Add cancellation interop tests for Python

Fixes #1591.

Also fixes a raised-exceptions-during-tests-causes-hanging problem.

src/python/interop/interop/_interop_test_case.py

@@ -53,3 +53,9 @@ class InteropTestCase(object):
 
   def testPingPong(self):
     methods.TestCase.PING_PONG.test_interoperability(self.stub, None)
+
+  def testCancelAfterBegin(self):
+    methods.TestCase.CANCEL_AFTER_BEGIN.test_interoperability(self.stub, None)
+
+  def testCancelAfterFirstResponse(self):
+    methods.TestCase.CANCEL_AFTER_FIRST_RESPONSE.test_interoperability(self.stub, None)

src/python/interop/interop/methods.py

@@ -219,6 +219,17 @@ def _server_streaming(stub):
         raise ValueError(
             'response body of invalid size %d!' % len(response.payload.body))
 
+def _cancel_after_begin(stub):
+  with stub:
+    sizes = (27182, 8, 1828, 45904)
+    payloads = [messages_pb2.Payload(body=b'\x00' * size) for size in sizes]
+    requests = [messages_pb2.StreamingInputCallRequest(payload=payload)
+                for payload in payloads]
+    responses = stub.StreamingInputCall.async(requests, _TIMEOUT)
+    responses.cancel()
+    if not responses.cancelled():
+      raise ValueError('expected call to be cancelled')
+
 
 class _Pipe(object):
 
@@ -249,13 +260,18 @@ class _Pipe(object):
       self._open = False
       self._condition.notify()
 
+  def __enter__(self):
+    return self
+
+  def __exit__(self, type, value, traceback):
+    self.close()
+
 
 def _ping_pong(stub):
   request_response_sizes = (31415, 9, 2653, 58979)
   request_payload_sizes = (27182, 8, 1828, 45904)
 
-  with stub:
-    pipe = _Pipe()
+  with stub, _Pipe() as pipe:
     response_iterator = stub.FullDuplexCall(pipe, _TIMEOUT)
     print 'Starting ping-pong with response iterator %s' % response_iterator
     for response_size, payload_size in zip(
@@ -273,7 +289,33 @@ def _ping_pong(stub):
       if len(response.payload.body) != response_size:
         raise ValueError(
             'response body of invalid size %d!' % len(response.payload.body))
-    pipe.close()
+
+
+def _cancel_after_first_response(stub):
+  request_response_sizes = (31415, 9, 2653, 58979)
+  request_payload_sizes = (27182, 8, 1828, 45904)
+  with stub, _Pipe() as pipe:
+    response_iterator = stub.FullDuplexCall(pipe, _TIMEOUT)
+
+    response_size = request_response_sizes[0]
+    payload_size = request_payload_sizes[0]
+    request = messages_pb2.StreamingOutputCallRequest(
+        response_type=messages_pb2.COMPRESSABLE,
+        response_parameters=(messages_pb2.ResponseParameters(
+            size=response_size),),
+        payload=messages_pb2.Payload(body=b'\x00' * payload_size))
+    pipe.add(request)
+    response = next(response_iterator)
+    # We test the contents of `response` in the Ping Pong test - don't check
+    # them here.
+    response_iterator.cancel()
+
+    try:
+      next(response_iterator)
+    except Exception:
+      pass
+    else:
+      raise ValueError('expected call to be cancelled')
 
 
 def _compute_engine_creds(stub, args):
@@ -305,6 +347,8 @@ class TestCase(enum.Enum):
   SERVER_STREAMING = 'server_streaming'
   CLIENT_STREAMING = 'client_streaming'
   PING_PONG = 'ping_pong'
+  CANCEL_AFTER_BEGIN = 'cancel_after_begin'
+  CANCEL_AFTER_FIRST_RESPONSE = 'cancel_after_first_response'
   COMPUTE_ENGINE_CREDS = 'compute_engine_creds'
   SERVICE_ACCOUNT_CREDS = 'service_account_creds'
 
@@ -319,6 +363,10 @@ class TestCase(enum.Enum):
       _client_streaming(stub)
     elif self is TestCase.PING_PONG:
       _ping_pong(stub)
+    elif self is TestCase.CANCEL_AFTER_BEGIN:
+      _cancel_after_begin(stub)
+    elif self is TestCase.CANCEL_AFTER_FIRST_RESPONSE:
+      _cancel_after_first_response(stub)
     elif self is TestCase.COMPUTE_ENGINE_CREDS:
       _compute_engine_creds(stub, args)
     elif self is TestCase.SERVICE_ACCOUNT_CREDS: