[3.9] bpo-42474: test TracebackException comparison to non-equal instances (GH-23557)

Lib/test/test_traceback.py

@@ -1103,7 +1103,7 @@ class TestTracebackException(unittest.TestCase):
         self.assertEqual(exc_info[0], exc.exc_type)
         self.assertEqual(str(exc_info[1]), str(exc))
 
-    def test_comparison(self):
+    def test_comparison_basic(self):
         try:
             1/0
         except Exception:
@@ -1115,6 +1115,43 @@ class TestTracebackException(unittest.TestCase):
         self.assertNotEqual(exc, object())
         self.assertEqual(exc, ALWAYS_EQ)
 
+    def test_comparison_params_variations(self):
+        def raise_exc():
+            try:
+                raise ValueError('bad value')
+            except:
+                raise
+
+        def raise_with_locals():
+            x, y = 1, 2
+            raise_exc()
+
+        try:
+            raise_with_locals()
+        except Exception:
+            exc_info = sys.exc_info()
+
+        exc = traceback.TracebackException(*exc_info)
+        exc1 = traceback.TracebackException(*exc_info, limit=10)
+        exc2 = traceback.TracebackException(*exc_info, limit=2)
+
+        self.assertEqual(exc, exc1)      # limit=10 gets all frames
+        self.assertNotEqual(exc, exc2)   # limit=2 truncates the output
+
+        # locals change the output
+        exc3 = traceback.TracebackException(*exc_info, capture_locals=True)
+        self.assertNotEqual(exc, exc3)
+
+        # there are no locals in the innermost frame
+        exc4 = traceback.TracebackException(*exc_info, limit=-1)
+        exc5 = traceback.TracebackException(*exc_info, limit=-1, capture_locals=True)
+        self.assertEqual(exc4, exc5)
+
+        # there are locals in the next-to-innermost frame
+        exc6 = traceback.TracebackException(*exc_info, limit=-2)
+        exc7 = traceback.TracebackException(*exc_info, limit=-2, capture_locals=True)
+        self.assertNotEqual(exc6, exc7)
+
     def test_unhashable(self):
         class UnhashableException(Exception):
             def __eq__(self, other):
@@ -1156,7 +1193,7 @@ class TestTracebackException(unittest.TestCase):
         f = test_frame(c, None, None)
         tb = test_tb(f, 6, None)
         exc = traceback.TracebackException(Exception, e, tb, lookup_lines=False)
-        self.assertEqual({}, linecache.cache)
+        self.assertEqual(linecache.cache, {})
         linecache.updatecache('/foo.py', globals())
         self.assertEqual(exc.stack[0].line, "import sys")