handle minification failure gracefully

Fixes: gruntjs#409

Whenever the minification of a file fails, the task fails with the
error 'min' is not available in 'undefined'.

This patch allows the task to continue to the next file without
making any changes to the contents of the file in the destination.
Also, this introduces a new configuration option `skipErrors`, so
that the users can specify that in the task level options to override
the default behaviour.

Gruntfile.js

@@ -412,6 +412,14 @@ module.exports = function(grunt) {
             max_line_len: 55
           }
         }
+      },
+      fail_to_minify: {
+        options: {
+          skipErrors: true
+        },
+        files: {
+          'tmp/fail_to_minify.js': ['test/fixtures/src/fail_to_minify.js']
+        }
       }
     },
 

tasks/uglify.js

@@ -53,7 +53,8 @@ module.exports = function(grunt) {
       mangle: {},
       beautify: false,
       report: 'min',
-      ie8: false
+      ie8: false,
+      skipErrors: grunt.option('force') || false
     });
 
     var footer = normalizeLf(options.footer);
@@ -138,29 +139,38 @@ module.exports = function(grunt) {
 
       // Minify files, warn and fail on error.
       var result;
+      var isFailed = false;
+
       try {
         result = uglify.minify(availableFiles, f.dest, options);
       } catch (e) {
-        console.log(e);
-        err = new Error('Uglification failed.');
-        if (e.message) {
-          err.message += '\n' + e.message + '. \n';
-          if (e.line) {
-            err.message += 'Line ' + e.line + ' in ' + availableFiles + '\n';
-          }
-        }
+        err = new Error(e.message + ' in line ' + e.line + '\n');
         err.origError = e;
-        grunt.log.warn('Uglifying source ' + chalk.cyan(availableFiles) + ' failed.');
-        grunt.fail.warn(err);
+        if (options['skipErrors']) {
+          grunt.log.error('Uglifying source ' + chalk.cyan(availableFiles) + ' failed.' + (options['skipErrors'] ? ' Skipping...' : ''));
+          grunt.log.error(err);
+        } else {
+          grunt.log.error('Uglifying source ' + chalk.cyan(availableFiles) + ' failed.');
+          grunt.fail.fatal(err);
+        }
+        isFailed = true;
       }
 
-      // Concat minified source + footer
-      var output = result.min + footer;
-
       var unCompiledJSString = availableFiles.map(function (file) {
         return grunt.file.read(file);
       }).join('');
 
+      // If the minifying fails, use the actual string as it is
+      if (isFailed) {
+        result = {
+          min: unCompiledJSString,
+          max: unCompiledJSString
+        };
+      }
+
+      // Concat minified source + footer
+      var output = isFailed ? unCompiledJSString : (result.min + footer);
+
       // Write the destination file.
       grunt.file.write(f.dest, output);
 

test/fixtures/expected/fail_to_minify.js

@@ -0,0 +1,8 @@
+// Ideally this comment should get removed
+
+function failToMinify() {
+  var @@name = 1;
+}
+
+
+/* This too */

test/fixtures/src/fail_to_minify.js

@@ -0,0 +1,8 @@
+// Ideally this comment should get removed
+
+function failToMinify() {
+  var @@name = 1;
+}
+
+
+/* This too */

test/uglify_test.js

@@ -21,6 +21,7 @@ exports.contrib_uglify = {
       'compress_mangle_banner.js',
       'compress_mangle_beautify.js',
       'compress_mangle_except.js',
+      'fail_to_minify.js',
       'multifile.js',
       'wrap.js',
       'maxLineLen.js',