message: Require builders be instantiated in RecordSource
diff: @@ -49,6 +49,10 @@ export abstract class RecordSource<
  protected _keyMap?: RecordKeyMap;
  protected _schema: RecordSchema;
  + // Unlike in `Source`, builders will always be set
  + protected _queryBuilder!: QB;
  + protected _transformBuilder!: TB;
  +
  constructor(settings: RecordSourceSettings<QO, TO, QB, TB>) {
  const autoActivate =
  settings.autoActivate === undefined || settings.autoActivate;
  @@ -108,6 +112,14 @@ export abstract class RecordSource<
  return this._keyMap;
  }
  + get queryBuilder(): QB {
  + return this._queryBuilder;
  + }
  +
  + get transformBuilder(): TB {
  + return this._transformBuilder;
  + }
  +
  /**
  * Upgrade source as part of a schema upgrade.
  */
  