dms.receive: detect when the protocol doesn't support the requested u…

…ser's handle

fixes #1318

dms.py

@@ -7,6 +7,7 @@
 from oauth_dropins.webutil import util
 
 from common import create_task, memcache, memcache_key
+import ids
 import models
 import protocol
 
@@ -117,24 +118,31 @@ def receive(*, from_user, obj):
         content = content.removeprefix('@')
 
     if to_proto.owns_handle(content) is not False:
-        to_id = to_proto.handle_to_id(content)
-        if not to_id:
-            return reply(f"Couldn't find {to_proto.PHRASE} user {handle}")
+        handle = content
+        from_proto = from_user.__class__
 
         def reply(text, type=None):
             maybe_send(from_proto=to_proto, to_user=from_user, text=text, type=type)
             return 'OK', 200
 
+        try:
+            ids.translate_handle(handle=handle, from_=to_proto, to=from_user,
+                                 enhanced=False)
+        except ValueError as e:
+            logger.warning(e)
+            return reply(f"Sorry, Bridgy Fed doesn't yet support bridging handle {handle} from {to_proto.PHRASE} to {from_proto.PHRASE}.")
+
+        to_id = to_proto.handle_to_id(handle)
+        if not to_id:
+            return reply(f"Couldn't find {to_proto.PHRASE} user {handle}")
+
         if not from_user.is_enabled(to_proto):
             return reply(f'Please bridge your account to {to_proto.PHRASE} by following this account before requesting another user.')
 
-        handle = content
         to_user = to_proto.get_or_create(to_id)
         if not to_user:
             return reply(f"Couldn't find {to_proto.PHRASE} user {handle}")
 
-        from_proto = from_user.__class__
-
         if not to_user.obj:
             # doesn't exist
             return reply(f"Couldn't find {to_proto.PHRASE} user {handle}")

tests/test_dms.py

@@ -1,14 +1,17 @@
 """Unit tests for dms.py."""
 from unittest import mock
 
+from atproto import ATProto
 from common import memcache
 import dms
 from dms import maybe_send, receive
+import ids
 from models import DM, Follower, Object
 from web import Web
 
 from oauth_dropins.webutil.flask_util import NotModified
 from .testutil import ExplicitEnableFake, Fake, OtherFake, TestCase
+from .test_atproto import DID_DOC
 
 DM_EEFAKE_ALICE_REQUESTS_OTHER_BOB = {
     'objectType': 'note',
@@ -292,7 +295,6 @@ def test_receive_handle_request_rate_limit(self):
             ExplicitEnableFake.sent)
         self.assertEqual(3, memcache.get('dm-user-requests-eefake-eefake:alice'))
 
-
     def test_receive_handle_wrong_protocol(self):
         self.make_user(id='other.brid.gy', cls=Web)
 
@@ -307,3 +309,15 @@ def test_receive_handle_wrong_protocol(self):
         self.assertEqual([], ExplicitEnableFake.sent)
         self.assertEqual([], OtherFake.sent)
         self.assertEqual([], Fake.sent)
+
+    @mock.patch('ids.translate_handle', side_effect=ValueError('nope'))
+    def test_receive_handle_not_supported_in_target_protocol(self, _):
+        alice, bob = self.make_alice_bob()
+        obj = Object(our_as1=DM_EEFAKE_ALICE_REQUESTS_OTHER_BOB)
+
+        self.assertEqual(('OK', 200), receive(from_user=alice, obj=obj))
+        self.assertEqual(
+            [('https://other.brid.gy/#?-dm-eefake:alice-2022-01-02T03:04:05+00:00',
+              'eefake:alice:target')],
+            ExplicitEnableFake.sent)
+        self.assertEqual([], OtherFake.sent)