Gulpfile.js

"use strict";

const plumber = require("gulp-plumber");
const through = require("through2");
const chalk = require("chalk");
const newer = require("gulp-newer");
const babel = require("gulp-babel");
const watch = require("gulp-watch");
const gutil = require("gulp-util");
const gulp = require("gulp");
const path = require("path");

const base = path.join(__dirname, "packages");
const scripts = "./packages/*/src/**/*.js";

function swapSrcWithLib(srcPath) {
  const parts = srcPath.split(path.sep);
  parts[1] = "lib";
  return parts.join(path.sep);
}

gulp.task("default", ["build"]);

gulp.task("build", function () {
  return gulp.src(scripts, { base: base })
    .pipe(plumber({
      errorHandler: function (err) {
        gutil.log(err.stack);
      },
    }))
    .pipe(newer({
      dest: base,
      map: swapSrcWithLib,
    }))
    .pipe(through.obj(function (file, enc, callback) {
      gutil.log("Compiling", "'" + chalk.cyan(file.relative) + "'...");
      callback(null, file);
    }))
    .pipe(babel())
    .pipe(through.obj(function (file, enc, callback) {
      // Passing 'file.relative' because newer() above uses a relative path and this keeps it consistent.
      file.path = path.resolve(file.base, swapSrcWithLib(file.relative));
      callback(null, file);
    }))
    .pipe(gulp.dest(base));
});

gulp.task("watch", ["build"], function () {
  watch(scripts, { debounceDelay: 200 }, function () {
    gulp.start("build");
  });
});