Fixed #34952 -- Copied dir list when processing locale folders to avoid missing entries during os.walk traversal.

Co-authored-by: Natalia <124304+nessita@users.noreply.github.com>

2 files changed, 60 insertions, 1 deletions

diff --git a/django/core/management/commands/compilemessages.py b/django/core/management/commands/compilemessages.py
index 9ed3ef7c31..eddf31b794 100644
--- a/django/core/management/commands/compilemessages.py
+++ b/django/core/management/commands/compilemessages.py
@@ -91,7 +91,8 @@ class Command(BaseCommand):
 
         # Walk entire tree, looking for locale directories
         for dirpath, dirnames, filenames in os.walk(".", topdown=True):
-            for dirname in dirnames:
+            # As we may modify dirnames, iterate through a copy of it instead
+            for dirname in list(dirnames):
                 if is_ignored_path(
                     os.path.normpath(os.path.join(dirpath, dirname)), ignore_patterns
                 ):
diff --git a/tests/i18n/test_compilation.py b/tests/i18n/test_compilation.py
index ab74927c40..7da95ba9e9 100644
--- a/tests/i18n/test_compilation.py
+++ b/tests/i18n/test_compilation.py
@@ -195,6 +195,64 @@ class IgnoreDirectoryCompilationTests(MessageCompilationTests):
         self.assertNoneExist(self.CACHE_DIR, ["en", "fr", "it"])
         self.assertNoneExist(self.NESTED_DIR, ["en", "fr", "it"])
 
+    def test_no_dirs_accidentally_skipped(self):
+        os_walk_results = [
+            # To discover .po filepaths, compilemessages uses with a starting list of
+            # basedirs to inspect, which in this scenario are:
+            #   ["conf/locale", "locale"]
+            # Then os.walk is used to discover other locale dirs, ignoring dirs matching
+            # `ignore_patterns`. Mock the results to place an ignored directory directly
+            # before and after a directory named "locale".
+            [("somedir", ["ignore", "locale", "ignore"], [])],
+            # This will result in three basedirs discovered:
+            #   ["conf/locale", "locale", "somedir/locale"]
+            # os.walk is called for each locale in each basedir looking for .po files.
+            # In this scenario, we need to mock os.walk results for "en", "fr", and "it"
+            # locales for each basedir:
+            [("exclude/locale/LC_MESSAGES", [], ["en.po"])],
+            [("exclude/locale/LC_MESSAGES", [], ["fr.po"])],
+            [("exclude/locale/LC_MESSAGES", [], ["it.po"])],
+            [("exclude/conf/locale/LC_MESSAGES", [], ["en.po"])],
+            [("exclude/conf/locale/LC_MESSAGES", [], ["fr.po"])],
+            [("exclude/conf/locale/LC_MESSAGES", [], ["it.po"])],
+            [("exclude/somedir/locale/LC_MESSAGES", [], ["en.po"])],
+            [("exclude/somedir/locale/LC_MESSAGES", [], ["fr.po"])],
+            [("exclude/somedir/locale/LC_MESSAGES", [], ["it.po"])],
+        ]
+
+        module_path = "django.core.management.commands.compilemessages"
+        with mock.patch(f"{module_path}.os.walk", side_effect=os_walk_results):
+            with mock.patch(f"{module_path}.os.path.isdir", return_value=True):
+                with mock.patch(
+                    f"{module_path}.Command.compile_messages"
+                ) as mock_compile_messages:
+                    call_command("compilemessages", ignore=["ignore"], verbosity=4)
+
+        expected = [
+            (
+                [
+                    ("exclude/locale/LC_MESSAGES", "en.po"),
+                    ("exclude/locale/LC_MESSAGES", "fr.po"),
+                    ("exclude/locale/LC_MESSAGES", "it.po"),
+                ],
+            ),
+            (
+                [
+                    ("exclude/conf/locale/LC_MESSAGES", "en.po"),
+                    ("exclude/conf/locale/LC_MESSAGES", "fr.po"),
+                    ("exclude/conf/locale/LC_MESSAGES", "it.po"),
+                ],
+            ),
+            (
+                [
+                    ("exclude/somedir/locale/LC_MESSAGES", "en.po"),
+                    ("exclude/somedir/locale/LC_MESSAGES", "fr.po"),
+                    ("exclude/somedir/locale/LC_MESSAGES", "it.po"),
+                ],
+            ),
+        ]
+        self.assertEqual([c.args for c in mock_compile_messages.mock_calls], expected)
+
 
 class CompilationErrorHandling(MessageCompilationTests):
     def test_error_reported_by_msgfmt(self):