Fix 'Outbound federation will ignore a missing event with bad JSON for room version 6' (#152)

This test got blacklisted for the release of Synapse 1.37.1.

We can't assume that homeservers will process inbound federation events synchronously.

In this particular case we replace the check for errors in /send response with a check that if we send a new event that references the expected rejected event we'll see a request for that event come in.

c.f. matrix-org/synapse#10275 and matrix-org/sytest#1061

Author: richvdh

tests/federation_room_get_missing_events_test.go

@@ -1,5 +1,3 @@
-// +build !synapse_blacklist
-
 package tests
 
 import (
@@ -28,8 +26,12 @@ import (
 // To test this we need to:
 // * Add an event with "bad" data into the room history, but don't send it.
 // * Add a "good" event into the room history and send it.
-// * The homeserver attempts to get the missing event (with the bad data).
-// * Ensure that fetching the event results in an error.
+// * wait for the homeserver to attempt to get the missing event (with the bad data).
+//   (The homeserver should reject the "good" event.)
+// * To check the good event was rejected, send another valid event pointing at
+//   the first "good" event, and wait for a call to `/get_missing_events` for
+//   that event (thus proving that the homeserver rejected the good event).
+//
 // sytest: Outbound federation will ignore a missing event with bad JSON for room version 6
 func TestOutboundFederationIgnoresMissingEventWithBadJSONForRoomVersion6(t *testing.T) {
 	deployment := Deploy(t, b.BlueprintAlice)
@@ -43,6 +45,13 @@ func TestOutboundFederationIgnoresMissingEventWithBadJSONForRoomVersion6(t *test
 	cancel := srv.Listen()
 	defer cancel()
 
+	// register a handler for /get_missing_events, via a shim so that we can
+	// behave differently as the test progresses.
+	var onGetMissingEvents func(w http.ResponseWriter, req *http.Request)
+	srv.Mux().HandleFunc("/_matrix/federation/v1/get_missing_events/{roomID}", func(w http.ResponseWriter, req *http.Request) {
+		onGetMissingEvents(w, req)
+	}).Methods("POST")
+
 	ver := gomatrixserverlib.RoomVersionV6
 	charlie := srv.UserID("charlie")
 	room := srv.MustMakeRoom(t, ver, federation.InitialRoomEvents(ver, charlie))
@@ -87,6 +96,7 @@ func TestOutboundFederationIgnoresMissingEventWithBadJSONForRoomVersion6(t *test
 	}
 	room.AddEvent(signedBadEvent)
 
+	// send the first "good" event, referencing the broken event as a prev_event
 	sentEvent := srv.MustCreateEvent(t, room, b.Event{
 		Type:   "m.room.message",
 		Sender: charlie,
@@ -97,7 +107,7 @@ func TestOutboundFederationIgnoresMissingEventWithBadJSONForRoomVersion6(t *test
 	room.AddEvent(sentEvent)
 
 	waiter := NewWaiter()
-	srv.Mux().HandleFunc("/_matrix/federation/v1/get_missing_events/{roomID}", func(w http.ResponseWriter, req *http.Request) {
+	onGetMissingEvents = func(w http.ResponseWriter, req *http.Request) {
 		defer waiter.Finish()
 		must.MatchRequest(t, req, match.HTTPRequest{
 			JSON: []match.JSON{
@@ -116,7 +126,7 @@ func TestOutboundFederationIgnoresMissingEventWithBadJSONForRoomVersion6(t *test
 		responseBytes, err = json.Marshal(&res)
 		must.NotError(t, "failed to marshal response", err)
 		w.Write(responseBytes)
-	}).Methods("POST")
+	}
 
 	fedClient := srv.FederationClient(deployment)
 	resp, err := fedClient.SendTransaction(context.Background(), gomatrixserverlib.Transaction{
@@ -131,9 +141,45 @@ func TestOutboundFederationIgnoresMissingEventWithBadJSONForRoomVersion6(t *test
 	if len(resp.PDUs) != 1 {
 		t.Fatalf("got %d errors, want 1", len(resp.PDUs))
 	}
-	pduRes, ok := resp.PDUs[sentEvent.EventID()]
+	_, ok := resp.PDUs[sentEvent.EventID()]
 	if !ok {
 		t.Fatalf("wrong PDU returned from send transaction, got %v want %s", resp.PDUs, sentEvent.EventID())
 	}
-	must.NotEqualStr(t, pduRes.Error, "", "wanted an error string for pdu but was blank")
+
+	// older versions of Synapse returned an error for the 'good' PDU; nowadays
+	// it just ignores it, so we need to send another event referring to the
+	// first one and check that we get a /get_missing_events request.
+
+	message3 := srv.MustCreateEvent(t, room, b.Event{
+		Type:   "m.room.message",
+		Sender: charlie,
+		Content: map[string]interface{}{
+			"body": "Message 3",
+		},
+	})
+	room.AddEvent(message3)
+
+	waiter = NewWaiter()
+	onGetMissingEvents = func(w http.ResponseWriter, req *http.Request) {
+		must.MatchRequest(t, req, match.HTTPRequest{
+			JSON: []match.JSON{
+				match.JSONKeyEqual("earliest_events", []interface{}{latestEvent.EventID()}),
+				match.JSONKeyEqual("latest_events", []interface{}{message3.EventID()}),
+			},
+		})
+		defer waiter.Finish()
+
+		// we don't really care what we return here, so just return an empty body.
+		w.WriteHeader(200)
+		w.Write([]byte("{}"))
+	}
+
+	resp, err = fedClient.SendTransaction(context.Background(), gomatrixserverlib.Transaction{
+		TransactionID: "t2",
+		Destination:   gomatrixserverlib.ServerName("hs1"),
+		PDUs: []json.RawMessage{
+			message3.JSON(),
+		},
+	})
+	waiter.Wait(t, 5*time.Second)
 }