gulpfile-error-handling.js

var gulp = require('gulp');
var gutil = require('gulp-util');
var jshint = require('gulp-jshint');

// Command line option:
//  --fatal=[warning|error|off]
var fatalLevel = require('yargs').argv.fatal;

var ERROR_LEVELS = ['error', 'warning'];

// Return true if the given level is equal to or more severe than
// the configured fatality error level.
// If the fatalLevel is 'off', then this will always return false.
// Defaults the fatalLevel to 'error'.
function isFatal(level) {
   return ERROR_LEVELS.indexOf(level) <= ERROR_LEVELS.indexOf(fatalLevel || 'error');
}

// Handle an error based on its severity level.
// Log all levels, and exit the process for fatal levels.
function handleError(level, error) {
   gutil.log(error.message);
   if (isFatal(level)) {
      process.exit(1);
   }
}

// Convenience handler for error-level errors.
function onError(error) { handleError.call(this, 'error', error);}
// Convenience handler for warning-level errors.
function onWarning(error) { handleError.call(this, 'warning', error);}

var testfiles = ['error.js', 'warning.js'];

// Task that emits an error that's treated as a warning.
gulp.task('warning', function() {
   gulp.src(testfiles).
      pipe(jshint()).
      pipe(jshint.reporter('fail')).
      on('error', onWarning);
});

// Task that emits an error that's treated as an error.
gulp.task('error', function() {
   gulp.src(testfiles).
      pipe(jshint()).
      pipe(jshint.reporter('fail')).
      on('error', onError);
});

gulp.task('watch', function() {
   // By default, errors during watch should not be fatal.
   fatalLevel = fatalLevel || 'off';
   gulp.watch(testfiles, ['error']);
});

gulp.task('default', ['watch']);