From 7f1b23d57e7199a3f1cc826b4d94f0c66be3574d Mon Sep 17 00:00:00 2001
From: Anderson Bravalheri <andersonbravalheri@gmail.com>
Date: Fri, 10 Jun 2022 21:45:11 +0100
Subject: [PATCH 1/2] Add test capturing expectations

---
 distutils/tests/test_build_py.py | 42 ++++++++++++++++++++++++++++++++
 1 file changed, 42 insertions(+)

diff --git a/distutils/tests/test_build_py.py b/distutils/tests/test_build_py.py
index 4585d799..eb01d81a 100644
--- a/distutils/tests/test_build_py.py
+++ b/distutils/tests/test_build_py.py
@@ -7,6 +7,7 @@
 from distutils.command.build_py import build_py
 from distutils.core import Distribution
 from distutils.errors import DistutilsFileError
+from unittest.mock import patch
 
 from distutils.tests import support
 from test.support import run_unittest
@@ -167,6 +168,47 @@ def test_dont_write_bytecode(self):
 
         self.assertIn('byte-compiling is disabled', self.logs[0][1] % self.logs[0][2])
 
+    @patch("distutils.command.build_py.log.warn")
+    def test_namespace_package_does_not_warn(self, log_warn):
+        """
+        Originally distutils implementation did not account for PEP 420
+        and included warns for package directories that did not contain
+        ``__init__.py`` files.
+        After the acceptance of PEP 420, these warnings don't make more sense
+        so we want to ensure there are not displayed to not confuse the users.
+        """
+        # Create a fake project structure with a package namespace:
+        tmp = self.mkdtemp()
+        os.chdir(tmp)
+        os.makedirs("ns/pkg")
+        open("ns/pkg/module.py", "w").close()
+
+        # Set up a trap if the undesirable effect is observed:
+        def _trap(msg, *args):
+            if "package init file" in msg and "not found" in msg:
+                raise AssertionError(f"Undesired warning: {msg!r} {args!r}")
+
+        log_warn.side_effect = _trap
+
+        # Configure the package:
+        attrs = {
+            "name": "ns.pkg",
+            "packages": ["ns", "ns.pkg"],
+            "script_name": "setup.py",
+        }
+        dist = Distribution(attrs)
+
+        # Run code paths that would trigger the trap:
+        cmd = dist.get_command_obj("build_py")
+        cmd.finalize_options()
+        modules = cmd.find_all_modules()
+        assert len(modules) == 1
+        module_path = modules[0][-1]
+        assert module_path.replace(os.sep, "/") == "ns/pkg/module.py"
+
+        cmd.run()
+        # Test should complete successfully with no exception
+
 
 def test_suite():
     return unittest.TestLoader().loadTestsFromTestCase(BuildPyTestCase)

From 27350b0b0cf11313509160542f435bfe59782afa Mon Sep 17 00:00:00 2001
From: Anderson Bravalheri <andersonbravalheri@gmail.com>
Date: Fri, 10 Jun 2022 21:03:03 +0100
Subject: [PATCH 2/2] Remove warnings on namespace packages

---
 distutils/command/build_py.py | 7 +------
 1 file changed, 1 insertion(+), 6 deletions(-)

diff --git a/distutils/command/build_py.py b/distutils/command/build_py.py
index 1b22004e..7723d359 100644
--- a/distutils/command/build_py.py
+++ b/distutils/command/build_py.py
@@ -201,16 +201,11 @@ def check_package(self, package, package_dir):
                     "but is not a directory" % package_dir
                 )
 
-        # Require __init__.py for all but the "root package"
+        # Directories without __init__.py are namespace packages (PEP 420).
         if package:
             init_py = os.path.join(package_dir, "__init__.py")
             if os.path.isfile(init_py):
                 return init_py
-            else:
-                log.warn(
-                    ("package init file '%s' not found " + "(or not a regular file)"),
-                    init_py,
-                )
 
         # Either not in a package at all (__init__.py not expected), or
         # __init__.py doesn't exist -- so don't return the filename.