add --force-exclude option

black.py

@@ -360,6 +360,14 @@ def target_version_option_callback(
     ),
     show_default=True,
 )
+@click.option(
+    "--force-exclude",
+    type=str,
+    help=(
+        "Like --exclude, but in these case files and directories will be excluded "
+        "even when they are passed explicitly as arguments"
+    ),
+)
 @click.option(
     "-q",
     "--quiet",
@@ -412,6 +420,7 @@ def main(
     verbose: bool,
     include: str,
     exclude: str,
+    force_exclude: Optional[str],
     src: Tuple[str, ...],
     config: Optional[str],
 ) -> None:
@@ -453,6 +462,13 @@ def main(
     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 exclude given: {exclude!r}")
+        ctx.exit(2)
     report = Report(check=check, diff=diff, quiet=quiet, verbose=verbose)
     root = find_project_root(src)
     sources: Set[Path] = set()
@@ -461,15 +477,26 @@ def main(
         p = Path(s)
         if p.is_dir():
             sources.update(
-                gen_python_files_in_dir(
-                    p, root, include_regex, exclude_regex, report, get_gitignore(root)
+                gen_python_files(
+                    p.iterdir(),
+                    root,
+                    include_regex,
+                    exclude_regex,
+                    report,
+                    get_gitignore(root),
                 )
             )
-        elif p.is_file() or s == "-":
-            # if a file was explicitly given, we don't care about its extension
+        elif s == "-":
             sources.add(p)
+        elif p.is_file():
+            sources.update(
+                gen_python_files(
+                    [p], root, None, force_exclude_regex, report, get_gitignore(root)
+                )
+            )
         else:
             err(f"invalid path: {s}")
+
     if len(sources) == 0:
         if verbose or not quiet:
             out("No Python files are present to be formatted. Nothing to do 😴")
@@ -3527,11 +3554,11 @@ def get_gitignore(root: Path) -> PathSpec:
     return PathSpec.from_lines("gitwildmatch", lines)
 
 
-def gen_python_files_in_dir(
-    path: Path,
+def gen_python_files(
+    paths: Iterable[Path],
     root: Path,
-    include: Pattern[str],
-    exclude: Pattern[str],
+    include: Optional[Pattern[str]],
+    exclude: Optional[Pattern[str]],
     report: "Report",
     gitignore: PathSpec,
 ) -> Iterator[Path]:
@@ -3543,7 +3570,7 @@ def gen_python_files_in_dir(
     `report` is where output about exclusions goes.
     """
     assert root.is_absolute(), f"INTERNAL ERROR: `root` must be absolute but is {root}"
-    for child in path.iterdir():
+    for child in paths:
         # First ignore files matching .gitignore
         if gitignore.match_file(child.as_posix()):
             report.path_ignored(child, f"matches the .gitignore file content")
@@ -3568,18 +3595,18 @@ def gen_python_files_in_dir(
         if child.is_dir():
             normalized_path += "/"
 
-        exclude_match = exclude.search(normalized_path)
+        exclude_match = exclude.search(normalized_path) if exclude else None
         if exclude_match and exclude_match.group(0):
             report.path_ignored(child, f"matches the --exclude regular expression")
             continue
 
         if child.is_dir():
-            yield from gen_python_files_in_dir(
-                child, root, include, exclude, report, gitignore
+            yield from gen_python_files(
+                child.iterdir(), root, include, exclude, report, gitignore,
             )
 
         elif child.is_file():
-            include_match = include.search(normalized_path)
+            include_match = include.search(normalized_path) if include else True
             if include_match:
                 yield child
 

docs/reference/reference_functions.rst

@@ -61,7 +61,7 @@ File operations
 
 .. autofunction:: black.find_project_root
 
-.. autofunction:: black.gen_python_files_in_dir
+.. autofunction:: black.gen_python_files
 
 .. autofunction:: black.read_pyproject_toml
 

tests/test_black.py

@@ -1442,8 +1442,8 @@ def test_include_exclude(self) -> None:
         ]
         this_abs = THIS_DIR.resolve()
         sources.extend(
-            black.gen_python_files_in_dir(
-                path, this_abs, include, exclude, report, gitignore
+            black.gen_python_files(
+                path.iterdir(), this_abs, include, exclude, report, gitignore
             )
         )
         self.assertEqual(sorted(expected), sorted(sources))
@@ -1463,8 +1463,8 @@ def test_gitignore_exclude(self) -> None:
         ]
         this_abs = THIS_DIR.resolve()
         sources.extend(
-            black.gen_python_files_in_dir(
-                path, this_abs, include, exclude, report, gitignore
+            black.gen_python_files(
+                path.iterdir(), this_abs, include, exclude, report, gitignore
             )
         )
         self.assertEqual(sorted(expected), sorted(sources))
@@ -1488,8 +1488,8 @@ def test_empty_include(self) -> None:
         ]
         this_abs = THIS_DIR.resolve()
         sources.extend(
-            black.gen_python_files_in_dir(
-                path,
+            black.gen_python_files(
+                path.iterdir(),
                 this_abs,
                 empty,
                 re.compile(black.DEFAULT_EXCLUDES),
@@ -1515,8 +1515,8 @@ def test_empty_exclude(self) -> None:
         ]
         this_abs = THIS_DIR.resolve()
         sources.extend(
-            black.gen_python_files_in_dir(
-                path,
+            black.gen_python_files(
+                path.iterdir(),
                 this_abs,
                 re.compile(black.DEFAULT_INCLUDES),
                 empty,
@@ -1575,8 +1575,8 @@ def test_symlink_out_of_root_directory(self) -> None:
         child.is_symlink.return_value = True
         try:
             list(
-                black.gen_python_files_in_dir(
-                    path, root, include, exclude, report, gitignore
+                black.gen_python_files(
+                    path.iterdir(), root, include, exclude, report, gitignore
                 )
             )
         except ValueError as ve:
@@ -1589,8 +1589,8 @@ def test_symlink_out_of_root_directory(self) -> None:
         child.is_symlink.return_value = False
         with self.assertRaises(ValueError):
             list(
-                black.gen_python_files_in_dir(
-                    path, root, include, exclude, report, gitignore
+                black.gen_python_files(
+                    path.iterdir(), root, include, exclude, report, gitignore
                 )
             )
         path.iterdir.assert_called()