New: Support ESM w/ mjs extension where available (#214)

index.js

@@ -62,7 +62,12 @@ var parser = yargs.usage(usage, cliOptions);
 var opts = parser.argv;
 
 cli.on('require', function(name) {
-  log.info('Requiring external module', ansi.magenta(name));
+  // This is needed because interpret needs to stub the .mjs extension
+  // Without the .mjs require hook, rechoir blows up
+  // However, we don't want to show the mjs-stub loader in the logs
+  if (path.basename(name, '.js') !== 'mjs-stub') {
+    log.info('Requiring external module', ansi.magenta(name));
+  }
 });
 
 cli.on('requireFail', function(name, error) {

lib/shared/require-or-import.js

@@ -0,0 +1,32 @@
+'use strict';
+
+var pathToFileURL = require('url').pathToFileURL;
+
+var importESM;
+try {
+  // Node.js <10 errors out with a SyntaxError when loading a script that uses import().
+  // So a function is dynamically created to catch the SyntaxError at runtime instead of parsetime.
+  // That way we can keep supporting all Node.js versions all the way back to 0.10.
+  importESM = new Function('id', 'return import(id);');
+} catch (e) {
+  importESM = null;
+}
+
+function requireOrImport(path, callback) {
+  var err = null;
+  var cjs;
+  try {
+    cjs = require(path);
+  } catch (e) {
+    if (pathToFileURL && importESM && e.code === 'ERR_REQUIRE_ESM') {
+      // This is needed on Windows, because import() fails if providing a Windows file path.
+      var url = pathToFileURL(path);
+      importESM(url).then(function(esm) { callback(null, esm); }, callback);
+      return;
+    }
+    err = e;
+  }
+  process.nextTick(function() { callback(err, cjs); });
+}
+
+module.exports = requireOrImport;

lib/versioned/^3.7.0/index.js

@@ -11,9 +11,11 @@ var copyTree = require('../../shared/log/copy-tree');
 var tildify = require('../../shared/tildify');
 var logTasks = require('../../shared/log/tasks');
 var ansi = require('../../shared/ansi');
+var exit = require('../../shared/exit');
 var logEvents = require('./log/events');
 var logTasksSimple = require('./log/tasks-simple');
 var registerExports = require('../../shared/register-exports');
+var requireOrImport = require('../../shared/require-or-import');
 
 function execute(opts, env, config) {
   var tasks = opts._;
@@ -25,20 +27,25 @@ function execute(opts, env, config) {
   }
 
   // This is what actually loads up the gulpfile
-  var exported = require(env.configPath);
-  log.info('Using gulpfile', ansi.magenta(tildify(env.configPath)));
+  requireOrImport(env.configPath, function(err, exported) {
+    // Before import(), if require() failed we got an unhandled exception on the module level.
+    // So console.error() & exit() were added here to mimic the old behavior as close as possible.
+    if (err) {
+      console.error(err);
+      exit(1);
+    }
 
-  var gulpInst = require(env.modulePath);
-  logEvents(gulpInst);
+    log.info('Using gulpfile', ansi.magenta(tildify(env.configPath)));
 
-  registerExports(gulpInst, exported);
+    var gulpInst = require(env.modulePath);
+    logEvents(gulpInst);
 
-  // Always unmute stdout after gulpfile is required
-  stdout.unmute();
+    registerExports(gulpInst, exported);
 
-  process.nextTick(function() {
-    var tree;
+    // Always unmute stdout after gulpfile is required
+    stdout.unmute();
 
+    var tree;
     if (opts.tasksSimple) {
       return logTasksSimple(env, gulpInst);
     }

lib/versioned/^4.0.0-alpha.1/index.js

@@ -16,6 +16,7 @@ var logTasksSimple = require('../^4.0.0/log/tasks-simple');
 var registerExports = require('../../shared/register-exports');
 
 var copyTree = require('../../shared/log/copy-tree');
+var requireOrImport = require('../../shared/require-or-import');
 
 function execute(opts, env, config) {
 
@@ -32,16 +33,20 @@ function execute(opts, env, config) {
   logSyncTask(gulpInst, opts);
 
   // This is what actually loads up the gulpfile
-  var exported = require(env.configPath);
+  requireOrImport(env.configPath, function(err, exported) {
+    // Before import(), if require() failed we got an unhandled exception on the module level.
+    // So console.error() & exit() were added here to mimic the old behavior as close as possible.
+    if (err) {
+      console.error(err);
+      exit(1);
+    }
 
-  registerExports(gulpInst, exported);
+    registerExports(gulpInst, exported);
 
-  // Always unmute stdout after gulpfile is required
-  stdout.unmute();
+    // Always unmute stdout after gulpfile is required
+    stdout.unmute();
 
-  process.nextTick(function() {
     var tree;
-
     if (opts.tasksSimple) {
       return logTasksSimple(gulpInst.tree());
     }

lib/versioned/^4.0.0-alpha.2/index.js

@@ -17,6 +17,7 @@ var registerExports = require('../../shared/register-exports');
 
 var copyTree = require('../../shared/log/copy-tree');
 var getTask = require('../^4.0.0/log/get-task');
+var requireOrImport = require('../../shared/require-or-import');
 
 function execute(opts, env, config) {
 
@@ -33,16 +34,20 @@ function execute(opts, env, config) {
   logSyncTask(gulpInst, opts);
 
