gh-69605: Check for already imported modules in PyREPL module completion

Lib/_pyrepl/_module_completer.py

@@ -107,7 +107,25 @@ def _find_modules(self, path: str, prefix: str) -> list[str]:
             if path is None:
                 return []
 
-        modules: Iterable[pkgutil.ModuleInfo] = self.global_cache
+        modules: Iterable[pkgutil.ModuleInfo]
+        imported_module = sys.modules.get(path.split('.')[0])
+        if imported_module:
+            # Module already imported: only look for its submodules,
+            # even if a module with the same name would be higher in path
+            imported_path = (imported_module.__spec__
+                             and imported_module.__spec__.origin)
+            if imported_path:
+                if os.path.basename(imported_path) == "__init__.py":  # package
+                    imported_path = os.path.dirname(imported_path)
+                import_location = os.path.dirname(imported_path)
+                modules = list(pkgutil.iter_modules([import_location]))
+            else:
+                # Module already imported but without spec/origin:
+                # propose no suggestions
+                modules = []
+        else:
+            modules = self.global_cache
+
         is_stdlib_import: bool | None = None
         for segment in path.split('.'):
             modules = [mod_info for mod_info in modules

Lib/test/test_pyrepl/test_pyrepl.py

@@ -1090,17 +1090,82 @@ def test_hardcoded_stdlib_submodules(self):
                 self.assertEqual(output, expected)
 
     def test_hardcoded_stdlib_submodules_not_proposed_if_local_import(self):
-        with tempfile.TemporaryDirectory() as _dir:
+        with (tempfile.TemporaryDirectory() as _dir,
+              patch.object(sys, "modules", {})):  # hide imported module
             dir = pathlib.Path(_dir)
             (dir / "collections").mkdir()
             (dir / "collections" / "__init__.py").touch()
             (dir / "collections" / "foo.py").touch()
-            with patch.object(sys, "path", [dir, *sys.path]):
+            with patch.object(sys, "path", [_dir, *sys.path]):
                 events = code_to_events("import collections.\t\n")
                 reader = self.prepare_reader(events, namespace={})
                 output = reader.readline()
                 self.assertEqual(output, "import collections.foo")
 
+    def test_already_imported_stdlib_module_no_other_suggestions(self):
+        with (tempfile.TemporaryDirectory() as _dir,
+              patch.object(sys, "path", [_dir, *sys.path])):
+            dir = pathlib.Path(_dir)
+            (dir / "collections").mkdir()
+            (dir / "collections" / "__init__.py").touch()
+            (dir / "collections" / "foo.py").touch()
+
+            # collections found in dir, but was already imported
+            # from stdlib at startup -> suggest stdlib submodules only
+            events = code_to_events("import collections.\t\n")
+            reader = self.prepare_reader(events, namespace={})
+            output = reader.readline()
+            self.assertEqual(output, "import collections.abc")
+
+    def test_already_imported_custom_module_no_other_suggestions(self):
+        with (tempfile.TemporaryDirectory() as _dir1,
+              tempfile.TemporaryDirectory() as _dir2,
+              patch.object(sys, "path", [_dir2, _dir1, *sys.path])):
+            dir1 = pathlib.Path(_dir1)
+            (dir1 / "mymodule").mkdir()
+            (dir1 / "mymodule" / "__init__.py").touch()
+            (dir1 / "mymodule" / "foo.py").touch()
+            importlib.import_module("mymodule")
+
+            dir2 = pathlib.Path(_dir2)
+            (dir2 / "mymodule").mkdir()
+            (dir2 / "mymodule" / "__init__.py").touch()
+            (dir2 / "mymodule" / "bar.py").touch()
+            # mymodule found in dir2 before dir1, but it was already imported
+            # from dir1 -> suggest dir1 submodules only
+            events = code_to_events("import mymodule.\t\n")
+            reader = self.prepare_reader(events, namespace={})
+            output = reader.readline()
+            self.assertEqual(output, "import mymodule.foo")
+
+            del sys.modules["mymodule"]
+            # mymodule not imported anymore -> suggest dir2 submodules
+            events = code_to_events("import mymodule.\t\n")
+            reader = self.prepare_reader(events, namespace={})
+            output = reader.readline()
+            self.assertEqual(output, "import mymodule.bar")
+
+    def test_already_imported_custom_file_no_suggestions(self):
+        # Same as before, but mymodule from dir1 has no submodules
+        # -> propose nothing
+        with (tempfile.TemporaryDirectory() as _dir1,
+              tempfile.TemporaryDirectory() as _dir2,
+              patch.object(sys, "path", [_dir2, _dir1, *sys.path])):
+            dir1 = pathlib.Path(_dir1)
+            (dir1 / "mymodule").mkdir()
+            (dir1 / "mymodule.py").touch()
+            importlib.import_module("mymodule")
+
+            dir2 = pathlib.Path(_dir2)
+            (dir2 / "mymodule").mkdir()
+            (dir2 / "mymodule" / "__init__.py").touch()
+            (dir2 / "mymodule" / "bar.py").touch()
+            events = code_to_events("import mymodule.\t\n")
+            reader = self.prepare_reader(events, namespace={})
+            output = reader.readline()
+            self.assertEqual(output, "import mymodule.")
+            del sys.modules["mymodule"]
+
     def test_get_path_and_prefix(self):
         cases = (
             ('', ('', '')),

Misc/NEWS.d/next/Core_and_Builtins/2025-09-30-21-59-56.gh-issue-69605.qcmGF3.rst

@@ -0,0 +1,2 @@
+Fix edge-cases around already imported modules in the :term:`REPL`
+auto-completion of imports.