fix: PubSub incompatibility with api-core 1.17.0+ (googleapis#103)

* fix: disable pre-fetching first streaming pull item

* Remove api-core version cap, but ban 1.17.0 release

* Regenerate gapic layer with synth

* Revert "Regenerate gapic layer with synth"

This reverts commit 1d24853.

* Retain only the relevant fix in generated code

* Exclude multiple incompatible api-core versions

* Fix syntax error in synth.py

* Ban all bugfix versions of problematic api-core minor versions

google/cloud/pubsub_v1/gapic/subscriber_client.py

@@ -1175,6 +1175,11 @@ def streaming_pull(
                 client_info=self._client_info,
             )
 
+            # Wrappers in api-core should not automatically pre-fetch the first
+            # stream result, as this breaks the stream when re-opening it.
+            # https://github.com/googleapis/python-pubsub/issues/93#issuecomment-630762257
+            self.transport.streaming_pull._prefetch_first_result_ = False
+
         return self._inner_api_calls["streaming_pull"](
             requests, retry=retry, timeout=timeout, metadata=metadata
         )

setup.py

@@ -29,10 +29,10 @@
 # 'Development Status :: 5 - Production/Stable'
 release_status = "Development Status :: 5 - Production/Stable"
 dependencies = [
-    # google-api-core[grpc] 1.17.0 causes problems, thus restricting its
-    # version until the issue gets fixed.
+    # google-api-core[grpc] 1.17.0 up to 1.19.1 causes problems with stream
+    # recovery, thus those versions should not be used.
     # https://github.com/googleapis/python-pubsub/issues/74
-    "google-api-core[grpc] >= 1.14.0, < 1.17.0",
+    "google-api-core[grpc] >= 1.14.0, != 1.17.*, != 1.18.*, != 1.19.*",
     "grpc-google-iam-v1 >= 0.12.3, < 0.13dev",
     'enum34; python_version < "3.4"',
 ]

synth.py

@@ -185,6 +185,20 @@ def _merge_dict(d1, d2):
     "from google.iam.v1 import iam_policy_pb2_grpc as iam_policy_pb2",
 )
 
+# Monkey patch the streaming_pull() GAPIC method to disable pre-fetching stream
+# results.
+s.replace(
+    "google/cloud/pubsub_v1/gapic/subscriber_client.py",
+    r"return self\._inner_api_calls\['streaming_pull'\]\(.*",
+    """
+            # Wrappers in api-core should not automatically pre-fetch the first
+            # stream result, as this breaks the stream when re-opening it.
+            # https://github.com/googleapis/python-pubsub/issues/93#issuecomment-630762257
+            self.transport.streaming_pull._prefetch_first_result_ = False
+
+        \g<0>"""
+)
+
 # Add missing blank line before Attributes: in generated docstrings
 # https://github.com/googleapis/protoc-docs-plugin/pull/31
 s.replace(

tests/unit/pubsub_v1/subscriber/test_subscriber_client.py

@@ -154,3 +154,15 @@ def test_closes_channel_as_context_manager():
         pass
 
     mock_transport.channel.close.assert_called()
+
+
+def test_streaming_pull_gapic_monkeypatch():
+    transport = mock.NonCallableMock(spec=["streaming_pull"])
+    transport.streaming_pull = mock.Mock(spec=[])
+    client = subscriber.Client(transport=transport)
+
+    client.streaming_pull(requests=iter([]))
+
+    assert client.api.transport is transport
+    assert hasattr(transport.streaming_pull, "_prefetch_first_result_")
+    assert not transport.streaming_pull._prefetch_first_result_