bpo-41031: Match C and Python code formatting of unprintable exceptions and exceptions in the __main__ module. (GH-28139)

1 files changed, 29 insertions, 3 deletions

diff --git a/Lib/test/test_traceback.py b/Lib/test/test_traceback.py
index 949adef..363165d 100644
--- a/Lib/test/test_traceback.py
+++ b/Lib/test/test_traceback.py
@@ -172,7 +172,7 @@ class TracebackCases(unittest.TestCase):
                 1/0
         err = traceback.format_exception_only(X, X())
         self.assertEqual(len(err), 1)
-        str_value = '<unprintable %s object>' % X.__name__
+        str_value = '<exception str() failed>'
         if X.__module__ in ('__main__', 'builtins'):
             str_name = X.__qualname__
         else:
@@ -1171,19 +1171,45 @@ class BaseExceptionReportingTests:
                 exp = "\n".join(expected)
                 self.assertEqual(exp, err)
 
-    def test_format_exception_only_qualname(self):
+    def test_exception_qualname(self):
         class A:
             class B:
                 class X(Exception):
                     def __str__(self):
                         return "I am X"
-                    pass
+
         err = self.get_report(A.B.X())
         str_value = 'I am X'
         str_name = '.'.join([A.B.X.__module__, A.B.X.__qualname__])
         exp = "%s: %s\n" % (str_name, str_value)
         self.assertEqual(exp, err)
 
+    def test_exception_modulename(self):
+        class X(Exception):
+            def __str__(self):
+                return "I am X"
+
+        for modulename in '__main__', 'builtins', 'some_module':
+            X.__module__ = modulename
+            with self.subTest(modulename=modulename):
+                err = self.get_report(X())
+                str_value = 'I am X'
+                if modulename in ['builtins', '__main__']:
+                    str_name = X.__qualname__
+                else:
+                    str_name = '.'.join([X.__module__, X.__qualname__])
+                exp = "%s: %s\n" % (str_name, str_value)
+                self.assertEqual(exp, err)
+
+    def test_exception_bad__str__(self):
+        class X(Exception):
+            def __str__(self):
+                1/0
+        err = self.get_report(X())
+        str_value = '<exception str() failed>'
+        str_name = '.'.join([X.__module__, X.__qualname__])
+        self.assertEqual(err, f"{str_name}: {str_value}\n")
+
 
 class PyExcReportingTests(BaseExceptionReportingTests, unittest.TestCase):
     #