Add pruning heuristics to PackageFinder based on exclude (#3846)

changelog.d/3846.misc.rst

@@ -0,0 +1 @@
+Add pruning heuristics to ``PackageFinder`` based on ``exclude``.

setuptools/discovery.py

@@ -44,7 +44,6 @@
 from pathlib import Path
 from typing import (
     TYPE_CHECKING,
-    Callable,
     Dict,
     Iterable,
     Iterator,
@@ -61,7 +60,6 @@
 from distutils.util import convert_path
 
 _Path = Union[str, os.PathLike]
-_Filter = Callable[[str], bool]
 StrIter = Iterator[str]
 
 chain_iter = itertools.chain.from_iterable
@@ -75,6 +73,22 @@ def _valid_name(path: _Path) -> bool:
     return os.path.basename(path).isidentifier()
 
 
+class _Filter:
+    """
+    Given a list of patterns, create a callable that will be true only if
+    the input matches at least one of the patterns.
+    """
+
+    def __init__(self, *patterns: str):
+        self._patterns = dict.fromkeys(patterns)
+
+    def __call__(self, item: str) -> bool:
+        return any(fnmatchcase(item, pat) for pat in self._patterns)
+
+    def __contains__(self, item: str) -> bool:
+        return item in self._patterns
+
+
 class _Finder:
     """Base class that exposes functionality for module/package finders"""
 
@@ -111,23 +125,15 @@ def find(
         return list(
             cls._find_iter(
                 convert_path(str(where)),
-                cls._build_filter(*cls.ALWAYS_EXCLUDE, *exclude),
-                cls._build_filter(*include),
+                _Filter(*cls.ALWAYS_EXCLUDE, *exclude),
+                _Filter(*include),
             )
         )
 
     @classmethod
     def _find_iter(cls, where: _Path, exclude: _Filter, include: _Filter) -> StrIter:
         raise NotImplementedError
 
-    @staticmethod
-    def _build_filter(*patterns: str) -> _Filter:
-        """
-        Given a list of patterns, return a callable that will be true only if
-        the input matches at least one of the patterns.
-        """
-        return lambda name: any(fnmatchcase(name, pat) for pat in patterns)
-
 
 class PackageFinder(_Finder):
     """
@@ -160,6 +166,10 @@ def _find_iter(cls, where: _Path, exclude: _Filter, include: _Filter) -> StrIter
                 if include(package) and not exclude(package):
                     yield package
 
+                # Early pruning if there is nothing else to be scanned
+                if f"{package}*" in exclude or f"{package}.*" in exclude:
+                    continue
+
                 # Keep searching subdirectories, as there may be more packages
                 # down there, even if the parent was excluded.
                 dirs.append(dir)