Method groupBy

packages/webpack-cli/src/webpack-cli.ts:1341–1351

(xs: Problem[], key: K)

    if (problems) {
      const groupBy = <K extends keyof Problem & StringsKeys<Problem>>(xs: Problem[], key: K) =>
        xs.reduce(
          (rv, problem) => {
            const path = problem[key];

            (rv[path] ||= []).push(problem);

            return rv;
          },
          {} as Record<string, Problem[]>,
        );
      const problemsByPath = groupBy<"path">(problems, "path");

      for (const path in problemsByPath) {