    try:
-        force_exclude_regex = (
-            re_compile_maybe_verbose(force_exclude) if force_exclude else None
-        )
-    except re.error:
-        err(f"Invalid regular expression for force_exclude given: {force_exclude!r}")
-        ctx.exit(2)

 
     root = find_project_root(src)
     sources: Set[Path] = set()
 
     root = find_project_root(src)
     sources: Set[Path] = set()


@@ -653,8 +681,8 @@ def get_sources(
 
             normalized_path = "/" + normalized_path
             # Hard-exclude any files that matches the `--force-exclude` regex.
 
             normalized_path = "/" + normalized_path
             # Hard-exclude any files that matches the `--force-exclude` regex.

-            if force_exclude_regex:
-                force_exclude_match = force_exclude_regex.search(normalized_path)
+            if force_exclude:
+                force_exclude_match = force_exclude.search(normalized_path)

             else:
                 force_exclude_match = None
             if force_exclude_match and force_exclude_match.group(0):
             else:
                 force_exclude_match = None
             if force_exclude_match and force_exclude_match.group(0):


@@ -670,9 +698,10 @@ def get_sources(
                 gen_python_files(
                     p.iterdir(),
                     root,
                 gen_python_files(
                     p.iterdir(),
                     root,

-                    include_regex,
-                    exclude_regex,
-                    force_exclude_regex,
+                    include,
+                    exclude,
+                    extend_exclude,
+                    force_exclude,

                     report,
                     gitignore,
                 )
                     report,
                     gitignore,
                 )


@@ -757,7 +786,7 @@ def reformat_many(
     except (ImportError, 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
     except (ImportError, 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 ThreadPollExecutor with just a single worker (more workers would not do us
+        # a ThreadPoolExecutor with just a single worker (more workers would not do us

         # any good due to the Global Interpreter Lock)
         executor = ThreadPoolExecutor(max_workers=1)
 
         # any good due to the Global Interpreter Lock)
         executor = ThreadPoolExecutor(max_workers=1)
 


@@ -820,7 +849,7 @@ async def schedule_formatting(
         ): src
         for src in sorted(sources)
     }
         ): src
         for src in sorted(sources)
     }

-    pending: Iterable["asyncio.Future[bool]"] = tasks.keys()
+    pending = tasks.keys()

     try:
         loop.add_signal_handler(signal.SIGINT, cancel, pending)
         loop.add_signal_handler(signal.SIGTERM, cancel, pending)
     try:
         loop.add_signal_handler(signal.SIGINT, cancel, pending)
         loop.add_signal_handler(signal.SIGTERM, cancel, pending)


@@ -883,7 +912,7 @@ def format_file_in_place(
         dst_name = f"{src}\t{now} +0000"
         diff_contents = diff(src_contents, dst_contents, src_name, dst_name)
 
         dst_name = f"{src}\t{now} +0000"
         diff_contents = diff(src_contents, dst_contents, src_name, dst_name)
 

-        if write_back == write_back.COLOR_DIFF:
+        if write_back == WriteBack.COLOR_DIFF:

             diff_contents = color_diff(diff_contents)
 
         with lock or nullcontext():
             diff_contents = color_diff(diff_contents)
 
         with lock or nullcontext():


@@ -989,7 +1018,17 @@ def format_file_contents(src_contents: str, *, fast: bool, mode: Mode) -> FileCo
 
     if not fast:
         assert_equivalent(src_contents, dst_contents)
 
     if not fast:
         assert_equivalent(src_contents, dst_contents)

-        assert_stable(src_contents, dst_contents, mode=mode)
+
+        # Forced second pass to work around optional trailing commas (becoming
+        # forced trailing commas on pass 2) interacting differently with optional
+        # parentheses.  Admittedly ugly.
+        dst_contents_pass2 = format_str(dst_contents, mode=mode)
+        if dst_contents != dst_contents_pass2:
+            dst_contents = dst_contents_pass2
+            assert_equivalent(src_contents, dst_contents, pass_num=2)
+            assert_stable(src_contents, dst_contents, mode=mode)
+        # Note: no need to explicitly call `assert_stable` if `dst_contents` was
+        # the same as `dst_contents_pass2`.

