add a tonne of docstring; make upload_room_keys properly assert version

synapse/storage/e2e_room_keys.py

@@ -67,6 +67,7 @@ class EndToEndRoomKeyStore(SQLBaseStore):
             version(str): the version ID of the backup we're updating
             room_id(str): the ID of the room whose keys we're setting
             session_id(str): the session whose room_key we're setting
+            room_key(dict): the room_key being set
         Raises:
             StoreError if stuff goes wrong, probably
         """
@@ -182,19 +183,28 @@ class EndToEndRoomKeyStore(SQLBaseStore):
             desc="delete_e2e_room_keys",
         )
 
-    @defer.inlineCallbacks
-    def get_e2e_room_keys_version_info(self, user_id, version):
-        """Get info etadata about a given version of our room_keys backup
+    def get_e2e_room_keys_version_info(self, user_id, version=None):
+        """Get info metadata about a version of our room_keys backup.
 
         Args:
             user_id(str): the user whose backup we're querying
-            version(str): the version ID of the backup we're querying about
-
+            version(str): Optional. the version ID of the backup we're querying about
+                If missing, we return the information about the current version.
+        Raises:
+            StoreError: with code 404 if there are no e2e_room_keys_versions present
         Returns:
             A deferred dict giving the info metadata for this backup version
         """
 
-        row = yield self._simple_select_one(
+        def _get_e2e_room_keys_version_info_txn(txn):
+            if version is None:
+                txn.execute(
+                    "SELECT MAX(version) FROM e2e_room_keys_versions WHERE user_id=?",
+                    (user_id,)
+                )
+                version = txn.fetchone()[0]
+
+            return self._simple_select_one_txn(
                 table="e2e_room_keys_versions",
                 keyvalues={
                     "user_id": user_id,
@@ -206,10 +216,12 @@ class EndToEndRoomKeyStore(SQLBaseStore):
                     "algorithm",
                     "auth_data",
                 ),
-            desc="get_e2e_room_keys_version_info",
             )
 
-        defer.returnValue(row)
+        return self.runInteraction(
+            desc="get_e2e_room_keys_version_info",
+            _get_e2e_room_keys_version_info_txn
+        )
 
     def create_e2e_room_keys_version(self, user_id, info):
         """Atomically creates a new version of this user's e2e_room_keys store
@@ -224,7 +236,6 @@ class EndToEndRoomKeyStore(SQLBaseStore):
         """
 
         def _create_e2e_room_keys_version_txn(txn):
-
             txn.execute(
                 "SELECT MAX(version) FROM e2e_room_keys_versions WHERE user_id=?",
                 (user_id,)