Jake task to continously monitor the javascript and less files for the project, and rebuild them as necessary

watch.jake

desc('Continously monitors the javascript and less files for the project, and rebuilds them as necessary');
task('watch', ['build'], function () {
	// Recursively watch files with a callback
	var fs = require('fs');
	var files = [];

	var findFilesAndWatch = function (path) {
		fs.stat(path, function (err, stats) {
			if (err) {
				return false;
			}
			if (stats.isFile()) {
				files.push(path);
				fs.watchFile(path, changeCallbackFactory(path));
			}
			else if (stats.isDirectory()) {
				fs.readdir(path, function (err, dirListing) {
					if (err) {
						return log.fatal(err);
					}
					for (var f in dirListing) {
						findFilesAndWatch(path + '/' + dirListing[f]);
					}
				});
			}
		});
	};

	var changeCallbackFactory = function (file) {
		return function (cur, prev) {
			if (cur.mtime > prev.mtime) {
				stopWatch();
				var fileTask = jake.Task[file];
				if (fileTask) {
					fileTask.modTime = cur.mtime;
				}
				jake.Task['build'].reenable(true);
				jake.Task['build'].invoke();
				startWatch();
			}
		};
	};

	var startWatch = function () {
		for (var i = 0; i < files.length; i++) {
			fs.watchFile(files[i], changeCallbackFactory(files[i]));
		}
	};
	var stopWatch = function () {
		for (var i = 0; i < files.length; i++) {
			fs.unwatchFile(files[i]);
		}
	};

	findFilesAndWatch('themes');
}, {async: true});

The more I think about it, the more it makes sense to do it so you can set up file tasks as dependencies for the watch task. Then I could have it just walk the dependency tree so any files those tasks depend on get watched automatically.

The one issue I've thought of is that if any of those tasks fail (e.g. a LESS/RequireJS compilation task fails because of a syntax error), then the process exits because of the uncaught exception rather than just printing the error and continuing to run. Should I just modify Program.handleErr so it emits an event that you can subscribe to, and if a listener returns true then cancel the exit process?

Once I get a solution to that problem figured out I think I'll merge everything into a nice generic solution.

If you're talking about child processes, have a look at the new createExec stuff. It pretty much does exactly what you're describing. :)

Similar I think, but I'm not talking about child processes, I'm talking about invoking tasks. The most important feature I'd need to add is something like the "breakOnError" option for .invoke, although events similar to createExec (especially error) would be nice too. I suppose I could just use createExec to call "jake [subTaskName]", but that seems pretty fragile. - Adam Pflug

…

On Monday, June 4, 2012 at 12:17 PM, Matthew Eernisse wrote: If you're talking about child processes, have a look at the new createExec stuff. It pretty much does exactly what you're describing. :) --- Reply to this email directly or view it on GitHub: https://gist.github.com/2830614

Gotcha. The obvious path here is to make Tasks even more evented. Right now they fire "complete" when done, and errors are handled by a generic uncaughtException handler. I can add a "error" event, which can be handled by a specific handler or fall back to the generic one if nothing is set. Would that fix you up?

All right, this is in master. Just do someTask.addListener('error', function (e) {}); and call via invoke. If you don't set an explicit listener, it's handled the way it's always been. Let me know if this works for you.

Yea that works for me, thanks. On vacation in Italy for the next 2 weeks, but I'll work on this when I get back.

…

Sent from my iPad

On Jun 9, 2012, at 11:34 PM, Matthew ***@***.*** wrote: All right, this is in master. Just do someTask.addListener('error', function (e) {}); and call via `invoke`. If you don't set an explicit listener, it's handled the way it's always been. Let me know if this works for you. --- Reply to this email directly or view it on GitHub: https://gist.github.com/2830614