less task hangs silently with sourceMap: true when EPERM expected

[DimitarChristoff]

Interesting issue. Using a perforce repo, the files need to be unlocked before building. sometimes you forget and the task throws an EPERM error:

Writing web/assets/style.min.css...ERROR
Fatal error: Unable to write "web/assets/style.min.css" file (Error code: EPERM).�

that's caught and the task exits, as expected.

When sourceMap: true is set, relating to https://github.com/gruntjs/grunt-contrib-less/blob/master/tasks/less.js#L71 and grunt.file.write(), it just hangs.

With --verbose, it catches it:

Writing web/assets/style.min.css.map...ERROR

BUT: it does not exit the process and just hangs. This also affects watch tasks etc.

[DimitarChristoff]

this should probably be caught by the grunt/file.js grunt.file - https://github.com/gruntjs/grunt/blob/master/lib/grunt/file.js#L300 but it's just not working.

adding this fixes it:

              try {
                grunt.file.write(sourceMapFilename, output.map);
                grunt.log.writeln('File ' + chalk.cyan(options.sourceMapFilename) + ' created.');
              }
              catch(err){
                nextFileObj(err);
              }

Writing web/assets/style.min.css.map...ERROR
Writing web/assets/style.min.css...ERROR
Fatal error: Unable to write "web/assets/style.min.css" file (Error code: EPERM).