Address matrix-org/dendrite#1394 bugs (#257)

* address matrix-org/dendrite#1394 bugs

* praise be the eternal linter

* address feedback

* convert other manual sync calls

* lint

Author: ShadowJonathan

internal/client/client.go

@@ -592,7 +592,7 @@ func SyncInvitedTo(userID, roomID string) SyncCheckOpt {
 	}
 }
 
-// Check that `userID` gets joined to `roomID` by inspecting the join timeline for a membership event.
+// Check that `userID` gets joined to `roomID` by inspecting the join timeline for a membership event
 func SyncJoinedTo(userID, roomID string) SyncCheckOpt {
 	return func(clientUserID string, topLevelSyncJSON gjson.Result) error {
 		// awkward wrapping to get the error message correct at the start :/
@@ -606,6 +606,29 @@ func SyncJoinedTo(userID, roomID string) SyncCheckOpt {
 	}
 }
 
+// Check that `userID` is leaving `roomID` by inspecting the timeline for a membership event, or witnessing `roomID` in `rooms.leave`
+// Note: This will not work properly with initial syncs, see https://github.com/matrix-org/matrix-doc/issues/3537
+func SyncLeftFrom(userID, roomID string) SyncCheckOpt {
+	return func(clientUserID string, topLevelSyncJSON gjson.Result) error {
+		// two forms which depend on what the client user is:
+		// - passively viewing a membership for a room you're joined in
+		// - actively leaving the room
+		if clientUserID == userID {
+			// active
+			events := topLevelSyncJSON.Get("rooms.leave." + GjsonEscape(roomID))
+			if !events.Exists() {
+				return fmt.Errorf("no leave section for room %s", roomID)
+			} else {
+				return nil
+			}
+		}
+		// passive
+		return SyncTimelineHas(roomID, func(ev gjson.Result) bool {
+			return ev.Get("type").Str == "m.room.member" && ev.Get("state_key").Str == userID && ev.Get("content.membership").Str == "leave"
+		})(clientUserID, topLevelSyncJSON)
+	}
+}
+
 // Calls the `check` function for each global account data event, and returns with success if the
 // `check` function returns true for at least one event.
 func SyncGlobalAccountDataHas(check func(gjson.Result) bool) SyncCheckOpt {

tests/csapi/sync_test.go

@@ -0,0 +1,84 @@
+package csapi_tests
+
+import (
+	"testing"
+
+	"github.com/matrix-org/complement/internal/b"
+	"github.com/matrix-org/complement/internal/client"
+)
+
+// Observes "first bug" from https://github.com/matrix-org/dendrite/pull/1394#issuecomment-687056673
+func TestCumulativeJoinLeaveJoinSync(t *testing.T) {
+	deployment := Deploy(t, b.BlueprintOneToOneRoom)
+	defer deployment.Destroy(t)
+
+	alice := deployment.Client(t, "hs1", "@alice:hs1")
+	bob := deployment.Client(t, "hs1", "@bob:hs1")
+
+	roomID := bob.CreateRoom(t, map[string]interface{}{
+		"preset": "public_chat",
+	})
+
+	var since string
+
+	// Get floating next_batch from before joining at all
+	_, since = alice.MustSync(t, client.SyncReq{TimeoutMillis: "0"})
+
+	alice.JoinRoom(t, roomID, nil)
+
+	// This assumes that sync does not have side-effects in servers.
+	//
+	// The alternative would be to sleep, but that is not acceptable here.
+	sinceJoin := alice.MustSyncUntil(t, client.SyncReq{}, client.SyncJoinedTo(alice.UserID, roomID))
+
+	alice.LeaveRoom(t, roomID)
+
+	sinceLeave := alice.MustSyncUntil(t, client.SyncReq{Since: sinceJoin}, client.SyncLeftFrom(alice.UserID, roomID))
+
+	alice.JoinRoom(t, roomID, nil)
+
+	alice.MustSyncUntil(t, client.SyncReq{Since: sinceLeave}, client.SyncJoinedTo(alice.UserID, roomID))
+
+	jsonRes, _ := alice.MustSync(t, client.SyncReq{TimeoutMillis: "0", Since: since})
+	if jsonRes.Get("rooms.leave." + client.GjsonEscape(roomID)).Exists() {
+		t.Errorf("Incremental sync has joined-left-joined room showing up in leave section, this shouldnt be the case.")
+	}
+}
+
+// Observes "second bug" from https://github.com/matrix-org/dendrite/pull/1394#issuecomment-687056673
+func TestTentativeEventualJoiningAfterRejecting(t *testing.T) {
+	deployment := Deploy(t, b.BlueprintOneToOneRoom)
+	defer deployment.Destroy(t)
+
+	alice := deployment.Client(t, "hs1", "@alice:hs1")
+	bob := deployment.Client(t, "hs1", "@bob:hs1")
+
+	roomID := alice.CreateRoom(t, map[string]interface{}{
+		"preset": "public_chat",
+	})
+
+	var since string
+
+	// Get floating current next_batch
+	_, since = alice.MustSync(t, client.SyncReq{TimeoutMillis: "0"})
+
+	alice.InviteRoom(t, roomID, bob.UserID)
+
+	bob.MustSyncUntil(t, client.SyncReq{}, client.SyncInvitedTo(bob.UserID, roomID))
+
+	// This rejects the invite
+	bob.LeaveRoom(t, roomID)
+
+	// Full sync
+	jsonRes, since := bob.MustSync(t, client.SyncReq{TimeoutMillis: "0", FullState: true, Since: since})
+	if !jsonRes.Get("rooms.leave." + client.GjsonEscape(roomID)).Exists() {
+		t.Errorf("Bob just rejected an invite, it should show up under 'leave' in a full sync")
+	}
+
+	bob.JoinRoom(t, roomID, nil)
+
+	jsonRes, since = bob.MustSync(t, client.SyncReq{TimeoutMillis: "0", FullState: true, Since: since})
+	if jsonRes.Get("rooms.leave." + client.GjsonEscape(roomID)).Exists() {
+		t.Errorf("Bob has rejected an invite, but then just joined the public room anyways, it should not show up under 'leave' in a full sync %s", since)
+	}
+}