Datastore batches distinguish between "" and None on delete_multi and throw

[rwhogg]

Environment details

• OS type and version: Linux
• Python version: 3.8.15
• pip version: 23.2
• google-cloud-datastore version:

Name: google-cloud-datastore
Version: 2.16.1
Summary: Google Cloud Datastore API client library
Home-page: https://github.com/googleapis/python-datastore
Author: Google LLC
Author-email: googleapis-packages@google.com
License: Apache 2.0
Location: /home/rwhogg/.pyenv/versions/3.8.15/lib/python3.8/site-packages
Requires: google-api-core, google-cloud-core, proto-plus, protobuf
Required-by: google-cloud-ndb

Steps to reproduce

1. Get some keys with database == ""
2. Get a datastore client with database of None
3. Call delete_multi on those keys

Code example

# batchbug.py
from google.cloud.datastore.client import Client

client = Client(project="myproject")

# Get some keys
query = client.query(kind="somekind")
query.keys_only()
for page in query.fetch().pages:
    keys = [entity.key for entity in page]

# Change the keys to have database == "".
# This isn't the normal way you would do this, it's just for reproducing the bug
keys = map(lambda k: k.__class__(
    *k.flat_path,
    project=k.project,
    database="",
    namespace=k.namespace
), keys)

# batch delete - throws error
client.delete_multi(keys)

Stack trace

Traceback (most recent call last):
  File "batchbug.py", line 18, in <module>
    client.delete_multi(keys)
  File "/home/rwhogg/.pyenv/versions/3.8.15/lib/python3.8/site-packages/google/cloud/datastore/client.py", line 721, in delete_multi
    current.delete(key)
  File "/home/rwhogg/.pyenv/versions/3.8.15/lib/python3.8/site-packages/google/cloud/datastore/batch.py", line 261, in delete
    raise ValueError("Key must be from same database as batch")
ValueError: Key must be from same database as batch