key.get() entity with compressed repeated LocalStructuredProperty(s) raise exception

[chmoder]

When retrieving entities with compressed repeated local structured properties an exception is thrown indicating that the repeated property a list not a decompress-able byte string.

https://github.com/googleapis/python-ndb/blob/release-v0.2.0/google/cloud/ndb/model.py#L2513

Please let me know how I can help!

Environment details

NOTE: this data was on original NDB datastore and we are using this library to fetch said data.

1. google-cloud-ndb
2. OS x
3. python 3.7.3
4. google-cloud-ndb 0.2.0

Steps to reproduce

1. find a key in an NDB datastore
2. key.get()

Code example

• assuming these are the classes*

class Dog(ndb.Model):
    name = ndb.StringProperty()


class House(ndb.Model):
    dogs = ndb.LocalStructuredProperty(Dog, repeated=True, compressed=True)


house = House()
house.dogs = [Dog(name='Mika'), Dog(name='Mocha')]
key = house.put()
entity = key.get()

Stack trace

Traceback (most recent call last):
  File "/usr/local/Cellar/python/3.7.3/Frameworks/Python.framework/Versions/3.7/lib/python3.7/contextlib.py", line 130, in __exit__
    self.gen.throw(type, value, traceback)
  File "/Users/tcross/development/virtual-environments/csgapi/lib/python3.7/site-packages/google/cloud/ndb/client.py", line 177, in context
    yield context
  File "/Users/tcross/development/csgapi/main.py", line 24, in <module>
    key = house.put()
  File "/Users/tcross/development/virtual-environments/csgapi/lib/python3.7/site-packages/google/cloud/ndb/_options.py", line 89, in wrapper
    return wrapped(*pass_args, **kwargs)
  File "/Users/tcross/development/virtual-environments/csgapi/lib/python3.7/site-packages/google/cloud/ndb/utils.py", line 78, in wrapper
    return wrapped(*args, **new_kwargs)
  File "/Users/tcross/development/virtual-environments/csgapi/lib/python3.7/site-packages/google/cloud/ndb/utils.py", line 109, in positional_wrapper
    return wrapped(*args, **kwds)
  File "/Users/tcross/development/virtual-environments/csgapi/lib/python3.7/site-packages/google/cloud/ndb/model.py", line 4921, in _put
    return self._put_async(_options=kwargs["_options"]).result()
  File "/Users/tcross/development/virtual-environments/csgapi/lib/python3.7/site-packages/google/cloud/ndb/tasklets.py", line 190, in result
    self.check_success()
  File "/Users/tcross/development/virtual-environments/csgapi/lib/python3.7/site-packages/google/cloud/ndb/tasklets.py", line 137, in check_success
    raise self._exception
  File "/Users/tcross/development/virtual-environments/csgapi/lib/python3.7/site-packages/google/cloud/ndb/tasklets.py", line 312, in _advance_tasklet
    yielded = self.generator.send(send_value)
  File "/Users/tcross/development/virtual-environments/csgapi/lib/python3.7/site-packages/google/cloud/ndb/model.py", line 4981, in put
    ds_entity = _entity_to_ds_entity(self)
  File "/Users/tcross/development/virtual-environments/csgapi/lib/python3.7/site-packages/google/cloud/ndb/model.py", line 722, in _entity_to_ds_entity
    names = prop._to_datastore(entity, data)
  File "/Users/tcross/development/virtual-environments/csgapi/lib/python3.7/site-packages/google/cloud/ndb/model.py", line 2495, in _to_datastore
    if value and not value.startswith(_ZLIB_COMPRESSION_MARKER):
AttributeError: 'list' object has no attribute 'startswith'

[cguardia]

@chmoder Thanks for the reports. We have a few issues with LocalStructuredPropety, so we'll take a look at the whole implementation.

[chmoder]

@cguardia, I went through and retested my code example. I think the way the entities were showing up empty was when I was modifying the library to get past this exception. So I updated this issue to start at the beginning where the exception was happening.