     return dst_contents
 
 
     return dst_contents
 
 


@@ -1480,7 +1519,7 @@ class Line:
     comments: Dict[LeafID, List[Leaf]] = field(default_factory=dict)
     bracket_tracker: BracketTracker = field(default_factory=BracketTracker)
     inside_brackets: bool = False
     comments: Dict[LeafID, List[Leaf]] = field(default_factory=dict)
     bracket_tracker: BracketTracker = field(default_factory=BracketTracker)
     inside_brackets: bool = False

-    should_split: bool = False
+    should_split_rhs: bool = False

     magic_trailing_comma: Optional[Leaf] = None
 
     def append(self, leaf: Leaf, preformatted: bool = False) -> None:
     magic_trailing_comma: Optional[Leaf] = None
 
     def append(self, leaf: Leaf, preformatted: bool = False) -> None:


@@ -1792,7 +1831,7 @@ class Line:
             mode=self.mode,
             depth=self.depth,
             inside_brackets=self.inside_brackets,
             mode=self.mode,
             depth=self.depth,
             inside_brackets=self.inside_brackets,

-            should_split=self.should_split,
+            should_split_rhs=self.should_split_rhs,

             magic_trailing_comma=self.magic_trailing_comma,
         )
 
             magic_trailing_comma=self.magic_trailing_comma,
         )
 


@@ -2049,6 +2088,8 @@ class LineGenerator(Visitor[Line]):
 
     def visit_simple_stmt(self, node: Node) -> Iterator[Line]:
         """Visit a statement without nested statements."""
 
     def visit_simple_stmt(self, node: Node) -> Iterator[Line]:
         """Visit a statement without nested statements."""

+        if first_child_is_arith(node):
+            wrap_in_parentheses(node, node.children[0], visible=False)

         is_suite_like = node.parent and node.parent.type in STATEMENT
         if is_suite_like:
             if self.mode.is_pyi and is_stub_body(node):
         is_suite_like = node.parent and node.parent.type in STATEMENT
         if is_suite_like:
             if self.mode.is_pyi and is_stub_body(node):


@@ -2124,16 +2165,35 @@ class LineGenerator(Visitor[Line]):
             # We're ignoring docstrings with backslash newline escapes because changing
             # indentation of those changes the AST representation of the code.
             prefix = get_string_prefix(leaf.value)
             # We're ignoring docstrings with backslash newline escapes because changing
             # indentation of those changes the AST representation of the code.
             prefix = get_string_prefix(leaf.value)

-            lead_len = len(prefix) + 3
-            tail_len = -3
-            indent = " " * 4 * self.current_line.depth
-            docstring = fix_docstring(leaf.value[lead_len:tail_len], indent)
+            docstring = leaf.value[len(prefix) :]  # Remove the prefix
+            quote_char = docstring[0]
+            # A natural way to remove the outer quotes is to do:
+            #   docstring = docstring.strip(quote_char)
+            # but that breaks on """""x""" (which is '""x').
+            # So we actually need to remove the first character and the next two
+            # characters but only if they are the same as the first.
+            quote_len = 1 if docstring[1] != quote_char else 3
+            docstring = docstring[quote_len:-quote_len]
+
+            if is_multiline_string(leaf):
+                indent = " " * 4 * self.current_line.depth
+                docstring = fix_docstring(docstring, indent)
+            else:
+                docstring = docstring.strip()
+

             if docstring:
             if docstring:

-                if leaf.value[lead_len - 1] == docstring[0]:
+                # Add some padding if the docstring starts / ends with a quote mark.
+                if docstring[0] == quote_char:

                     docstring = " " + docstring
                     docstring = " " + docstring

-                if leaf.value[tail_len + 1] == docstring[-1]:
+                if docstring[-1] == quote_char:

                     docstring = docstring + " "
                     docstring = docstring + " "

