Move *PackageFinder to the new 'discovery' module

Following up the discussion in pypa#2887 and pypa#2329, it seems that setuptools
is moving towards more automatic discovery features.

PackageFinder and PEP420PackageFinder are fundamental pieces of this
puzzle and grouping together them togheter with the code implementing these
new discovery features make a lot of sense.

setuptools/__init__.py

@@ -1,6 +1,5 @@
 """Extensions to the 'distutils' for large or complex distributions"""
 
-from fnmatch import fnmatchcase
 import functools
 import os
 import re
@@ -9,14 +8,14 @@
 
 import distutils.core
 from distutils.errors import DistutilsOptionError
-from distutils.util import convert_path
 
 from ._deprecation_warning import SetuptoolsDeprecationWarning
 
 import setuptools.version
 from setuptools.extension import Extension
 from setuptools.dist import Distribution
 from setuptools.depends import Require
+from setuptools.discovery import PackageFinder, PEP420PackageFinder
 from . import monkey
 from . import logging
 
@@ -37,85 +36,6 @@
 bootstrap_install_from = None
 
 
-class PackageFinder:
-    """
-    Generate a list of all Python packages found within a directory
-    """
-
-    @classmethod
-    def find(cls, where='.', exclude=(), include=('*',)):
-        """Return a list all Python packages found within directory 'where'
-
-        'where' is the root directory which will be searched for packages.  It
-        should be supplied as a "cross-platform" (i.e. URL-style) path; it will
-        be converted to the appropriate local path syntax.
-
-        'exclude' is a sequence of package names to exclude; '*' can be used
-        as a wildcard in the names, such that 'foo.*' will exclude all
-        subpackages of 'foo' (but not 'foo' itself).
-
-        'include' is a sequence of package names to include.  If it's
-        specified, only the named packages will be included.  If it's not
-        specified, all found packages will be included.  'include' can contain
-        shell style wildcard patterns just like 'exclude'.
-        """
-
-        return list(
-            cls._find_packages_iter(
-                convert_path(where),
-                cls._build_filter('ez_setup', '*__pycache__', *exclude),
-                cls._build_filter(*include),
-            )
-        )
-
-    @classmethod
-    def _find_packages_iter(cls, where, exclude, include):
-        """
-        All the packages found in 'where' that pass the 'include' filter, but
-        not the 'exclude' filter.
-        """
-        for root, dirs, files in os.walk(where, followlinks=True):
-            # Copy dirs to iterate over it, then empty dirs.
-            all_dirs = dirs[:]
-            dirs[:] = []
-
-            for dir in all_dirs:
-                full_path = os.path.join(root, dir)
-                rel_path = os.path.relpath(full_path, where)
-                package = rel_path.replace(os.path.sep, '.')
-
-                # Skip directory trees that are not valid packages
-                if '.' in dir or not cls._looks_like_package(full_path):
-                    continue
-
-                # Should this package be included?
-                if include(package) and not exclude(package):
-                    yield package
-
-                # Keep searching subdirectories, as there may be more packages
-                # down there, even if the parent was excluded.
-                dirs.append(dir)
-
-    @staticmethod
-    def _looks_like_package(path):
-        """Does a directory look like a package?"""
-        return os.path.isfile(os.path.join(path, '__init__.py'))
-
-    @staticmethod
-    def _build_filter(*patterns):
-        """
-        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=pat) for pat in patterns)
-
-
-class PEP420PackageFinder(PackageFinder):
-    @staticmethod
-    def _looks_like_package(path):
-        return True
-
-
 find_packages = PackageFinder.find
 find_namespace_packages = PEP420PackageFinder.find
 

setuptools/discovery.py

@@ -0,0 +1,89 @@
+"""Automatic discovery for Python modules and packages for inclusion in the
+distribution.
+"""
+
+import os
+from fnmatch import fnmatchcase
+
+import _distutils_hack.override  # noqa: F401
+
+from distutils.util import convert_path
+
+
+class PackageFinder:
+    """
+    Generate a list of all Python packages found within a directory
+    """
+
+    @classmethod
+    def find(cls, where='.', exclude=(), include=('*',)):
+        """Return a list all Python packages found within directory 'where'
+
+        'where' is the root directory which will be searched for packages.  It
+        should be supplied as a "cross-platform" (i.e. URL-style) path; it will
+        be converted to the appropriate local path syntax.
+
+        'exclude' is a sequence of package names to exclude; '*' can be used
+        as a wildcard in the names, such that 'foo.*' will exclude all
+        subpackages of 'foo' (but not 'foo' itself).
+
+        'include' is a sequence of package names to include.  If it's
+        specified, only the named packages will be included.  If it's not
+        specified, all found packages will be included.  'include' can contain
+        shell style wildcard patterns just like 'exclude'.
+        """
+
+        return list(
+            cls._find_packages_iter(
+                convert_path(where),
+                cls._build_filter('ez_setup', '*__pycache__', *exclude),
+                cls._build_filter(*include),
+            )
+        )
+
+    @classmethod
+    def _find_packages_iter(cls, where, exclude, include):
+        """
+        All the packages found in 'where' that pass the 'include' filter, but
+        not the 'exclude' filter.
+        """
+        for root, dirs, files in os.walk(where, followlinks=True):
+            # Copy dirs to iterate over it, then empty dirs.
+            all_dirs = dirs[:]
+            dirs[:] = []
+
+            for dir in all_dirs:
+                full_path = os.path.join(root, dir)
+                rel_path = os.path.relpath(full_path, where)
+                package = rel_path.replace(os.path.sep, '.')
+
+                # Skip directory trees that are not valid packages
+                if '.' in dir or not cls._looks_like_package(full_path):
+                    continue
+
+                # Should this package be included?
+                if include(package) and not exclude(package):
+                    yield package
+
+                # Keep searching subdirectories, as there may be more packages
+                # down there, even if the parent was excluded.
+                dirs.append(dir)
+
+    @staticmethod
+    def _looks_like_package(path):
+        """Does a directory look like a package?"""
+        return os.path.isfile(os.path.join(path, '__init__.py'))
+
+    @staticmethod
+    def _build_filter(*patterns):
+        """
+        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=pat) for pat in patterns)
+
+
+class PEP420PackageFinder(PackageFinder):
+    @staticmethod
+    def _looks_like_package(path):
+        return True