prevent generator methods from returning NULL without setting an exception:...

prevent generator methods from returning NULL without setting an exception: method call protocol differs from __next__() protocol

Cython/Utility/Generator.c

@@ -260,6 +260,15 @@ PyObject *__Pyx_Generator_SendEx(__pyx_GeneratorObject *self, PyObject *value) {
     return retval;
 }
 
+static CYTHON_INLINE
+PyObject *__Pyx_Generator_MethodReturn(PyObject *retval) {
+    if (unlikely(!retval && !PyErr_Occurred())) {
+        // method call must not terminate with NULL without setting an exception
+        PyErr_SetNone(PyExc_StopIteration);
+    }
+    return retval;
+}
+
 static CYTHON_INLINE
 PyObject *__Pyx_Generator_FinishDelegation(__pyx_GeneratorObject *gen) {
     PyObject *ret;
@@ -295,6 +304,7 @@ static PyObject *__Pyx_Generator_Next(PyObject *self) {
 }
 
 static PyObject *__Pyx_Generator_Send(PyObject *self, PyObject *value) {
+    PyObject *retval;
     __pyx_GeneratorObject *gen = (__pyx_GeneratorObject*) self;
     PyObject *yf = gen->yieldfrom;
     if (unlikely(__Pyx_Generator_CheckRunning(gen)))
@@ -317,9 +327,11 @@ static PyObject *__Pyx_Generator_Send(PyObject *self, PyObject *value) {
         if (likely(ret)) {
             return ret;
         }
-        return __Pyx_Generator_FinishDelegation(gen);
+        retval = __Pyx_Generator_FinishDelegation(gen);
+    } else {
+        retval = __Pyx_Generator_SendEx(gen, value);
     }
-    return __Pyx_Generator_SendEx(gen, value);
+    return __Pyx_Generator_MethodReturn(retval);
 }
 
 //   This helper function is used by gen_close and gen_throw to
@@ -413,7 +425,7 @@ static PyObject *__Pyx_Generator_Throw(PyObject *self, PyObject *args) {
             Py_DECREF(yf);
             __Pyx_Generator_Undelegate(gen);
             if (err < 0)
-                return __Pyx_Generator_SendEx(gen, NULL);
+                return __Pyx_Generator_MethodReturn(__Pyx_Generator_SendEx(gen, NULL));
             goto throw_here;
         }
         gen->is_running = 1;
@@ -440,11 +452,11 @@ static PyObject *__Pyx_Generator_Throw(PyObject *self, PyObject *args) {
         if (!ret) {
             ret = __Pyx_Generator_FinishDelegation(gen);
         }
-        return ret;
+        return __Pyx_Generator_MethodReturn(ret);
     }
 throw_here:
     __Pyx_Raise(typ, val, tb, NULL);
-    return __Pyx_Generator_SendEx(gen, NULL);
+    return __Pyx_Generator_MethodReturn(__Pyx_Generator_SendEx(gen, NULL));
 }
 
 static int __Pyx_Generator_traverse(PyObject *self, visitproc visit, void *arg) {

tests/run/generators.pyx

@@ -309,6 +309,76 @@ def test_return(a):
     a['i_was_here'] = True
     return
 
+
+def test_return_in_finally(a):
+    """
+    >>> d = dict()
+    >>> obj = test_return_in_finally(d)
+    >>> next(obj)
+    1
+    >>> next(obj)
+    Traceback (most recent call last):
+    StopIteration
+    >>> d['i_was_here']
+    True
+
+    >>> d = dict()
+    >>> obj = test_return_in_finally(d)
+    >>> next(obj)
+    1
+    >>> obj.send(2)
+    Traceback (most recent call last):
+    StopIteration
+    >>> d['i_was_here']
+    True
+
+    >>> obj = test_return_in_finally(None)
+    >>> next(obj)
+    1
+    >>> next(obj)
+    Traceback (most recent call last):
+    StopIteration
+
+    >>> obj = test_return_in_finally(None)
+    >>> next(obj)
+    1
+    >>> obj.send(2)
+    Traceback (most recent call last):
+    StopIteration
+    """
+    yield 1
+    try:
+        a['i_was_here'] = True
+    finally:
+        return
+
+
+def test_return_none_in_finally(a):
+    """
+    >>> d = dict()
+    >>> obj = test_return_none_in_finally(d)
+    >>> next(obj)
+    1
+    >>> next(obj)
+    Traceback (most recent call last):
+    StopIteration
+    >>> d['i_was_here']
+    True
+
+    >>> obj = test_return_none_in_finally(None)
+    >>> next(obj)
+    1
+    >>> next(obj)
+    Traceback (most recent call last):
+    StopIteration
+    """
+    yield 1
+    try:
+        a['i_was_here'] = True
+    finally:
+        return None
+
+
 def test_copied_yield(foo):
     """
     >>> class Manager(object):