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");
  });
});