-            leaf.value = leaf.value[0:lead_len] + docstring + leaf.value[tail_len:]
+            else:
+                # Add some padding if the docstring is empty.
+                docstring = " "
+
+            # We could enforce triple quotes at this point.
+            quote = quote_char * quote_len
+            leaf.value = prefix + quote + docstring + quote

 
         yield from self.visit_default(leaf)
 
 
         yield from self.visit_default(leaf)
 


@@ -2680,6 +2740,13 @@ def make_comment(content: str) -> str:
 
     if content[0] == "#":
         content = content[1:]
 
     if content[0] == "#":
         content = content[1:]

+    NON_BREAKING_SPACE = " "
+    if (
+        content
+        and content[0] == NON_BREAKING_SPACE
+        and not content.lstrip().startswith("type:")
+    ):
+        content = " " + content[1:]  # Replace NBSP by a simple space

     if content and content[0] not in " !:#'%":
         content = " " + content
     return "#" + content
     if content and content[0] not in " !:#'%":
         content = " " + content
     return "#" + content


@@ -2712,7 +2779,7 @@ def transform_line(
     transformers: List[Transformer]
     if (
         not line.contains_uncollapsable_type_comments()
     transformers: List[Transformer]
     if (
         not line.contains_uncollapsable_type_comments()

-        and not line.should_split
+        and not line.should_split_rhs

         and not line.magic_trailing_comma
         and (
             is_line_short_enough(line, line_length=mode.line_length, line_str=line_str)
         and not line.magic_trailing_comma
         and (
             is_line_short_enough(line, line_length=mode.line_length, line_str=line_str)


@@ -4387,7 +4454,7 @@ class StringParenWrapper(CustomSplitMapMixin, BaseStringSplitter):
             mode=line.mode,
             depth=line.depth + 1,
             inside_brackets=True,
             mode=line.mode,
             depth=line.depth + 1,
             inside_brackets=True,

-            should_split=line.should_split,
+            should_split_rhs=line.should_split_rhs,

             magic_trailing_comma=line.magic_trailing_comma,
         )
         string_leaf = Leaf(token.STRING, string_value)
             magic_trailing_comma=line.magic_trailing_comma,
         )
         string_leaf = Leaf(token.STRING, string_value)


@@ -5010,7 +5077,7 @@ def bracket_split_build_line(
         for comment_after in original.comments_after(leaf):
             result.append(comment_after, preformatted=True)
     if is_body and should_split_line(result, opening_bracket):
         for comment_after in original.comments_after(leaf):
             result.append(comment_after, preformatted=True)
     if is_body and should_split_line(result, opening_bracket):

-        result.should_split = True
+        result.should_split_rhs = True

     return result
 
 
     return result
 
 


@@ -5296,15 +5363,10 @@ def normalize_numeric_literal(leaf: Leaf) -> None:
 
 def format_hex(text: str) -> str:
     """
 
 def format_hex(text: str) -> str:
     """

-    Formats a hexadecimal string like "0x12b3"
-
-    Uses lowercase because of similarity between "B" and "8", which
-    can cause security issues.
-    see: https://github.com/psf/black/issues/1692
+    Formats a hexadecimal string like "0x12B3"

     """
     """

-

     before, after = text[:2], text[2:]
     before, after = text[:2], text[2:]

-    return f"{before}{after.lower()}"
+    return f"{before}{after.upper()}"

 
 
 def format_scientific_notation(text: str) -> str:
 
 
 def format_scientific_notation(text: str) -> str:


@@ -5368,10 +5430,7 @@ def normalize_invisible_parens(node: Node, parens_after: Set[str]) -> None:
             check_lpar = True
 
         if check_lpar:
             check_lpar = True
 
         if check_lpar:

-            if is_walrus_assignment(child):
-                pass
-
-            elif child.type == syms.atom:
+            if child.type == syms.atom:

                 if maybe_make_parens_invisible_in_atom(child, parent=node):
                     wrap_in_parentheses(node, child, visible=False)
             elif is_one_tuple(child):
                 if maybe_make_parens_invisible_in_atom(child, parent=node):
                     wrap_in_parentheses(node, child, visible=False)
             elif is_one_tuple(child):


@@ -5543,6 +5602,7 @@ def maybe_make_parens_invisible_in_atom(node: LN, parent: LN) -> bool:
     Returns whether the node should itself be wrapped in invisible parentheses.
 
