Delete compiled JS files when the source Coffee file gets deleted on a grunt watch.

Gruntfile-with-coffee-delete.coffee

module.exports = (grunt) ->

    coffeeDir = 'coffee/'
    jsDir = 'project/'

    grunt.initConfig
        coffee:
            project:
                expand: true
                cwd: coffeeDir
                src: ['*.coffee', '**/*.coffee']
                dest: jsDir
                ext: '.js'
                options:
                    bare: true
        watch:
            coffee:
                files: ['coffee/*.coffee', 'coffee/**/*.coffee']
                tasks: ['coffee']

    grunt.event.on 'watch', (action, filepath) ->
        # Delete compiled .js file of deleted source .coffee file.
        if action == 'deleted' and grunt.file.exists jsFile
            filepath = filepath.replace coffeeDir, ''
            jsFile = jsDir + filepath.replace /\.coffee$/, '.js'
            grunt.file.delete jsFile
            grunt.log.ok 'File ' + jsFile + ' deleted'

    grunt.loadNpmTasks task for task in ['grunt-contrib-coffee', 'grunt-contrib-watch']

    grunt.registerTask 'default', ['watch']