   // This is what actually loads up the gulpfile
-  var exported = require(env.configPath);
+  requireOrImport(env.configPath, function(err, exported) {
+    // Before import(), if require() failed we got an unhandled exception on the module level.
+    // So console.error() & exit() were added here to mimic the old behavior as close as possible.
+    if (err) {
+      console.error(err);
+      exit(1);
+    }
 
-  registerExports(gulpInst, exported);
+    registerExports(gulpInst, exported);
 
-  // Always unmute stdout after gulpfile is required
-  stdout.unmute();
+    // Always unmute stdout after gulpfile is required
+    stdout.unmute();
 
-  process.nextTick(function() {
     var tree;
-
     if (opts.tasksSimple) {
       tree = gulpInst.tree();
       return logTasksSimple(tree.nodes);

lib/versioned/^4.0.0/index.js

@@ -17,6 +17,7 @@ var registerExports = require('../../shared/register-exports');
 
 var copyTree = require('../../shared/log/copy-tree');
 var getTask = require('./log/get-task');
+var requireOrImport = require('../../shared/require-or-import');
 
 function execute(opts, env, config) {
 
@@ -33,16 +34,20 @@ function execute(opts, env, config) {
   logSyncTask(gulpInst, opts);
 
   // This is what actually loads up the gulpfile
-  var exported = require(env.configPath);
+  requireOrImport(env.configPath, function(err, exported) {
+    // Before import(), if require() failed we got an unhandled exception on the module level.
+    // So console.error() & exit() were added here to mimic the old behavior as close as possible.
+    if (err) {
+      console.error(err);
+      exit(1);
+    }
 
-  registerExports(gulpInst, exported);
+    registerExports(gulpInst, exported);
 
-  // Always unmute stdout after gulpfile is required
-  stdout.unmute();
+    // Always unmute stdout after gulpfile is required
+    stdout.unmute();
 
-  process.nextTick(function() {
     var tree;
-
     if (opts.tasksSimple) {
       tree = gulpInst.tree();
       return logTasksSimple(tree.nodes);

package.json

@@ -39,15 +39,15 @@
     "copy-props": "^2.0.1",
     "fancy-log": "^1.3.2",
     "gulplog": "^1.0.0",
-    "interpret": "^1.1.0",
+    "interpret": "^1.4.0",
     "isobject": "^3.0.1",
     "liftoff": "^3.1.0",
     "matchdep": "^2.0.0",
     "mute-stdout": "^1.0.0",
     "pretty-hrtime": "^1.0.0",
     "replace-homedir": "^1.0.0",
     "semver-greatest-satisfied-range": "^1.1.0",
-    "v8flags": "^3.0.1",
+    "v8flags": "^3.2.0",
     "yargs": "^7.1.0"
   },
   "devDependencies": {
@@ -62,7 +62,8 @@
     "marked-man": "^0.2.1",
     "mocha": "^3.2.0",
     "nyc": "^13.3.0",
-    "rimraf": "^2.6.1"
+    "rimraf": "^2.6.1",
+    "semver": "^5.7.1"
   },
   "keywords": [
     "build",

test/esm.js

@@ -0,0 +1,41 @@
+'use strict';
+
+var expect = require('expect');
+var fs = require('fs');
+var path = require('path');
+var semver = require('semver');
+var skipLines = require('gulp-test-tools').skipLines;
+var eraseTime = require('gulp-test-tools').eraseTime;
+var runner = require('gulp-test-tools').gulpRunner;
+
+var expectedDir = path.join(__dirname, 'expected');
+
+describe('ESM', function() {
+
+  it('prints the task list', function(done) {
+    if (semver.lt(process.version, '10.15.3')) {
+      this.skip();
+    }
+
+    var options = '--tasks --sort-tasks ' +
+      '--gulpfile ./test/fixtures/gulpfiles/gulpfile.mjs';
+    var trailingLines = 1;
+    if (!semver.satisfies(process.version, '^12.17.0 || >=13.2.0')) {
+      options += ' --experimental-modules';
+      trailingLines += 2;
+    }
+
+    runner({ verbose: false }).gulp(options).run(cb);
+
+    function cb(err, stdout, stderr) {
+      expect(err).toEqual(null);
+      expect(stderr).toMatch(/^(.*ExperimentalWarning: The ESM module loader is experimental\.\n)?$/);
+      var filepath = path.join(expectedDir, 'esm.txt');
+      var expected = fs.readFileSync(filepath, 'utf-8');
+      stdout = eraseTime(skipLines(stdout, trailingLines));
+      expect(stdout).toEqual(expected);
+      done(err);
+    }
+  });
+
+});

test/expected/esm.txt

@@ -0,0 +1,3 @@
+gulp-cli/test/fixtures/gulpfiles
+├── exported
+└── registered

test/fixtures/gulpfiles/gulpfile.mjs

@@ -0,0 +1,10 @@
+import gulp from 'gulp';
+
+function noop(cb) {
+  cb();
+}
+
+gulp.task('registered', noop);
+
+export function exported(){};
+export const string = 'no function';