bpo-29587: Update gen.throw() to chain exceptions (#19823)
Before this commit, if an exception was active inside a generator
when calling gen.throw(), that exception was lost (i.e. there was
no implicit exception chaining). This commit fixes that by
setting exc.__context__ when calling gen.throw(exc).
diff --git a/Lib/test/test_generators.py b/Lib/test/test_generators.py
index 3e42bc6..4d96f44 100644
--- a/Lib/test/test_generators.py
+++ b/Lib/test/test_generators.py
@@ -316,6 +316,23 @@
self.assertEqual(cm.exception.value.value, 2)
+class GeneratorThrowTest(unittest.TestCase):
+
+ def test_exception_context_set(self):
+ def f():
+ try:
+ raise KeyError('a')
+ except Exception:
+ yield
+
+ gen = f()
+ gen.send(None)
+ with self.assertRaises(ValueError) as cm:
+ gen.throw(ValueError)
+ context = cm.exception.__context__
+ self.assertEqual((type(context), context.args), (KeyError, ('a',)))
+
+
class YieldFromTests(unittest.TestCase):
def test_generator_gi_yieldfrom(self):
def a():
diff --git a/Misc/NEWS.d/next/Core and Builtins/2020-04-30-00-50-25.bpo-29587.oEwSq.rst b/Misc/NEWS.d/next/Core and Builtins/2020-04-30-00-50-25.bpo-29587.oEwSq.rst
new file mode 100644
index 0000000..f44aa36
--- /dev/null
+++ b/Misc/NEWS.d/next/Core and Builtins/2020-04-30-00-50-25.bpo-29587.oEwSq.rst
@@ -0,0 +1 @@
+Enable implicit exception chaining when calling :meth:`generator.throw`.
diff --git a/Objects/genobject.c b/Objects/genobject.c
index 6e36690..41a63ae 100644
--- a/Objects/genobject.c
+++ b/Objects/genobject.c
@@ -512,6 +512,15 @@
}
PyErr_Restore(typ, val, tb);
+ /* XXX Should we also handle the case where exc_type is true and
+ exc_value is false? */
+ if (gen->gi_exc_state.exc_type && gen->gi_exc_state.exc_value) {
+ Py_INCREF(gen->gi_exc_state.exc_type);
+ Py_INCREF(gen->gi_exc_state.exc_value);
+ Py_XINCREF(gen->gi_exc_state.exc_traceback);
+ _PyErr_ChainExceptions(gen->gi_exc_state.exc_type,
+ gen->gi_exc_state.exc_value, gen->gi_exc_state.exc_traceback);
+ }
return gen_send_ex(gen, Py_None, 1, 0);
failed_throw: