Remove dependency on pkg_resources from setuptools

ChangeLog

@@ -13,6 +13,10 @@ Release date: TBA
 
   Closes #1512
 
+* Remove dependency on ``pkg_resources`` from ``setuptools``.
+
+  Closes #1103
+
 * Rename ``ModuleSpec`` -> ``module_type`` constructor parameter to match attribute
   name and improve typing. Use ``type`` instead.
 

astroid/interpreter/_import/spec.py

@@ -171,7 +171,7 @@ def contribute_to_path(self, spec, processed):
 
 
 class ExplicitNamespacePackageFinder(ImportlibFinder):
-    """A finder for the explicit namespace packages, generated through pkg_resources."""
+    """A finder for the explicit namespace packages."""
 
     def find_module(self, modname, module_parts, processed, submodule_path):
         if processed:

astroid/interpreter/_import/util.py

@@ -2,15 +2,32 @@
 # For details: https://github.com/PyCQA/astroid/blob/main/LICENSE
 # Copyright (c) https://github.com/PyCQA/astroid/blob/main/CONTRIBUTORS.txt
 
-try:
-    import pkg_resources
-except ImportError:
-    pkg_resources = None  # type: ignore[assignment]
+from importlib.util import _find_spec_from_path
 
 
-def is_namespace(modname):
-    return (
-        pkg_resources is not None
-        and hasattr(pkg_resources, "_namespace_packages")
-        and modname in pkg_resources._namespace_packages
-    )
+def is_namespace(modname: str) -> bool:
+    found_spec = None
+
+    # find_spec() attempts to import parent packages when given dotted paths.
+    # That's unacceptable here, so we fallback to _find_spec_from_path(), which does
+    # not, but requires instead that each single parent ('astroid', 'nodes', etc.)
+    # be specced from left to right.
+    working_modname = ""
+    last_parent = None
+    for component in modname.split("."):
+        if working_modname:
+            working_modname += "." + component
+        else:
+            # First component
+            working_modname = component
+        try:
+            found_spec = _find_spec_from_path(working_modname, last_parent)
+        except ValueError:
+            # executed .pth files may not have __spec__
+            return True
+        last_parent = working_modname
+
+    if found_spec is None:
+        return False
+
+    return found_spec.origin == "namespace"

setup.cfg

@@ -40,7 +40,6 @@ packages = find:
 install_requires =
     lazy_object_proxy>=1.4.0
     wrapt>=1.11,<2
-    setuptools>=20.0
     typed-ast>=1.4.0,<2.0;implementation_name=="cpython" and python_version<"3.8"
     typing-extensions>=3.10;python_version<"3.10"
 python_requires = >=3.6.2

tests/unittest_manager.py

@@ -10,8 +10,6 @@
 from contextlib import contextmanager
 from typing import Iterator
 
-import pkg_resources
-
 import astroid
 from astroid import manager, test_utils
 from astroid.const import IS_JYTHON
@@ -128,7 +126,6 @@ def test_implicit_namespace_package(self) -> None:
     def test_namespace_package_pth_support(self) -> None:
         pth = "foogle_fax-0.12.5-py2.7-nspkg.pth"
         site.addpackage(resources.RESOURCE_PATH, pth, [])
-        pkg_resources._namespace_packages["foogle"] = []
 
         try:
             module = self.manager.ast_from_module_name("foogle.fax")
@@ -138,18 +135,14 @@ def test_namespace_package_pth_support(self) -> None:
             with self.assertRaises(AstroidImportError):
                 self.manager.ast_from_module_name("foogle.moogle")
         finally:
-            del pkg_resources._namespace_packages["foogle"]
             sys.modules.pop("foogle")
 
     def test_nested_namespace_import(self) -> None:
         pth = "foogle_fax-0.12.5-py2.7-nspkg.pth"
         site.addpackage(resources.RESOURCE_PATH, pth, [])
-        pkg_resources._namespace_packages["foogle"] = ["foogle.crank"]
-        pkg_resources._namespace_packages["foogle.crank"] = []
         try:
             self.manager.ast_from_module_name("foogle.crank")
         finally:
-            del pkg_resources._namespace_packages["foogle"]
             sys.modules.pop("foogle")
 
     def test_namespace_and_file_mismatch(self) -> None:
@@ -158,12 +151,10 @@ def test_namespace_and_file_mismatch(self) -> None:
         self.assertEqual(ast.name, "unittest")
         pth = "foogle_fax-0.12.5-py2.7-nspkg.pth"
         site.addpackage(resources.RESOURCE_PATH, pth, [])
-        pkg_resources._namespace_packages["foogle"] = []
         try:
             with self.assertRaises(AstroidImportError):
                 self.manager.ast_from_module_name("unittest.foogle.fax")
         finally:
-            del pkg_resources._namespace_packages["foogle"]
             sys.modules.pop("foogle")
 
     def _test_ast_from_zip(self, archive: str) -> None: