fix: set creds only if transport not provided #1348
Merged
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GAPICs are designed to allow users to only configure one of transport or credentials. If a transport is configured explicitly, then it must be instantiated with credentials.
gapic-generator: See: https://github.com/googleapis/gapic-generator-python/blob/main/gapic/templates/%25namespace/%25name_%25version/%25sub/services/%25service/client.py.j2#L563.
pubsub: https://github.com/googleapis/python-pubsub/blob/main/google/pubsub_v1/services/publisher/client.py#L678
in google.cloud.pubsub_v1, if the environment variable
PUBSUB_EMULATOR_HOSTis set, the credentials are automatically set toAnonymousCredentialsin the client layer.This means that if
PUBSUB_EMULATOR_HOSTis set, then credentials are automatically configured under the hood for test cases.This behaviour results in an issue if a test sets
PUBSUB_EMULATOR_HOSTexplicitly and provides a transport to a client, resulting in the following error to be raised https://github.com/googleapis/python-pubsub/blob/main/google/pubsub_v1/services/publisher/client.py#L678.Given that we want to update the following test to explicitly configure a transport to the client (with an intercept channel), we want to make sure that credentials are provided to the transport instance and not on the client instance directly.