gulpfile.babel.js

function patchManifest(done) {
  const tasks = countryList.map((countryName) => {
    function patchManifestByCountry() {
      return
        gulp.src(`./build/${countryName}/manifest.json`)
          .pipe(gulpJsonTransform((data) => {
            data.homepage_url = .....;
            return data;
          }))
          .pipe(gulp.dest(`./build/${countryName}/`));
    }
    // Use funciton.displayName to custom the task name
    patchManifestByCountry.displayName = `patch_${countryName}_manifest`;
    return patchManifestByCountry;
  });

  // The final task is still a anonymous function, you can fix it like above solution!
  return gulp.series(...tasks, (seriesDone) => {
    seriesDone();
    done();
  })(); 
}