bpo-37069: regrtest uses sys.unraisablehook (GH-13759)

regrtest now uses sys.unraisablehook() to mark a test as "environment
altered" (ENV_CHANGED) if it emits an "unraisable exception".
Moreover, regrtest logs a warning in this case.

Use "python3 -m test --fail-env-changed" to catch unraisable
exceptions in tests.

1 files changed, 29 insertions, 1 deletions

diff --git a/Lib/test/test_regrtest.py b/Lib/test/test_regrtest.py
index b616e89..904b326 100644
--- a/Lib/test/test_regrtest.py
+++ b/Lib/test/test_regrtest.py
@@ -499,7 +499,7 @@ class BaseTestCase(unittest.TestCase):
         if not input:
             input = ''
         if 'stderr' not in kw:
-            kw['stderr'] = subprocess.PIPE
+            kw['stderr'] = subprocess.STDOUT
         proc = subprocess.run(args,
                               universal_newlines=True,
                               input=input,
@@ -1124,6 +1124,34 @@ class ArgsTestCase(BaseTestCase):
                                   env_changed=[testname],
                                   fail_env_changed=True)
 
+    def test_unraisable_exc(self):
+        # --fail-env-changed must catch unraisable exception
+        code = textwrap.dedent(r"""
+            import unittest
+            import weakref
+
+            class MyObject:
+                pass
+
+            def weakref_callback(obj):
+                raise Exception("weakref callback bug")
+
+            class Tests(unittest.TestCase):
+                def test_unraisable_exc(self):
+                    obj = MyObject()
+                    ref = weakref.ref(obj, weakref_callback)
+                    # call weakref_callback() which logs
+                    # an unraisable exception
+                    obj = None
+        """)
+        testname = self.create_test(code=code)
+
+        output = self.run_tests("--fail-env-changed", "-v", testname, exitcode=3)
+        self.check_executed_tests(output, [testname],
+                                  env_changed=[testname],
+                                  fail_env_changed=True)
+        self.assertIn("Warning -- Unraisable exception", output)
+
 
 class TestUtils(unittest.TestCase):
     def test_format_duration(self):