Address feedback & cleanup comments

- I don't actually have to go on a rant about tomli and bare CR it
  turns out.
- Subclassing KeyError isn't actually *that* important for one
  custom exception.

mypy.ini

@@ -41,18 +41,3 @@ follow_imports=skip
 # The following is because of `patch_click()`. Remove when
 # we drop Python 3.6 support.
 warn_unused_ignores=False
-
-[mypy-black.files]
-# Unfortunately tomli has deprecated strings and changed the API type
-# annotations to bytes all while strings still work. We still use strings
-# since it's unclear whether this will last (depends on how much the
-# TOML people like bare CR as a newline sequence I suppose). Anyway,
-# some versions of tomli still specify str as the type so mypy complains
-# that the type: ignore is unnecessary. Gosh I wish I wasn't telling
-# this story.
-#
-# See also: https://github.com/psf/black/pull/2408
-#           https://github.com/pypa/pip/pull/10238 (because black is
-#             following whatever they do)
-#           https://github.com/toml-lang/toml/issues/837
-warn_unused_ignores=False

src/black/__init__.py

@@ -179,6 +179,8 @@ def validate_regex(
 
 @click.command(
     context_settings=dict(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.")

src/black/brackets.py

@@ -49,8 +49,6 @@
 DOT_PRIORITY: Final = 1
 
 
-# Ideally this would be a subclass of KeyError, but mypyc doesn't like that.
-# See also: https://mypyc.readthedocs.io/en/latest/native_classes.html#inheritance.
 class BracketMatchError(Exception):
     """Raised when an opening bracket is unable to be matched to a closing bracket."""
 

src/black/files.py

@@ -95,7 +95,7 @@ def parse_pyproject_toml(path_config: str) -> Dict[str, Any]:
     If parsing fails, will raise a tomli.TOMLDecodeError
     """
     with open(path_config, encoding="utf8") as f:
-        pyproject_toml = tomli.load(f)  # type: ignore  # due to deprecated API usage
+        pyproject_toml = tomli.loads(f.read())
     config = pyproject_toml.get("tool", {}).get("black", {})
     return {k.replace("--", "").replace("-", "_"): v for k, v in config.items()}
 

src/black/handle_ipynb_magics.py

@@ -358,8 +358,8 @@ class OffsetAndMagic:
     magic: str
 
 
-# Unsurprisingly, dataclasses are Not. An. Option. Here. Due. To. Mypyc. As. Usual.
-# > fyi it's due the ast.NodeVisitor parent type
+# Unsurprisingly, subclassing ast.NodeVisitor means we can't use dataclasses here
+# as mypyc will generate broken code.
 class MagicFinder(ast.NodeVisitor):
     """Visit cell to look for get_ipython calls.
 

src/black/linegen.py

@@ -365,9 +365,10 @@ def _rhs(
                 line, line_length=mode.line_length, features=features
             )
 
-        # HACK: functions (like rhs) compiled by mypyc don't retain their __name__
-        # attribute which is needed in `run_transformer` further down. Unfortunately
-        # a nested class breaks mypyc too. So a class must be created via type ...
+        # HACK: nested functions (like _rhs) compiled by mypyc don't retain their
+        # __name__ attribute which is needed in `run_transformer` further down.
+        # Unfortunately a nested class breaks mypyc too. So a class must be created
+        # via type ... https://github.com/mypyc/mypyc/issues/884
         rhs = type("rhs", (), {"__call__": _rhs})()
 
         if mode.experimental_string_processing:

src/black/strings.py

@@ -152,7 +152,10 @@ def normalize_string_prefix(s: str, remove_u_prefix: bool = False) -> str:
     return f"{new_prefix}{match.group(2)}"
 
 
-@lru_cache(maxsize=256)
+# Re(gex) does actually cache patterns internally but this still improves
+# performance on a long list literal of strings by 5-9% since lru_cache's
+# caching overhead is much lower.
+@lru_cache(maxsize=64)
 def _cached_compile(pattern: str) -> re.Pattern:
     return re.compile(pattern)