bpo-42134: Raise ImportWarning when calling find_module() in the import system (GH-25044)

4 files changed, 20 insertions, 6 deletions

diff --git a/Lib/importlib/_bootstrap.py b/Lib/importlib/_bootstrap.py
index d5acb65..ab52e77 100644
--- a/Lib/importlib/_bootstrap.py
+++ b/Lib/importlib/_bootstrap.py
@@ -903,8 +903,9 @@ def _resolve_name(name, package, level):
 
 
 def _find_spec_legacy(finder, name, path):
-    # This would be a good place for a DeprecationWarning if
-    # we ended up going that route.
+    msg = (f"{_object_name(finder)}.find_spec() not found; "
+                           "falling back to find_module()")
+    _warnings.warn(msg, ImportWarning)
     loader = finder.find_module(name, path)
     if loader is None:
         return None
diff --git a/Lib/importlib/_bootstrap_external.py b/Lib/importlib/_bootstrap_external.py
index dac881f..bf7c268 100644
--- a/Lib/importlib/_bootstrap_external.py
+++ b/Lib/importlib/_bootstrap_external.py
@@ -1324,6 +1324,9 @@ class PathFinder:
         if hasattr(finder, 'find_loader'):
             loader, portions = finder.find_loader(fullname)
         else:
+            msg = (f"{_bootstrap._object_name(finder)}.find_spec() not found; "
+                           "falling back to find_module()")
+            _warnings.warn(msg, ImportWarning)
             loader = finder.find_module(fullname)
             portions = []
         if loader is not None:
diff --git a/Lib/test/test_importlib/import_/test_path.py b/Lib/test/test_importlib/import_/test_path.py
index 18c81dd..c51aee2 100644
--- a/Lib/test/test_importlib/import_/test_path.py
+++ b/Lib/test/test_importlib/import_/test_path.py
@@ -123,12 +123,16 @@ class FinderTests:
         failing_finder.to_return = None
         path = 'testing path'
         with util.import_state(path_importer_cache={path: failing_finder}):
-            self.assertIsNone(
+            with warnings.catch_warnings():
+                warnings.simplefilter("ignore", ImportWarning)
+                self.assertIsNone(
                     self.machinery.PathFinder.find_spec('whatever', [path]))
         success_finder = TestFinder()
         success_finder.to_return = __loader__
         with util.import_state(path_importer_cache={path: success_finder}):
-            spec = self.machinery.PathFinder.find_spec('whatever', [path])
+            with warnings.catch_warnings():
+                warnings.simplefilter("ignore", ImportWarning)
+                spec = self.machinery.PathFinder.find_spec('whatever', [path])
         self.assertEqual(spec.loader, __loader__)
 
     def test_finder_with_find_loader(self):
@@ -248,7 +252,9 @@ class PathEntryFinderTests:
 
         with util.import_state(path=[Finder.path_location]+sys.path[:],
                                path_hooks=[Finder]):
-            self.machinery.PathFinder.find_spec('importlib')
+            with warnings.catch_warnings():
+                warnings.simplefilter("ignore", ImportWarning)
+                self.machinery.PathFinder.find_spec('importlib')
 
     def test_finder_with_failing_find_module(self):
         # PathEntryFinder with find_module() defined should work.
@@ -266,7 +272,9 @@ class PathEntryFinderTests:
 
         with util.import_state(path=[Finder.path_location]+sys.path[:],
                                path_hooks=[Finder]):
-            self.machinery.PathFinder.find_module('importlib')
+            with warnings.catch_warnings():
+                warnings.simplefilter("ignore", ImportWarning)
+                self.machinery.PathFinder.find_module('importlib')
 
 
 (Frozen_PEFTests,
diff --git a/Lib/test/test_importlib/test_api.py b/Lib/test/test_importlib/test_api.py
index 3f06a10..384ae9c 100644
--- a/Lib/test/test_importlib/test_api.py
+++ b/Lib/test/test_importlib/test_api.py
@@ -151,6 +151,7 @@ class FindLoaderTests:
             with test_util.import_state(meta_path=[self.FakeMetaFinder]):
                 with warnings.catch_warnings():
                     warnings.simplefilter('ignore', DeprecationWarning)
+                    warnings.simplefilter('ignore', ImportWarning)
                     self.assertEqual((name, None), self.init.find_loader(name))
 
     def test_success_path(self):
@@ -161,6 +162,7 @@ class FindLoaderTests:
             with test_util.import_state(meta_path=[self.FakeMetaFinder]):
                 with warnings.catch_warnings():
                     warnings.simplefilter('ignore', DeprecationWarning)
+                    warnings.simplefilter('ignore', ImportWarning)
                     self.assertEqual((name, path),
                                      self.init.find_loader(name, path))