From 82d1fadebb6eafca23cf979f9fe7bf6e60ad9b7f Mon Sep 17 00:00:00 2001
From: MWR27 <64335495+MWR27@users.noreply.github.com>
Date: Wed, 3 Jun 2026 12:32:11 -0400
Subject: [PATCH 1/5] Add warning for implicit relative imports

---
 Python/import.c | 41 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 41 insertions(+)

diff --git a/Python/import.c b/Python/import.c
index b79354b37a40645..1262a1c2b6c9f46 100644
--- a/Python/import.c
+++ b/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]; /* maybe rename to pkgstr or pkgname? */
+    char *orig_name = name;
+    int is_from_form;
+    int might_warn_implicit;
+
     if (strchr(name, '/') != NULL
 #ifdef MS_WINDOWS
         || strchr(name, '\\') != NULL
@@ -2265,6 +2270,13 @@ import_module_level(char *name, PyObject *globals, PyObject *locals,
     if (parent == NULL)
         goto error_exit;
 
+    might_warn_implicit = level < 0 &&
+                          parent != Py_None &&
+                          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 +2315,35 @@ 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) {

From 411eee548d121bb82476decd8377c33ad1f16fff Mon Sep 17 00:00:00 2001
From: MWR27 <64335495+MWR27@users.noreply.github.com>
Date: Wed, 3 Jun 2026 13:09:33 -0400
Subject: [PATCH 2/5] Fix not recognizing submodules in multiple levels of
 subpackages

---
 Python/import.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/Python/import.c b/Python/import.c
index 1262a1c2b6c9f46..9b8759164d00cb4 100644
--- a/Python/import.c
+++ b/Python/import.c
@@ -2272,6 +2272,7 @@ import_module_level(char *name, PyObject *globals, PyObject *locals,
 
     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);

From 1bbc51aa12c78e697f84f2e1b3dc7b08639342c1 Mon Sep 17 00:00:00 2001
From: MWR27 <64335495+MWR27@users.noreply.github.com>
Date: Tue, 9 Jun 2026 18:20:35 -0400
Subject: [PATCH 3/5] Add tests

---
 Lib/test/test_py3kwarn.py | 54 +++++++++++++++++++++++++++++++++++++--
 1 file changed, 52 insertions(+), 2 deletions(-)

diff --git a/Lib/test/test_py3kwarn.py b/Lib/test/test_py3kwarn.py
index 0aa981089606775..c2963f1317a7bf8 100644
--- a/Lib/test/test_py3kwarn.py
+++ b/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(str(warning.message) + ': ' + str(warning.fix), 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)):

From 09ddb475bb327c780777552b26e84c2a050bf675 Mon Sep 17 00:00:00 2001
From: MWR27 <64335495+MWR27@users.noreply.github.com>
Date: Wed, 10 Jun 2026 11:23:19 -0400
Subject: [PATCH 4/5] Implement suggested changes

---
 Lib/test/test_py3kwarn.py | 2 +-
 Python/import.c           | 4 ++--
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/Lib/test/test_py3kwarn.py b/Lib/test/test_py3kwarn.py
index c2963f1317a7bf8..7b2d624b0b523f7 100644
--- a/Lib/test/test_py3kwarn.py
+++ b/Lib/test/test_py3kwarn.py
@@ -63,7 +63,7 @@ def assertNoWarning(self, _, recorder):
 
     def assertWarningWithFix(self, _, warning, expected_msg, expected_fix):
         self.assertTrue(hasattr(warning, 'fix'))
-        self.assertEqual(str(warning.message) + ': ' + str(warning.fix), expected_msg + ': ' + expected_fix)
+        self.assertEqual('{}: {}'.format(warning.message, warning.fix), '{}: {}'.format(warning.message, warning.fix))
 
     def test_implicit_relative_import(self):
         expected_msg = ("implicit relative import 'importee' resolved to 'testpkg.subpkg.importee'; "
diff --git a/Python/import.c b/Python/import.c
index 9b8759164d00cb4..7f6731952e6760c 100644
--- a/Python/import.c
+++ b/Python/import.c
@@ -2247,9 +2247,9 @@ import_module_level(char *name, PyObject *globals, PyObject *locals,
     Py_ssize_t buflen = 0;
     PyObject *parent, *head, *next, *tail;
 
-    char parentstr[MAXPATHLEN + 1]; /* maybe rename to pkgstr or pkgname? */
+    char parentstr[MAXPATHLEN + 1];
     char *orig_name = name;
-    int is_from_form;
+    int is_from_form = 0;
     int might_warn_implicit;
 
     if (strchr(name, '/') != NULL

From d8022d9347b27c0c636745e8857896d2bffc77fe Mon Sep 17 00:00:00 2001
From: MWR27 <64335495+MWR27@users.noreply.github.com>
Date: Wed, 10 Jun 2026 11:26:36 -0400
Subject: [PATCH 5/5] assertWarningWithFix hotfix

---
 Lib/test/test_py3kwarn.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Lib/test/test_py3kwarn.py b/Lib/test/test_py3kwarn.py
index 7b2d624b0b523f7..a7b5a6ee8ca78ec 100644
--- a/Lib/test/test_py3kwarn.py
+++ b/Lib/test/test_py3kwarn.py
@@ -63,7 +63,7 @@ def assertNoWarning(self, _, recorder):
 
     def assertWarningWithFix(self, _, warning, expected_msg, expected_fix):
         self.assertTrue(hasattr(warning, 'fix'))
-        self.assertEqual('{}: {}'.format(warning.message, warning.fix), '{}: {}'.format(warning.message, 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'; "