Issue #23353: Fix the exception handling of generators in PyEval_EvalFrameEx().

At entry, save or swap the exception state even if PyEval_EvalFrameEx() is
called with throwflag=0. At exit, the exception state is now always restored or
swapped, not only if why is WHY_YIELD or WHY_RETURN. Patch co-written with
Antoine Pitrou.

1 files changed, 109 insertions, 0 deletions

diff --git a/Lib/test/test_generators.py b/Lib/test/test_generators.py
index 91afe47..7825a77 100644
--- a/Lib/test/test_generators.py
+++ b/Lib/test/test_generators.py
@@ -50,6 +50,115 @@ class FinalizationTest(unittest.TestCase):
         self.assertEqual(gc.garbage, old_garbage)
 
 
+class ExceptionTest(unittest.TestCase):
+    # Tests for the issue #23353: check that the currently handled exception
+    # is correctly saved/restored in PyEval_EvalFrameEx().
+
+    def test_except_throw(self):
+        def store_raise_exc_generator():
+            try:
+                self.assertEqual(sys.exc_info()[0], None)
+                yield
+            except Exception as exc:
+                # exception raised by gen.throw(exc)
+                self.assertEqual(sys.exc_info()[0], ValueError)
+                self.assertIsNone(exc.__context__)
+                yield
+
+                # ensure that the exception is not lost
+                self.assertEqual(sys.exc_info()[0], ValueError)
+                yield
+
+                # we should be able to raise back the ValueError
+                raise
+
+        make = store_raise_exc_generator()
+        next(make)
+
+        try:
+            raise ValueError()
+        except Exception as exc:
+            try:
+                make.throw(exc)
+            except Exception:
+                pass
+
+        next(make)
+        with self.assertRaises(ValueError) as cm:
+            next(make)
+        self.assertIsNone(cm.exception.__context__)
+
+        self.assertEqual(sys.exc_info(), (None, None, None))
+
+    def test_except_next(self):
+        def gen():
+            self.assertEqual(sys.exc_info()[0], ValueError)
+            yield "done"
+
+        g = gen()
+        try:
+            raise ValueError
+        except Exception:
+            self.assertEqual(next(g), "done")
+        self.assertEqual(sys.exc_info(), (None, None, None))
+
+    def test_except_gen_except(self):
+        def gen():
+            try:
+                self.assertEqual(sys.exc_info()[0], None)
+                yield
+                # we are called from "except ValueError:", TypeError must
+                # inherit ValueError in its context
+                raise TypeError()
+            except TypeError as exc:
+                self.assertEqual(sys.exc_info()[0], TypeError)
+                self.assertEqual(type(exc.__context__), ValueError)
+            # here we are still called from the "except ValueError:"
+            self.assertEqual(sys.exc_info()[0], ValueError)
+            yield
+            self.assertIsNone(sys.exc_info()[0])
+            yield "done"
+
+        g = gen()
+        next(g)
+        try:
+            raise ValueError
+        except Exception:
+            next(g)
+
+        self.assertEqual(next(g), "done")
+        self.assertEqual(sys.exc_info(), (None, None, None))
+
+    def test_except_throw_exception_context(self):
+        def gen():
+            try:
+                try:
+                    self.assertEqual(sys.exc_info()[0], None)
+                    yield
+                except ValueError:
+                    # we are called from "except ValueError:"
+                    self.assertEqual(sys.exc_info()[0], ValueError)
+                    raise TypeError()
+            except Exception as exc:
+                self.assertEqual(sys.exc_info()[0], TypeError)
+                self.assertEqual(type(exc.__context__), ValueError)
+            # we are still called from "except ValueError:"
+            self.assertEqual(sys.exc_info()[0], ValueError)
+            yield
+            self.assertIsNone(sys.exc_info()[0])
+            yield "done"
+
+        g = gen()
+        next(g)
+        try:
+            raise ValueError
+        except Exception as exc:
+            g.throw(exc)
+
+        self.assertEqual(next(g), "done")
+        self.assertEqual(sys.exc_info(), (None, None, None))
+
+
 tutorial_tests = """
 Let's try a simple generator: