Add tests for UpdateRelations (#2999)

This also fixes an issue regarding updates to relations for invalid
events, which could result in us retrying said event over and over
again, if we fail to unmarshal the event to
`gomatrixserverlib.RelationContent`, this was discovered by
`@sleroq:virto.community`

syncapi/storage/shared/storage_consumer.go

@@ -567,9 +567,14 @@ func (d *Database) ReIndex(ctx context.Context, limit, afterID int64) (map[int64
 }
 
 func (d *Database) UpdateRelations(ctx context.Context, event *gomatrixserverlib.HeaderedEvent) error {
+	// No need to unmarshal if the event is a redaction
+	if event.Type() == gomatrixserverlib.MRoomRedaction {
+		return nil
+	}
 	var content gomatrixserverlib.RelationContent
 	if err := json.Unmarshal(event.Content(), &content); err != nil {
-		return fmt.Errorf("json.Unmarshal: %w", err)
+		logrus.WithError(err).Error("unable to unmarshal relation content")
+		return nil
 	}
 	switch {
 	case content.Relations == nil:
@@ -578,8 +583,6 @@ func (d *Database) UpdateRelations(ctx context.Context, event *gomatrixserverlib
 		return nil
 	case content.Relations.RelationType == "":
 		return nil
-	case event.Type() == gomatrixserverlib.MRoomRedaction:
-		return nil
 	default:
 		return d.Writer.Do(d.DB, nil, func(txn *sql.Tx) error {
 			return d.Relations.InsertRelation(

syncapi/syncapi_test.go

@@ -10,11 +10,13 @@ import (
 	"testing"
 	"time"
 
-	"github.com/matrix-org/dendrite/syncapi/routing"
 	"github.com/matrix-org/gomatrixserverlib"
 	"github.com/nats-io/nats.go"
 	"github.com/tidwall/gjson"
 
+	"github.com/matrix-org/dendrite/syncapi/routing"
+	"github.com/matrix-org/dendrite/syncapi/storage"
+
 	"github.com/matrix-org/dendrite/clientapi/producers"
 	"github.com/matrix-org/dendrite/roomserver"
 	"github.com/matrix-org/dendrite/roomserver/api"
@@ -1074,6 +1076,90 @@ func testContext(t *testing.T, dbType test.DBType) {
 	}
 }
 
+func TestUpdateRelations(t *testing.T) {
+	testCases := []struct {
+		name         string
+		eventContent map[string]interface{}
+		eventType    string
+	}{
+		{
+			name: "empty event content should not error",
+		},
+		{
+			name: "unable to unmarshal event should not error",
+			eventContent: map[string]interface{}{
+				"m.relates_to": map[string]interface{}{
+					"event_id": map[string]interface{}{}, // this should be a string and not struct
+				},
+			},
+		},
+		{
+			name: "empty event ID is ignored",
+			eventContent: map[string]interface{}{
+				"m.relates_to": map[string]interface{}{
+					"event_id": "",
+				},
+			},
+		},
+		{
+			name: "empty rel_type is ignored",
+			eventContent: map[string]interface{}{
+				"m.relates_to": map[string]interface{}{
+					"event_id": "$randomEventID",
+					"rel_type": "",
+				},
+			},
+		},
+		{
+			name:      "redactions are ignored",
+			eventType: gomatrixserverlib.MRoomRedaction,
+			eventContent: map[string]interface{}{
+				"m.relates_to": map[string]interface{}{
+					"event_id": "$randomEventID",
+					"rel_type": "m.replace",
+				},
+			},
+		},
+		{
+			name: "valid event is correctly written",
+			eventContent: map[string]interface{}{
+				"m.relates_to": map[string]interface{}{
+					"event_id": "$randomEventID",
+					"rel_type": "m.replace",
+				},
+			},
+		},
+	}
+
+	ctx := context.Background()
+
+	alice := test.NewUser(t)
+	room := test.NewRoom(t, alice)
+
+	test.WithAllDatabases(t, func(t *testing.T, dbType test.DBType) {
+		base, shutdownBase := testrig.CreateBaseDendrite(t, dbType)
+		t.Cleanup(shutdownBase)
+		db, err := storage.NewSyncServerDatasource(base, &base.Cfg.SyncAPI.Database)
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		for _, tc := range testCases {
+			t.Run(tc.name, func(t *testing.T) {
+				evType := "m.room.message"
+				if tc.eventType != "" {
+					evType = tc.eventType
+				}
+				ev := room.CreateEvent(t, alice, evType, tc.eventContent)
+				err = db.UpdateRelations(ctx, ev)
+				if err != nil {
+					t.Fatal(err)
+				}
+			})
+		}
+	})
+}
+
 func syncUntil(t *testing.T,
 	base *base.BaseDendrite, accessToken string,
 	skip bool,