Remove dependency on pkg_resources from setuptools

astroid/interpreter/_import/spec.py

@@ -144,7 +144,7 @@ def contribute_to_path(self, spec, processed):
             # Builtin.
             return None
 
-        if _is_setuptools_namespace(spec.location):
+        if util._is_setuptools_namespace(spec.location):
             # extend_path is called, search sys.path for module/packages
             # of this name see pkgutil.extend_path documentation
             path = [
@@ -253,20 +253,6 @@ def contribute_to_path(self, spec, processed):
 )
 
 
-def _is_setuptools_namespace(location):
-    try:
-        with open(os.path.join(location, "__init__.py"), "rb") as stream:
-            data = stream.read(4096)
-    except OSError:
-        return None
-    else:
-        extend_path = b"pkgutil" in data and b"extend_path" in data
-        declare_namespace = (
-            b"pkg_resources" in data and b"declare_namespace(__name__)" in data
-        )
-        return extend_path or declare_namespace
-
-
 @lru_cache()
 def _cached_set_diff(left, right):
     result = set(left)

astroid/interpreter/_import/util.py

@@ -2,9 +2,25 @@
 # For details: https://github.com/PyCQA/astroid/blob/main/LICENSE
 # Copyright (c) https://github.com/PyCQA/astroid/blob/main/CONTRIBUTORS.txt
 
+import os
+import pathlib
 from importlib.util import _find_spec_from_path
 
 
+def _is_setuptools_namespace(location):
+    try:
+        with open(os.path.join(location, "__init__.py"), "rb") as stream:
+            data = stream.read(4096)
+    except OSError:
+        return None
+    else:
+        extend_path = b"pkgutil" in data and b"extend_path" in data
+        declare_namespace = (
+            b"pkg_resources" in data and b"declare_namespace(__name__)" in data
+        )
+        return extend_path or declare_namespace
+
+
 def is_namespace(modname: str) -> bool:
     found_spec = None
 
@@ -30,4 +46,13 @@ def is_namespace(modname: str) -> bool:
     if found_spec is None:
         return False
 
+    if found_spec.submodule_search_locations and any(
+        _is_setuptools_namespace(directory)
+        for directory in pathlib.Path(
+            found_spec.submodule_search_locations._path[0]
+        ).iterdir()
+        if directory.is_dir()
+    ):
+        return True
+
     return found_spec.origin == "namespace"

tests/unittest_manager.py

@@ -14,6 +14,7 @@
 from astroid import manager, test_utils
 from astroid.const import IS_JYTHON
 from astroid.exceptions import AstroidBuildingError, AstroidImportError
+from astroid.interpreter._import import util
 from astroid.nodes import Const
 
 from . import resources
@@ -107,6 +108,11 @@ def test_ast_from_namespace_pkgutil(self) -> None:
     def test_ast_from_namespace_pkg_resources(self) -> None:
         self._test_ast_from_old_namespace_package_protocol("pkg_resources")
 
+    def test_identify_old_namespace_package_protocol(self) -> None:
+        self.assertTrue(
+            util.is_namespace("tests.testdata.python3.data.path_pkg_resources_1")
+        )
+
     def test_implicit_namespace_package(self) -> None:
         data_dir = os.path.dirname(resources.find("data/namespace_pep_420"))
         contribute = os.path.join(data_dir, "contribute_to_namespace")