     """
     Returns whether the node should itself be wrapped in invisible parentheses.
 
     """

+

     if (
         node.type != syms.atom
         or is_empty_tuple(node)
     if (
         node.type != syms.atom
         or is_empty_tuple(node)


@@ -5552,6 +5612,15 @@ def maybe_make_parens_invisible_in_atom(node: LN, parent: LN) -> bool:
     ):
         return False
 
     ):
         return False
 

+    if is_walrus_assignment(node):
+        if parent.type in [
+            syms.annassign,
+            syms.expr_stmt,
+            syms.assert_stmt,
+            syms.return_stmt,
+        ]:
+            return False
+

     first = node.children[0]
     last = node.children[-1]
     if first.type == token.LPAR and last.type == token.RPAR:
     first = node.children[0]
     last = node.children[-1]
     if first.type == token.LPAR and last.type == token.RPAR:


@@ -5613,6 +5682,17 @@ def unwrap_singleton_parenthesis(node: LN) -> Optional[LN]:
     return wrapped
 
 
     return wrapped
 
 

+def first_child_is_arith(node: Node) -> bool:
+    """Whether first child is an arithmetic or a binary arithmetic expression"""
+    expr_types = {
+        syms.arith_expr,
+        syms.shift_expr,
+        syms.xor_expr,
+        syms.and_expr,
+    }
+    return bool(node.children and node.children[0].type in expr_types)
+
+

 def wrap_in_parentheses(parent: Node, child: LN, *, visible: bool = True) -> None:
     """Wrap `child` in parentheses.
 
 def wrap_in_parentheses(parent: Node, child: LN, *, visible: bool = True) -> None:
     """Wrap `child` in parentheses.
 


@@ -6064,7 +6144,7 @@ def get_future_imports(node: Node) -> Set[str]:
 
 @lru_cache()
 def get_gitignore(root: Path) -> PathSpec:
 
 @lru_cache()
 def get_gitignore(root: Path) -> PathSpec:

-    """ Return a PathSpec matching gitignore content if present."""
+    """Return a PathSpec matching gitignore content if present."""

     gitignore = root / ".gitignore"
     lines: List[str] = []
     if gitignore.is_file():
     gitignore = root / ".gitignore"
     lines: List[str] = []
     if gitignore.is_file():


@@ -6097,17 +6177,27 @@ def normalize_path_maybe_ignore(
     return normalized_path
 
 
     return normalized_path
 
 

+def path_is_excluded(
+    normalized_path: str,
+    pattern: Optional[Pattern[str]],
+) -> bool:
+    match = pattern.search(normalized_path) if pattern else None
+    return bool(match and match.group(0))
+
+

 def gen_python_files(
     paths: Iterable[Path],
     root: Path,
     include: Optional[Pattern[str]],
     exclude: Pattern[str],
 def gen_python_files(
     paths: Iterable[Path],
     root: Path,
     include: Optional[Pattern[str]],
     exclude: Pattern[str],

+    extend_exclude: Optional[Pattern[str]],

     force_exclude: Optional[Pattern[str]],
     report: "Report",
     gitignore: PathSpec,
 ) -> Iterator[Path]:
     """Generate all files under `path` whose paths are not excluded by the
     force_exclude: Optional[Pattern[str]],
     report: "Report",
     gitignore: PathSpec,
 ) -> Iterator[Path]:
     """Generate all files under `path` whose paths are not excluded by the

-    `exclude_regex` or `force_exclude` regexes, but are included by the `include` regex.
+    `exclude_regex`, `extend_exclude`, or `force_exclude` regexes,
+    but are included by the `include` regex.

 
     Symbolic links pointing outside of the `root` directory are ignored.
 
 
     Symbolic links pointing outside of the `root` directory are ignored.
 


