Add a fast path for NameSets without wildcards (#241)

When the set of ignored names doesn't use shell-style wildcards, we can
use the faster `frozenset.__contains__` base implementation rather than
the more expensive iteration-based fnmatch'ing approach. This is true
for the default ignore list, and I expect its the more common case by
far even for those who add their own ignored names.

In a simple local benchmark, this results in a 2x speed improvement for
that common (default) path, which I think justifies the small additional
complexity.

Author: jparise

src/pep8ext_naming.py

@@ -55,10 +55,18 @@ def err(self, node, code: str, **kwargs):
 
 
 class NameSet(frozenset[str]):
-    """A set of names that are matched using fnmatchcase."""
-
-    def __contains__(self, item) -> bool:
-        return any(fnmatchcase(item, name) for name in self)
+    """A set of names that can be matched as Unix shell-style wildcards."""
+    _fnmatch: bool = False
+
+    def __new__(cls, iterable: Iterable[str]):
+        obj = super().__new__(cls, iterable)
+        obj._fnmatch = any("*" in s or "?" in s or "[" in s for s in iterable)
+        return obj
+
+    def __contains__(self, item: object, /) -> bool:
+        if self._fnmatch and isinstance(item, str):
+            return any(fnmatchcase(item, name) for name in self)
+        return super().__contains__(item)
 
 
 class _FunctionType: