Protocol.for_id: add remote kwarg

protocol.py

@@ -226,19 +226,18 @@ class Protocol:
 
     @cached(LRUCache(20000), lock=Lock())
     @staticmethod
-    def for_id(id):
+    def for_id(id, remote=True):
         """Returns the protocol for a given id.
 
-        May incur expensive side effects like fetching the id itself over the
-        network or other discovery.
-
         Args:
           id (str)
+          remote (bool): whether to perform expensive side effects like fetching
+            the id itself over the network, or other discovery.
 
         Returns:
-          Protocol subclass: matching protocol, or None if no known protocol
-          owns this id
-       """
+          Protocol subclass: matching protocol, or None if no single known
+          protocol definitively owns this id
+        """
         logger.info(f'Determining protocol for id {id}')
         if not id:
             return None
@@ -273,7 +272,10 @@ class Protocol:
             logger.info(f'  {obj.key} owned by source_protocol {obj.source_protocol}')
             return PROTOCOLS[obj.source_protocol]
 
-        # step 4: fetch over the network
+        # step 4: fetch over the network, if necessary
+        if not remote:
+            return None
+
         for protocol in candidates:
             logger.info(f'Trying {protocol.LABEL}')
             try:

tests/test_protocol.py

@@ -93,7 +93,8 @@ class ProtocolTest(TestCase):
                 ('https://ap.brid.gy/foo/bar', ActivityPub),
                 ('https://web.brid.gy/foo/bar', Web),
         ]:
-            self.assertEqual(expected, Protocol.for_id(id))
+            self.assertEqual(expected, Protocol.for_id(id, remote=False))
+            self.assertEqual(expected, Protocol.for_id(id, remote=True))
 
     def test_for_id_true_overrides_none(self):
         class Greedy(Protocol, User):
@@ -137,6 +138,11 @@ class ProtocolTest(TestCase):
         self.assertIsNone(Protocol.for_id('http://web.site/'))
         self.assertIn(self.req('http://web.site/'), mock_get.mock_calls)
 
+    @patch('requests.get')
+    def test_for_id_web_remote_false(self, mock_get):
+        self.assertIsNone(Protocol.for_id('http://web.site/', remote=False))
+        mock_get.assert_not_called()
+
     def test_for_handle_deterministic(self):
         for handle, expected in [
             (None, (None, None)),