Return well_known in /login response (#4319)

... as per MSC1730.

changelog.d/4319.feature

@@ -0,0 +1 @@
+Return server data in /login response

synapse/rest/client/v1/login.py

@@ -28,6 +28,7 @@ from synapse.http.servlet import (
     parse_json_object_from_request,
     parse_string,
 )
+from synapse.rest.well_known import WellKnownBuilder
 from synapse.types import UserID, map_username_to_mxid_localpart
 from synapse.util.msisdn import phone_number_to_msisdn
 
@@ -95,6 +96,7 @@ class LoginRestServlet(ClientV1RestServlet):
         self.auth_handler = self.hs.get_auth_handler()
         self.device_handler = self.hs.get_device_handler()
         self.handlers = hs.get_handlers()
+        self._well_known_builder = WellKnownBuilder(hs)
 
     def on_GET(self, request):
         flows = []
@@ -132,16 +134,18 @@ class LoginRestServlet(ClientV1RestServlet):
             if self.jwt_enabled and (login_submission["type"] ==
                                      LoginRestServlet.JWT_TYPE):
                 result = yield self.do_jwt_login(login_submission)
-                defer.returnValue(result)
             elif login_submission["type"] == LoginRestServlet.TOKEN_TYPE:
                 result = yield self.do_token_login(login_submission)
-                defer.returnValue(result)
             else:
                 result = yield self._do_other_login(login_submission)
-                defer.returnValue(result)
         except KeyError:
             raise SynapseError(400, "Missing JSON keys.")
 
+        well_known_data = self._well_known_builder.get_well_known()
+        if well_known_data:
+            result["well_known"] = well_known_data
+        defer.returnValue((200, result))
+
     @defer.inlineCallbacks
     def _do_other_login(self, login_submission):
         """Handle non-token/saml/jwt logins
@@ -150,7 +154,7 @@ class LoginRestServlet(ClientV1RestServlet):
             login_submission:
 
         Returns:
-            (int, object): HTTP code/response
+            dict: HTTP response
         """
         # Log the request we got, but only certain fields to minimise the chance of
         # logging someone's password (even if they accidentally put it in the wrong
@@ -233,7 +237,7 @@ class LoginRestServlet(ClientV1RestServlet):
         if callback is not None:
             yield callback(result)
 
-        defer.returnValue((200, result))
+        defer.returnValue(result)
 
     @defer.inlineCallbacks
     def do_token_login(self, login_submission):
@@ -253,7 +257,7 @@ class LoginRestServlet(ClientV1RestServlet):
             "device_id": device_id,
         }
 
-        defer.returnValue((200, result))
+        defer.returnValue(result)
 
     @defer.inlineCallbacks
     def do_jwt_login(self, login_submission):
@@ -307,7 +311,7 @@ class LoginRestServlet(ClientV1RestServlet):
                 "home_server": self.hs.hostname,
             }
 
-        defer.returnValue((200, result))
+        defer.returnValue(result)
 
     def _register_device(self, user_id, login_submission):
         """Register a device for a user.

tests/utils.py

@@ -140,6 +140,9 @@ def default_config(name):
     config.rc_messages_per_second = 10000
     config.rc_message_burst_count = 10000
     config.saml2_enabled = False
+    config.public_baseurl = None
+    config.default_identity_server = None
+
     config.use_frozen_dicts = False
 
     # we need a sane default_room_version, otherwise attempts to create rooms will