Check for script shadowing stdlib

Author: hauntsaninja

Lib/test/test_import/__init__.py

@@ -790,6 +790,28 @@ def test_issue105979(self):
         self.assertIn("Frozen object named 'x' is invalid",
                       str(cm.exception))
 
+    def test_delete_sys_stdlib_module_names(self):
+        args = ["-c", "import sys; del sys.stdlib_module_names; sys.stdlib_module_names"]
+        popen = script_helper.spawn_python(*args)
+        stdout, stderr = popen.communicate()
+        self.assertIn(
+            b"AttributeError: module 'sys' has no attribute 'stdlib_module_names'",
+            stdout
+        )
+
+    def test_cwd_script_shadowing_stdlib(self):
+        with CleanImport('collections'):
+            import collections
+            collections.__spec__ = types.SimpleNamespace()
+            collections.__spec__.origin = os.path.join(os.getcwd(), 'collections.py')
+            with self.assertRaisesRegex(
+                AttributeError,
+                r"module 'collections' has no attribute 'does_not_exist' \(most "
+                r"likely due to '.*collections.py' shadowing the standard "
+                r"library module named 'collections'\)"
+            ):
+                collections.does_not_exist
+
 
 @skip_if_dont_write_bytecode
 class FilePermissionTests(unittest.TestCase):

Objects/moduleobject.c

@@ -848,39 +848,103 @@ _Py_module_getattro_impl(PyModuleObject *m, PyObject *name, int suppress)
         Py_DECREF(origin);
     }
 
-    int rc = _PyModuleSpec_IsInitializing(spec);
-    if (rc > 0) {
-        if (valid_origin == 1) {
-            PyErr_Format(PyExc_AttributeError,
-                        "partially initialized "
-                        "module '%U' from '%U' has no attribute '%U' "
-                        "(most likely due to a circular import)",
-                        mod_name, origin, name);
-        }
-        else {
-            PyErr_Format(PyExc_AttributeError,
-                        "partially initialized "
-                        "module '%U' has no attribute '%U' "
-                        "(most likely due to a circular import)",
-                        mod_name, name);
+    int is_script_shadowing_stdlib = 0;
+    // Check mod.__name__ in sys.stdlib_module_names
+    // and os.path.dirname(mod.__spec__.origin) == os.getcwd()
+    PyObject *stdlib = NULL;
+    if (valid_origin == 1) {
+        if (
+            // avoid bad recursion
+            PyUnicode_CompareWithASCIIString(mod_name, "sys") != 0
+            && PyUnicode_CompareWithASCIIString(mod_name, "os") != 0
+            && PyUnicode_CompareWithASCIIString(mod_name, "builtins") != 0
+        ) {
+            stdlib = _PyImport_GetModuleAttrString("sys", "stdlib_module_names");
+            if (!stdlib) {
+                goto done;
+            }
+            if (PySet_Contains(stdlib, mod_name)) {
+                PyObject *os_path = _PyImport_GetModuleAttrString("os", "path");
+                if (!os_path) {
+                    goto done;
+                }
+                PyObject *dirname = PyObject_GetAttrString(os_path, "dirname");
+                Py_DECREF(os_path);
+                if (!dirname) {
+                    goto done;
+                }
+                PyObject *origin_dir = _PyObject_CallOneArg(dirname, origin);
+                Py_DECREF(dirname);
+                if (!origin_dir) {
+                    goto done;
+                }
+
+                PyObject *getcwd = _PyImport_GetModuleAttrString("os", "getcwd");
+                if (!getcwd) {
+                    Py_DECREF(origin_dir);
+                    goto done;
+                }
+                PyObject *cwd = _PyObject_CallNoArgs(getcwd);
+                Py_DECREF(getcwd);
+                if (!cwd) {
+                    Py_DECREF(origin_dir);
+                    goto done;
+                }
+
+                is_script_shadowing_stdlib = PyObject_RichCompareBool(origin_dir, cwd, Py_EQ);
+                Py_DECREF(origin_dir);
+                Py_DECREF(cwd);
+                if (is_script_shadowing_stdlib < 0) {
+                    goto done;
+                }
+            }
         }
     }
-    else if (rc == 0) {
-        rc = _PyModuleSpec_IsUninitializedSubmodule(spec, name);
+
+    if (is_script_shadowing_stdlib == 1) {
+        PyErr_Format(PyExc_AttributeError,
+                    "module '%U' has no attribute '%U' "
+                    "(most likely due to '%U' shadowing the standard library "
+                    "module named '%U')",
+                    mod_name, name, origin, mod_name);
+    } else {
+        int rc = _PyModuleSpec_IsInitializing(spec);
         if (rc > 0) {
-            PyErr_Format(PyExc_AttributeError,
-                        "cannot access submodule '%U' of module '%U' "
-                        "(most likely due to a circular import)",
-                        name, mod_name);
+            if (valid_origin == 1) {
+                PyErr_Format(PyExc_AttributeError,
+                            "partially initialized "
+                            "module '%U' from '%U' has no attribute '%U' "
+                            "(most likely due to a circular import)",
+                            mod_name, origin, name);
+            }
+            else {
+                PyErr_Format(PyExc_AttributeError,
+                            "partially initialized "
+                            "module '%U' has no attribute '%U' "
+                            "(most likely due to a circular import)",
+                            mod_name, name);
+            }
         }
         else if (rc == 0) {
-            PyErr_Format(PyExc_AttributeError,
-                        "module '%U' has no attribute '%U'",
-                        mod_name, name);
+            rc = _PyModuleSpec_IsUninitializedSubmodule(spec, name);
+            if (rc > 0) {
+                PyErr_Format(PyExc_AttributeError,
+                            "cannot access submodule '%U' of module '%U' "
+                            "(most likely due to a circular import)",
+                            name, mod_name);
+            }
+            else if (rc == 0) {
+                PyErr_Format(PyExc_AttributeError,
+                            "module '%U' has no attribute '%U'",
+                            mod_name, name);
+            }
         }
     }
+
+done:
     Py_XDECREF(spec);
     Py_XDECREF(origin);
+    Py_XDECREF(stdlib);
     Py_DECREF(mod_name);
     return NULL;
 }