grafana/public/app/plugins/datasource/loki/responseUtils.ts

import { DataFrame, Labels } from '@grafana/data';

export function dataFrameHasLokiError(frame: DataFrame): boolean {
  const labelSets: Labels[] = frame.fields.find((f) => f.name === 'labels')?.values.toArray() ?? [];
  return labelSets.some((labels) => labels.__error__ !== undefined);
}