running a dynamically named grunt task with grunt-contrib-watch - gruntjs

Question

Is there a way to dynamically specify the task to run based on the file changed?
In other words:
watch: {
exec: {
files: [html/*.html],
tasks: ['exec:my_exec_task:THE_FILE_THAT_CHANGED']
}
}
I can catch the watch events, but I can't run tasks from within the callback as it's "doing it wrong".
grunt.event.on('watch', function(action, filepath, target) {
if (target === 'exec') {
grunt.task.run('exec:my_exec_task:' + filepath); /* this doesn't work */
grunt.config('filepath', filepath); /* and neither does this, it's undefined in my exec task */
}
});
At least that's what the documentation says: https://github.com/gruntjs/grunt-contrib-watch#using-the-watch-event
Any ideas?

Answer 1

According to docs
The watch event is not intended for replacing the standard Grunt API for configuring and running tasks. If you're trying to run tasks from within the watch event you're more than likely doing it wrong. Please read configuring tasks.
You can't run task from event, but you can change config before task starts. Add to watch config options section spawn: false
grunt.initConfig({
watch: {
scripts: {
files: ['app/*.js'],
tasks: ['jshint:one'],
options: {
spawn: false,
},
},
},
jshint: {
one: {src: ""},
},
});
and on watch event change config "on fly"
grunt.event.on('watch', function(action, filepath) {
grunt.config('jshint.one.src', filepath);
});
after applying config that watch section will run task jahint:one.