From bcfc72aec4f86b3b4ae7aa161a6353403e4fc6d7 Mon Sep 17 00:00:00 2001
From: nightcityblade <nightcityblade@gmail.com>
Date: Sun, 11 Oct 2026 00:51:19 +0800
Subject: [PATCH] Fix discovery beside same-named namespace directories

---
 mypy/find_sources.py           | 12 ++++++++----
 mypy/test/test_find_sources.py | 12 ++++++++++++
 2 files changed, 20 insertions(+), 4 deletions(-)

diff --git a/mypy/find_sources.py b/mypy/find_sources.py
index e1edebe90985b..5afedbb1099a1 100644
--- a/mypy/find_sources.py
+++ b/mypy/find_sources.py
@@ -110,7 +110,7 @@ def is_explicit_package_base(self, path: str) -> bool:
     def find_sources_in_dir(self, path: str) -> list[BuildSource]:
         sources = []
 
-        seen: set[str] = set()
+        seen_file_stems: set[str] = set()
         names = sorted(self.fscache.listdir(path), key=keyfunc)
         for name in names:
             # Skip certain names altogether
@@ -128,12 +128,16 @@ def find_sources_in_dir(self, path: str) -> list[BuildSource]:
             if self.fscache.isdir(subpath):
                 sub_sources = self.find_sources_in_dir(subpath)
                 if sub_sources:
-                    seen.add(name)
+                    if any(
+                        self.fscache.isfile(os.path.join(subpath, "__init__" + suffix))
+                        for suffix in PY_EXTENSIONS
+                    ):
+                        seen_file_stems.add(name)
                     sources.extend(sub_sources)
             else:
                 stem, suffix = os.path.splitext(name)
-                if stem not in seen and suffix in PY_EXTENSIONS:
-                    seen.add(stem)
+                if stem not in seen_file_stems and suffix in PY_EXTENSIONS:
+                    seen_file_stems.add(stem)
                     module, base_dir = self.crawl_up(subpath)
                     sources.append(BuildSource(subpath, module, None, base_dir))
 
diff --git a/mypy/test/test_find_sources.py b/mypy/test/test_find_sources.py
index 321f3405e9991..b8eddec884d42 100644
--- a/mypy/test/test_find_sources.py
+++ b/mypy/test/test_find_sources.py
@@ -220,6 +220,18 @@ def test_find_sources_in_dir_namespace(self) -> None:
             ("f", "/pkg/a1/b"),
         ]
 
+    def test_find_sources_in_same_named_file_and_namespace_dir(self) -> None:
+        options = Options()
+        finder = SourceFinder(FakeFSCache({"/pkg/x.py", "/pkg/x/y.py"}), options)
+
+        assert find_sources_in_dir(finder, "/pkg") == [("x", "/pkg"), ("y", "/pkg/x")]
+
+    def test_find_sources_in_same_named_file_and_package_dir(self) -> None:
+        options = Options()
+        finder = SourceFinder(FakeFSCache({"/pkg/x.py", "/pkg/x/__init__.py"}), options)
+
+        assert find_sources_in_dir(finder, "/pkg") == [("x", "/pkg")]
+
     def test_find_sources_in_dir_namespace_explicit_base(self) -> None:
         options = Options()
         options.namespace_packages = True