Fix a problem with @contextmanager not detecting a broken generator

that yields after a throw().  Make @contextmanager not reraise
exceptions, but return a false value in that case instead.  Add test
cases for both behaviors.

1 files changed, 22 insertions, 0 deletions

diff --git a/Lib/test/test_contextlib.py b/Lib/test/test_contextlib.py
index f8db88c..7d7f8d2 100644
--- a/Lib/test/test_contextlib.py
+++ b/Lib/test/test_contextlib.py
@@ -45,6 +45,28 @@ class ContextManagerTestCase(unittest.TestCase):
             self.fail("Expected ZeroDivisionError")
         self.assertEqual(state, [1, 42, 999])
 
+    def test_contextmanager_no_reraise(self):
+        @contextmanager
+        def whee():
+            yield
+        ctx = whee().__context__()
+        ctx.__enter__()
+        # Calling __exit__ should not result in an exception
+        self.failIf(ctx.__exit__(TypeError, TypeError("foo"), None))
+
+    def test_contextmanager_trap_yield_after_throw(self):
+        @contextmanager
+        def whoo():
+            try:
+                yield
+            except:
+                yield
+        ctx = whoo().__context__()
+        ctx.__enter__()
+        self.assertRaises(
+            RuntimeError, ctx.__exit__, TypeError, TypeError("foo"), None
+        )
+
     def test_contextmanager_except(self):
         state = []
         @contextmanager