Implicit relative

Lib/test/test_py3kwarn.py

@@ -1,11 +1,11 @@
 import unittest
 import sys
+import os
 import contextlib
 from test.test_support import check_py3k_warnings, CleanImport, run_unittest
-from test.script_helper import assert_python_ok
 import warnings
 import base64
-from test import test_support
+from test import support, test_support, script_helper
 
 if not sys.py3kwarning:
     raise unittest.SkipTest('%s must be run with the -3 flag' % __name__)
@@ -61,6 +61,56 @@ def assertWarning(self, _, warning, expected_message):
     def assertNoWarning(self, _, recorder):
         self.assertEqual(len(recorder.warnings), 0)
 
+    def assertWarningWithFix(self, _, warning, expected_msg, expected_fix):
+        self.assertTrue(hasattr(warning, 'fix'))
+        self.assertEqual('{}: {}'.format(warning.message, warning.fix), '{}: {}'.format(expected_msg, expected_fix))
+
+    def test_implicit_relative_import(self):
+        expected_msg = ("implicit relative import 'importee' resolved to 'testpkg.subpkg.importee'; "
+                        "in 3.x imports are absolute by default, so this may resolve differently")
+        expected_fix = "use 'import testpkg.subpkg.importee' if the parent package is intended"
+        with self.check_py3k_warnings_with_fix() as w, test_support.temp_dir() as test_dir:
+            try:
+                sys.path.append(test_dir)
+
+                pkg_dir = os.path.join(test_dir, 'testpkg')
+                subpkg_dir = os.path.join(pkg_dir, 'subpkg')
+                script_helper.make_pkg(pkg_dir)
+                script_helper.make_pkg(subpkg_dir)
+                script_helper.make_script(subpkg_dir, 'importee', '')
+                script_helper.make_script(subpkg_dir, 'importer', 'import importee')
+
+                import testpkg.subpkg.importer
+                self.assertWarningWithFix(None, w, expected_msg, expected_fix)
+            finally:
+                sys.path.remove(test_dir)
+
+    def test_implicit_relative_import_from(self):
+        expected_msg = ("implicit relative import from 'importee' resolved to 'testpkg2.subpkg.importee'; "
+                        "in 3.x imports are absolute by default, so this may resolve differently")
+        expected_fix = "use 'from testpkg2.subpkg.importee import ...' if the parent package is intended"
+        with self.check_py3k_warnings_with_fix() as w, test_support.temp_dir() as test_dir:
+            try:
+                sys.path.append(test_dir)
+
+                pkg_dir = os.path.join(test_dir, 'testpkg2')
+                subpkg_dir = os.path.join(pkg_dir, 'subpkg')
+                script_helper.make_pkg(pkg_dir)
+                script_helper.make_pkg(subpkg_dir)
+                script_helper.make_script(subpkg_dir, 'importee', 'foo = 0')
+                script_helper.make_script(subpkg_dir, 'importer', 'from importee import foo')
+
+                import testpkg2.subpkg.importer
+                self.assertWarningWithFix(None, w, expected_msg, expected_fix)
+            finally:
+                sys.path.remove(test_dir)
+
+    def test_absolute_import_no_warning(self):
+        pass
+
+    def test_absolute_import_from_no_warning(self):
+        pass
+
     def test_backquote(self):
         expected = 'backquote not supported in 3.x; use repr()'
         with check_py3k_warnings((expected, SyntaxWarning)):

Python/import.c

@@ -2247,6 +2247,11 @@ import_module_level(char *name, PyObject *globals, PyObject *locals,
     Py_ssize_t buflen = 0;
     PyObject *parent, *head, *next, *tail;
 
+    char parentstr[MAXPATHLEN + 1];
+    char *orig_name = name;
+    int is_from_form = 0;
+    int might_warn_implicit;
+
     if (strchr(name, '/') != NULL
 #ifdef MS_WINDOWS
         || strchr(name, '\\') != NULL
@@ -2265,6 +2270,14 @@ import_module_level(char *name, PyObject *globals, PyObject *locals,
     if (parent == NULL)
         goto error_exit;
 
+    might_warn_implicit = level < 0 &&
+                          parent != Py_None &&
+                          strchr(name, '.') == NULL &&
+                          buflen + strlen(name) + 1 <= MAXPATHLEN;
+    if (might_warn_implicit) {
+        memcpy(parentstr, buf, buflen + 1);
+    }
+
     Py_INCREF(parent);
     head = load_next(parent, level < 0 ? Py_None : parent, &name, buf,
                         &buflen);
@@ -2303,6 +2316,35 @@ import_module_level(char *name, PyObject *globals, PyObject *locals,
         }
         if (!b)
             fromlist = NULL;
+        is_from_form = b;
+    }
+
+    if (might_warn_implicit) {
+        char potential_resolved[MAXPATHLEN + 2];
+        sprintf(potential_resolved, "%s.%s", parentstr, orig_name);
+
+        if (strcmp(potential_resolved, buf) == 0) {
+            char msg[524];
+            char fix[260];
+            if (is_from_form) {
+                sprintf(msg,
+                    "implicit relative import from '%.200s' resolved to '%.200s'; "
+                    "in 3.x imports are absolute by default, so this may resolve differently",
+                    orig_name, buf);
+                sprintf(fix,
+                    "use 'from %.200s import ...' if the parent package is intended", buf);
+            } else {
+                sprintf(msg,
+                    "implicit relative import '%.200s' resolved to '%.200s'; "
+                    "in 3.x imports are absolute by default, so this may resolve differently",
+                    orig_name, buf);
+                sprintf(fix,
+                    "use 'import %.200s' if the parent package is intended", buf);
+            }
+            if (PyErr_WarnPy3k_WithFix(msg, fix, 1) < 0) {
+                goto error_exit;
+            }
+        }
     }
 
     if (fromlist == NULL) {