feat: Key.to_legacy_urlsafe() (#348)

* #264 Create method `legacy_urlsafe` to include location prefix in a urlsafe key

* Update docstring, rename to match Datastore for consistency.

* Fix test.

* Make suggested changes from code review.

Co-authored-by: Thomas Cross <tom.bz2@gmail.com>

Author: Chris Rossi

packages/google-cloud-ndb/google/cloud/ndb/key.py

@@ -728,7 +728,7 @@ def serialized(self):
         return reference.SerializeToString()
 
     def urlsafe(self):
-        """A ``Reference`` protobuf encoded as urlsafe base 64.
+        """A ``Reference`` protobuf serialized and encoded as urlsafe base 64.
 
         .. doctest:: key-urlsafe
 
@@ -739,6 +739,33 @@ def urlsafe(self):
         raw_bytes = self.serialized()
         return base64.urlsafe_b64encode(raw_bytes).strip(b"=")
 
+    def to_legacy_urlsafe(self, location_prefix):
+        """
+        A urlsafe serialized ``Reference`` protobuf with an App Engine prefix.
+
+        This will produce a urlsafe string which includes an App Engine
+        location prefix ("partition"), compatible with the Google Datastore
+        admin console.
+
+        Arguments:
+            location_prefix (str): A location prefix ("partition") to be
+                prepended to the key's `project` when serializing the key. A
+                typical value is "s~", but "e~" or other partitions are
+                possible depending on the project's region and other factors.
+
+        .. doctest:: key-legacy-urlsafe
+
+            >>> key = ndb.Key("Kind", 1337, project="example")
+            >>> key.to_legacy_urlsafe("s~")
+            b'aglzfmV4YW1wbGVyCwsSBEtpbmQYuQoM'
+        """
+        return google.cloud.datastore.Key(
+            self._key.kind,
+            self._key.id,
+            namespace=self._key.namespace,
+            project=self._key.project,
+        ).to_legacy_urlsafe(location_prefix=location_prefix)
+
     @_options.ReadOptions.options
     @utils.positional(1)
     def get(

packages/google-cloud-ndb/tests/unit/test_key.py

@@ -567,6 +567,15 @@ def test_urlsafe():
         key = key_module.Key("d", None, app="f")
         assert key.urlsafe() == b"agFmcgULEgFkDA"
 
+    @staticmethod
+    @pytest.mark.usefixtures("in_context")
+    def test_to_legacy_urlsafe():
+        key = key_module.Key("d", 123, app="f")
+        assert (
+            key.to_legacy_urlsafe(location_prefix="s~")
+            == b"agNzfmZyBwsSAWQYeww"
+        )
+
     @staticmethod
     @pytest.mark.usefixtures("in_context")
     @mock.patch("google.cloud.ndb._datastore_api")