@@ -6124,20 +6214,22 @@ def gen_python_files(
             report.path_ignored(child, "matches the .gitignore file content")
             continue
 
             report.path_ignored(child, "matches the .gitignore file content")
             continue
 

-        # Then ignore with `--exclude` and `--force-exclude` options.
+        # Then ignore with `--exclude` `--extend-exclude` and `--force-exclude` options.

         normalized_path = "/" + normalized_path
         if child.is_dir():
             normalized_path += "/"
 
         normalized_path = "/" + normalized_path
         if child.is_dir():
             normalized_path += "/"
 

-        exclude_match = exclude.search(normalized_path) if exclude else None
-        if exclude_match and exclude_match.group(0):
+        if path_is_excluded(normalized_path, exclude):

             report.path_ignored(child, "matches the --exclude regular expression")
             continue
 
             report.path_ignored(child, "matches the --exclude regular expression")
             continue
 

-        force_exclude_match = (
-            force_exclude.search(normalized_path) if force_exclude else None
-        )
-        if force_exclude_match and force_exclude_match.group(0):
+        if path_is_excluded(normalized_path, extend_exclude):
+            report.path_ignored(
+                child, "matches the --extend-exclude regular expression"
+            )
+            continue
+
+        if path_is_excluded(normalized_path, force_exclude):

             report.path_ignored(child, "matches the --force-exclude regular expression")
             continue
 
             report.path_ignored(child, "matches the --force-exclude regular expression")
             continue
 


@@ -6147,6 +6239,7 @@ def gen_python_files(
                 root,
                 include,
                 exclude,
                 root,
                 include,
                 exclude,

+                extend_exclude,

                 force_exclude,
                 report,
                 gitignore,
                 force_exclude,
                 report,
                 gitignore,


@@ -6159,7 +6252,7 @@ def gen_python_files(
 
 
 @lru_cache()
 
 
 @lru_cache()

-def find_project_root(srcs: Iterable[str]) -> Path:
+def find_project_root(srcs: Tuple[str, ...]) -> Path:

     """Return a directory containing .git, .hg, or pyproject.toml.
 
     That directory will be a common parent of all files and directories
     """Return a directory containing .git, .hg, or pyproject.toml.
 
     That directory will be a common parent of all files and directories


@@ -6197,6 +6290,22 @@ def find_project_root(srcs: Iterable[str]) -> Path:
     return directory
 
 
     return directory
 
 

+@lru_cache()
+def find_user_pyproject_toml() -> Path:
+    r"""Return the path to the top-level user configuration for black.
+
+    This looks for ~\.black on Windows and ~/.config/black on Linux and other
+    Unix systems.
+    """
+    if sys.platform == "win32":
+        # Windows
+        user_config_path = Path.home() / ".black"
+    else:
+        config_root = os.environ.get("XDG_CONFIG_HOME", "~/.config")
+        user_config_path = Path(config_root).expanduser() / "black"
+    return user_config_path.resolve()
+
+

 @dataclass
 class Report:
     """Provides a reformatting counter. Can be rendered with `str(report)`."""
 @dataclass
 class Report:
     """Provides a reformatting counter. Can be rendered with `str(report)`."""


@@ -6298,7 +6407,12 @@ def parse_ast(src: str) -> Union[ast.AST, ast3.AST, ast27.AST]:
                 return ast3.parse(src, filename, feature_version=feature_version)
             except SyntaxError:
                 continue
                 return ast3.parse(src, filename, feature_version=feature_version)
             except SyntaxError:
                 continue

-
+    if ast27.__name__ == "ast":
+        raise SyntaxError(
+            "The requested source code has invalid Python 3 syntax.\n"
+            "If you are trying to format Python 2 files please reinstall Black"
+            " with the 'python2' extra: `python3 -m pip install black[python2]`."
+        )

     return ast27.parse(src)
 
 
     return ast27.parse(src)
 
 


@@ -6364,12 +6478,22 @@ def _stringify_ast(
             # Constant strings may be indented across newlines, if they are
             # docstrings; fold spaces after newlines when comparing. Similarly,
             # trailing and leading space may be removed.
             # Constant strings may be indented across newlines, if they are
             # docstrings; fold spaces after newlines when comparing. Similarly,
             # trailing and leading space may be removed.

