Firestore: client.collections() raising exception on list expansion

[crwilcox]

Python 3.7.2 (default, Mar  7 2019, 12:37:36)
[Clang 10.0.0 (clang-1000.10.44.4)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> from google.cloud import firestore
>>> client = firestore.Client()
>>> collections = client.collections()
>>> list(collections)

Traceback (most recent call last):
  File "/Users/crwilcox/scratch/google-cloud-firestore/venv/lib/python3.7/site-packages/google/api_core/grpc_helpers.py", line 57, in error_remapped_callable
    return callable_(*args, **kwargs)
  File "/Users/crwilcox/scratch/google-cloud-firestore/venv/lib/python3.7/site-packages/grpc/_channel.py", line 565, in __call__
    return _end_unary_response_blocking(state, call, False, None)
  File "/Users/crwilcox/scratch/google-cloud-firestore/venv/lib/python3.7/site-packages/grpc/_channel.py", line 467, in _end_unary_response_blocking
    raise _Rendezvous(state, None, None, deadline)
grpc._channel._Rendezvous: <_Rendezvous of RPC that terminated with:
	status = StatusCode.INVALID_ARGUMENT
	details = "Document parent name "projects/abstract-disk-227418/databases/(default)" lacks "/" at index 49."
	debug_error_string = "{"created":"@1563560373.944638000","description":"Error received from peer ipv6:[2607:f8b0:400a:804::200a]:443","file":"src/core/lib/surface/call.cc","file_line":1052,"grpc_message":"Document parent name "projects/abstract-disk-227418/databases/(default)" lacks "/" at index 49.","grpc_status":3}"
>

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/Users/crwilcox/scratch/google-cloud-firestore/venv/lib/python3.7/site-packages/google/api_core/page_iterator.py", line 204, in _items_iter
    for page in self._page_iter(increment=False):
  File "/Users/crwilcox/scratch/google-cloud-firestore/venv/lib/python3.7/site-packages/google/api_core/page_iterator.py", line 235, in _page_iter
    page = self._next_page()
  File "/Users/crwilcox/scratch/google-cloud-firestore/venv/lib/python3.7/site-packages/google/api_core/page_iterator.py", line 526, in _next_page
    response = self._method(self._request)
  File "/Users/crwilcox/scratch/google-cloud-firestore/venv/lib/python3.7/site-packages/google/api_core/gapic_v1/method.py", line 143, in __call__
    return wrapped_func(*args, **kwargs)
  File "/Users/crwilcox/scratch/google-cloud-firestore/venv/lib/python3.7/site-packages/google/api_core/retry.py", line 273, in retry_wrapped_func
    on_error=on_error,
  File "/Users/crwilcox/scratch/google-cloud-firestore/venv/lib/python3.7/site-packages/google/api_core/retry.py", line 182, in retry_target
    return target()
  File "/Users/crwilcox/scratch/google-cloud-firestore/venv/lib/python3.7/site-packages/google/api_core/timeout.py", line 214, in func_with_timeout
    return func(*args, **kwargs)
  File "/Users/crwilcox/scratch/google-cloud-firestore/venv/lib/python3.7/site-packages/google/api_core/grpc_helpers.py", line 59, in error_remapped_callable
    six.raise_from(exceptions.from_grpc_error(exc), exc)
  File "<string>", line 3, in raise_from
google.api_core.exceptions.InvalidArgument: 400 Document parent name "projects/abstract-disk-227418/databases/(default)" lacks "/" at index 49.

[tseaver]

Interesting. When Client.collections was added in #6553, we were on the v1beta1 API only: the method actually works for the firestore_v1beta1.Client class!

>>> from google.cloud.firestore_v1beta1 import Client
>>> client = Client()
>>> collections = list(client.collections())
>>> type(collections)
list

While investigating, I tried poking at the V1 client code to add a trailing / to the parent string passed to ListCollectionIds, which provoked a different exception:

Traceback (most recent call last):
  File ".../api_core/google/api_core/grpc_helpers.py", line 57, in error_remapped_callable
    return callable_(*args, **kwargs)
  File ".../.nox/system-3-7/lib/python3.7/site-packages/grpc/_channel.py", line 565, in __call__
    return _end_unary_response_blocking(state, call, False, None)
  File ".../.nox/system-3-7/lib/python3.7/site-packages/grpc/_channel.py", line 467, in _end_unary_response_blocking
    raise _Rendezvous(state, None, None, deadline)
grpc._channel._Rendezvous: <_Rendezvous of RPC that terminated with:
	status = StatusCode.INVALID_ARGUMENT
	details = "Document parent name "projects/<PROJECT-ID>/databases/(default)/" has invalid trailing "/"."
	debug_error_string = "{"created":"@1563563139.296441652","description":"Error received from peer ipv6:[2607:f8b0:4004:805::200a]:443","file":"src/core/lib/surface/call.cc","file_line":1052,"grpc_message":"Document parent name "projects/<PROJECT-ID>/databases/(default)/" has invalid trailing "/".","grpc_status":3}"
>

I then recalled some more of the undocumented behavior from other V1 changes, which require that the client pass /documents as the top-level path. I tried hacking that onto the parent passed to ListCollectionIds, and voilà! no exception.