symlink node_module dependencies on Windows

gulpfile.js

/**
 * Gulpfile.js
 * Symlinks node_module dependencies into any directory. This
 * file works on Windows and Linux machines by recursively
 * symlinking the files within a node module instead of symlinking
 * just the directory. This is vitally important as Editor's on Windows
 * do not understand Junctions and therefor will delete all the children
 * files first (i.e. the original files from the original directory), a
 * disasterous situation, especially if this is used with npm link.
 */
   
var gulp          = require('gulp'),
    clean         = require('gulp-clean'),
    path          = require('path'),
    fs            = require('graceful-fs'),
    source        = require('vinyl-source-stream'),
    through2      = require('through2'),
    prepareWrite  = require('vinyl-fs/lib/prepareWrite'),

    // Project package.json
    PACKAGE_JSON  = JSON.parse (fs.readFileSync ('./package.json')),

    // Project Structure 
    APP = {
      SRC: {
        BASE: "./src/main/webapp/js",
        DEST: "./src/main/webapp/dist",
        GLOBS: [
          "**/*.js"
        ],
        FILTER: () => APP.SRC.GLOBS.map(glob => path.join(APP.SRC.BASE, glob))
      },
      TESTS: {
        BASE: "./src/test/js",
        DEST: "./src/test/dist",
        GLOBS: [
          "**/*.js"
        ],
        FILTER: () => APP.TESTS.GLOBS.map(glob => path.join(APP.TESTS.BASE, glob))
      },
      DEPS: {
        BASE: "./node_modules",
        DEST: "./src/main/webapp/lib",
        GLOBS: Object.keys (PACKAGE_JSON.dependencies).map(dep => dep + "/**/*"),
        FILTER: () => APP.DEPS.GLOBS.map (glob => path.join(APP.DEPS.BASE, glob))
      }
    };

gulp.task ('default', ['build:deps', 'build:src']);

// Link the dependencies to the lib directory instead of requiring a copy.
gulp.task ('build:deps', function () {
  return gulp.src(APP.DEPS.FILTER(), { base: APP.DEPS.BASE})
             .pipe(symlink(APP.DEPS.DEST, {}));
});

// Just an example. Babel would go here.
gulp.task ('build:src', function () {
  return gulp.src(APP.SRC.FILTER(), { base: APP.SRC.BASE})
             .pipe(gulp.dest(APP.SRC.DEST));
});

// Clean project
gulp.task('build:clean', function () {
  return gulp.src(Object.keys(APP).map(key => APP[key]["DEST"]).filter(Boolean))
             .pipe(clean());
});

/**
 * Create a special symlink stream processor which will 
 * use junctions instead of dir on Windows. As the 'dir' symlink
 * on Windows is all but impossible to create as a User with Admin rights. 
 */
function symlink(outFolder, opt) {
  function linkFile(file, enc, cb) {
    var srcPath = file.path;
    var symType = file.isDirectory() ? ((process.platform === 'win32') ? 'junction' : 'dir') : 'file';
    prepareWrite(outFolder, file, opt, function(err, writePath) {
      if (err) {
        return cb(err);
      }
      fs.symlink(srcPath, writePath, symType, function(err) {
        if (err && err.code !== 'EEXIST') {
          return cb(err);
        }
        cb(null, file);
      });

    });
  }
  var stream = through2.obj(opt, linkFile);
  stream.resume();
  return stream;
}