Fix bug with nil interface return & add test

roomserver/internal/query/query.go

@@ -868,7 +868,11 @@ func (r *Queryer) QueryRoomInfo(ctx context.Context, roomID spec.RoomID) (*types
 }
 
 func (r *Queryer) CurrentStateEvent(ctx context.Context, roomID spec.RoomID, eventType string, stateKey string) (gomatrixserverlib.PDU, error) {
-	return r.DB.GetStateEvent(ctx, roomID.String(), string(eventType), "")
+	res, err := r.DB.GetStateEvent(ctx, roomID.String(), string(eventType), "")
+	if res == nil {
+		return nil, err
+	}
+	return res, err
 }
 
 func (r *Queryer) UserJoinedToRoom(ctx context.Context, roomNID types.RoomNID, userID spec.UserID) (bool, error) {

roomserver/internal/query/query_test.go

@@ -18,10 +18,16 @@ import (
 	"context"
 	"encoding/json"
 	"testing"
+	"time"
 
+	"github.com/matrix-org/dendrite/internal/caching"
+	"github.com/matrix-org/dendrite/internal/sqlutil"
+	"github.com/matrix-org/dendrite/roomserver/storage"
 	"github.com/matrix-org/dendrite/roomserver/types"
+	"github.com/matrix-org/dendrite/setup/config"
 	"github.com/matrix-org/dendrite/test"
 	"github.com/matrix-org/gomatrixserverlib"
+	"github.com/matrix-org/gomatrixserverlib/spec"
 )
 
 // used to implement RoomserverInternalAPIEventDB to test getAuthChain
@@ -155,3 +161,30 @@ func TestGetAuthChainMultiple(t *testing.T) {
 		t.Fatalf("returnedIDs got '%v', expected '%v'", returnedIDs, expectedIDs)
 	}
 }
+
+func mustCreateDatabase(t *testing.T, dbType test.DBType) (storage.Database, func()) {
+	conStr, close := test.PrepareDBConnectionString(t, dbType)
+	caches := caching.NewRistrettoCache(8*1024*1024, time.Hour, caching.DisableMetrics)
+	cm := sqlutil.NewConnectionManager(nil, config.DatabaseOptions{})
+	db, err := storage.Open(context.Background(), cm, &config.DatabaseOptions{ConnectionString: config.DataSource(conStr)}, caches)
+	if err != nil {
+		t.Fatalf("failed to create Database: %v", err)
+	}
+	return db, close
+}
+
+func TestCurrentEventIsNil(t *testing.T) {
+	test.WithAllDatabases(t, func(t *testing.T, dbType test.DBType) {
+		db, close := mustCreateDatabase(t, dbType)
+		defer close()
+		querier := Queryer{
+			DB: db,
+		}
+
+		roomID, _ := spec.NewRoomID("!room:server")
+		event, _ := querier.CurrentStateEvent(context.Background(), *roomID, spec.MRoomMember, "@user:server")
+		if event != nil {
+			t.Fatal("Event should equal nil, most likely this is failing because the interface type is not nil, but the value is.")
+		}
+	})
+}