emit an error when it fails to load an ESLint plugin

fix #185

CHANGELOG.md

@@ -7,6 +7,7 @@
 * Use [`Buffer.from(<string>)`](https://nodejs.org/api/buffer.html#buffer_class_method_buffer_from_string_encoding) instead of the deprecated [`new Buffer(<string>)`](https://nodejs.org/dist/latest-v8.x/docs/api/buffer.html#buffer_new_buffer_string_encoding)
   * Note that `Buffer.from` is only available on Node.js >= [4.5.0](https://nodejs.org/en/blog/release/v4.5.0/).
 * Bump [`eslint`](https://github.com/eslint/eslint) dependency to [`^4.0.0`](http://eslint.org/blog/2017/06/eslint-v4.0.0-released)
+* Emit a [`PluginError`](https://github.com/gulpjs/gulp-util#new-pluginerrorpluginname-message-options) when it fails to load an [ESLint plugin](http://eslint.org/docs/user-guide/configuring#configuring-plugins)
 
 ## 3.0.1
 

index.js

@@ -15,19 +15,6 @@ function gulpEslint(options) {
 	options = util.migrateOptions(options) || {};
 	const linter = new CLIEngine(options);
 
-	function verify(str, filePath) {
-		const result = linter.executeOnText(str, filePath).results[0];
-		// Note: Fixes are applied as part of "executeOnText".
-		// Any applied fix messages have been removed from the result.
-
-		if (options.quiet) {
-			// ignore warnings
-			return util.filterResult(result, options.quiet);
-		}
-
-		return result;
-	}
-
 	return util.transform((file, enc, cb) => {
 		const filePath = path.relative(process.cwd(), file.path);
 
@@ -57,7 +44,24 @@ function gulpEslint(options) {
 			return;
 		}
 
-		file.eslint = verify(file.contents.toString(), filePath);
+		let result;
+
+		try {
+			result = linter.executeOnText(file.contents.toString(), filePath).results[0];
+		} catch (e) {
+			cb(new PluginError('gulp-eslint', e));
+			return;
+		}
+		// Note: Fixes are applied as part of "executeOnText".
+		// Any applied fix messages have been removed from the result.
+
+		if (options.quiet) {
+			// ignore warnings
+			file.eslint =  util.filterResult(result, options.quiet);
+		} else {
+			file.eslint = result;
+		}
+
 		// Update the fixed output; otherwise, fixable messages are simply ignored.
 		if (file.eslint.hasOwnProperty('output')) {
 			file.contents = Buffer.from(file.eslint.output);

test/linting.js

@@ -106,6 +106,7 @@ describe('gulp-eslint plugin', () => {
 	it('should emit an error when it takes a steam content', done => {
 		eslint({useEslintrc: false, rules: {'strict': 'error'}})
 		.on('error', err => {
+			err.plugin.should.equal('gulp-eslint');
 			err.message.should.equal('gulp-eslint doesn\'t support vinyl files with Stream contents.');
 			done();
 		})
@@ -115,6 +116,23 @@ describe('gulp-eslint plugin', () => {
 		}));
 	});
 
+	it('should emit an error when it fails to load a plugin', done => {
+		const pluginName = 'this-is-unknown-plugin';
+		eslint({plugins: [pluginName]})
+		.on('error', err => {
+			err.plugin.should.equal('gulp-eslint');
+			err.message.should.equal(`Failed to load plugin this-is-unknown-plugin: Cannot find module 'eslint-plugin-${
+				pluginName
+			}'`);
+
+			done();
+		})
+		.end(new File({
+			path: 'test/fixtures/file.js',
+			contents: Buffer.from('')
+		}));
+	});
+
 	describe('"warnFileIgnored" option', () => {
 
 		it('when true, should warn when a file is ignored by .eslintignore', done => {