+            # Note that when formatting Python 2 code, at least with Windows
+            # line-endings, docstrings can end up here as bytes instead of
+            # str so make sure that we handle both cases.

             if (
                 isinstance(node, ast.Constant)
                 and field == "value"
             if (
                 isinstance(node, ast.Constant)
                 and field == "value"

-                and isinstance(value, str)
+                and isinstance(value, (str, bytes))

             ):
             ):

-                normalized = re.sub(r" *\n[ \t]*", "\n", value).strip()
+                lineend = "\n" if isinstance(value, str) else b"\n"
+                # To normalize, we strip any leading and trailing space from
+                # each line...
+                stripped = [line.strip() for line in value.splitlines()]
+                normalized = lineend.join(stripped)  # type: ignore[attr-defined]
+                # ...and remove any blank lines at the beginning and end of
+                # the whole string
+                normalized = normalized.strip()

             else:
                 normalized = value
             yield f"{'  ' * (depth+2)}{normalized!r},  # {value.__class__.__name__}"
             else:
                 normalized = value
             yield f"{'  ' * (depth+2)}{normalized!r},  # {value.__class__.__name__}"


@@ -6377,7 +6501,7 @@ def _stringify_ast(
     yield f"{'  ' * depth})  # /{node.__class__.__name__}"
 
 
     yield f"{'  ' * depth})  # /{node.__class__.__name__}"
 
 

-def assert_equivalent(src: str, dst: str) -> None:
+def assert_equivalent(src: str, dst: str, *, pass_num: int = 1) -> None:

     """Raise AssertionError if `src` and `dst` aren't equivalent."""
     try:
         src_ast = parse_ast(src)
     """Raise AssertionError if `src` and `dst` aren't equivalent."""
     try:
         src_ast = parse_ast(src)


@@ -6392,9 +6516,9 @@ def assert_equivalent(src: str, dst: str) -> None:
     except Exception as exc:
         log = dump_to_file("".join(traceback.format_tb(exc.__traceback__)), dst)
         raise AssertionError(
     except Exception as exc:
         log = dump_to_file("".join(traceback.format_tb(exc.__traceback__)), dst)
         raise AssertionError(

-            f"INTERNAL ERROR: Black produced invalid code: {exc}. Please report a bug"
-            " on https://github.com/psf/black/issues.  This invalid output might be"
-            f" helpful: {log}"
+            f"INTERNAL ERROR: Black produced invalid code on pass {pass_num}: {exc}. "
+            "Please report a bug on https://github.com/psf/black/issues.  "
+            f"This invalid output might be helpful: {log}"

         ) from None
 
     src_ast_str = "\n".join(_stringify_ast(src_ast))
         ) from None
 
     src_ast_str = "\n".join(_stringify_ast(src_ast))


@@ -6403,8 +6527,8 @@ def assert_equivalent(src: str, dst: str) -> None:
         log = dump_to_file(diff(src_ast_str, dst_ast_str, "src", "dst"))
         raise AssertionError(
             "INTERNAL ERROR: Black produced code that is not equivalent to the"
         log = dump_to_file(diff(src_ast_str, dst_ast_str, "src", "dst"))
         raise AssertionError(
             "INTERNAL ERROR: Black produced code that is not equivalent to the"

-            " source.  Please report a bug on https://github.com/psf/black/issues. "
-            f" This diff might be helpful: {log}"
+            f" source on pass {pass_num}.  Please report a bug on "
+            f"https://github.com/psf/black/issues.  This diff might be helpful: {log}"

         ) from None
 
 
         ) from None
 
 


@@ -6870,11 +6994,6 @@ def patched_main() -> None:
 
 
 def is_docstring(leaf: Leaf) -> bool:
 
 
 def is_docstring(leaf: Leaf) -> bool:

-    if not is_multiline_string(leaf):
-        # For the purposes of docstring re-indentation, we don't need to do anything
-        # with single-line docstrings.
-        return False
-

     if prev_siblings_are(
         leaf.parent, [None, token.NEWLINE, token.INDENT, syms.simple_stmt]
     ):
     if prev_siblings_are(
         leaf.parent, [None, token.NEWLINE, token.INDENT, syms.simple_stmt]
     ):