fix: do not error on LROs with no response or error

google/api_core/operation.py

@@ -140,11 +140,11 @@ def _set_result_from_operation(self):
  )
  self.set_exception(exception)
  else:
- exception = exceptions.GoogleAPICallError(
-  "Unexpected state: Long-running operation had neither "
-  "response nor error set."
- )
- self.set_exception(exception)
+ # Some APIs set `done: true`, with an empty response.
+ # Set the result to an empty message of the expected
+ # result type.
+ # https://google.aip.dev/151
+ self.set_result(self._result_type())
 
  def _refresh_and_update(self, retry=polling.DEFAULT_RETRY):
  """Refresh the operation and update the result if needed.

google/api_core/operation_async.py

@@ -136,11 +136,11 @@ def _set_result_from_operation(self):
  )
  self.set_exception(exception)
  else:
- exception = exceptions.GoogleAPICallError(
-  "Unexpected state: Long-running operation had neither "
-  "response nor error set."
- )
- self.set_exception(exception)
+ # Some APIs set `done: true`, with an empty response.
+ # Set the result to an empty message of the expected
+ # result type.
+ # https://google.aip.dev/151
+ self.set_result(self._result_type())
 
  async def _refresh_and_update(self, retry=async_future.DEFAULT_RETRY):
  """Refresh the operation and update the result if needed.

tests/asyncio/test_operation_async.py

@@ -153,17 +153,17 @@ async def test_exception():
 
 @mock.patch("asyncio.sleep", autospec=True)
 @pytest.mark.asyncio
-async def test_unexpected_result(unused_sleep):
+async def test_done_with_no_error_or_response(unused_sleep):
  responses = [
  make_operation_proto(),
  # Second operation response is done, but has not error or response.
  make_operation_proto(done=True),
  ]
  future, _, _ = make_operation_future(responses)
 
- exception = await future.exception()
+ result = await future.result()
 
- assert "Unexpected state" in "{!r}".format(exception)
+ assert isinstance(result, struct_pb2.Struct)
 
 
 def test_from_gapic():

tests/unit/test_operation.py

@@ -163,17 +163,15 @@ def test_exception_with_error_code():
  assert isinstance(exception, exceptions.NotFound)
 
 
-def test_unexpected_result():
+def test_done_with_no_error_or_response():
  responses = [
  make_operation_proto(),
  # Second operation response is done, but has not error or response.
  make_operation_proto(done=True),
  ]
  future, _, _ = make_operation_future(responses)
 
- exception = future.exception()
-
- assert "Unexpected state" in "{!r}".format(exception)
+ assert isinstance(future.result(), struct_pb2.Struct)
 
 
 def test__refresh_http():