File rule without a target

[aidanhs]

Sometimes I want to be able to run some operation on a file but not have any output, e.g. allowing me to only hint js files changed since the last run.

I can currently do this with something like

var jshint = 'node_modules/jshint/bin/jshint -c .jshintrc';
function rep(name) {
  name.replace(/\.hint\.js$/, '.js');
}
rule(/tmp.*\.hint\.js$/, rep, { async: true }, function () {
  var ee = jake.createExec(jshint + ' ' + this.source, { interactive: true });
  ee.addListener('cmdEnd', (function () {
    jake.mkdirP(path.dirname(this.name));
    jake.cpR(this.source, this.name, { silent: true });
    console.log('end');
    complete();
  }).bind(this));
  ee.addListener('error', function () {
    console.log('err');
  });
  ee.run();
});

(untested, but gives the idea)

Needless to say, I'd prefer something a little less crazy. Some observations:

• I have to set 'interactive: true' to get error output from jshint - printStdout and printStderr don't seem to work? They do for jake.exec.
• I could use exec if it revealed that the command errored e.g. by
  • an argument to the callback in async/a property of the exec object in sync mode
  • simply not executing any more steps in a rule
• The documentation doesn't say in which order 'cmdEnd' and 'error' are fired so I had to experiment (discovering 'error' comes first).
• "If breakOnError is set to true, the Exec object will emit and 'error' event after the first error, and stop any further execution." - 'execution' is unclear to me. Will it stop after this rule (like exec)? After all events (including 'cmdEnd') have been fired? Turns out it immediately halts after the error event (which is unintuitive given the 'continue running' behaviour of an error during exec!).

Coming back to the issue title, I'd like to get rid of my tmp directory handling and give rules with no target, e.g.

var srcfiles = glob('**/*.js');
rule(null, srcfiles, function () {
  // hinting
})

'null' rules would always be run so I'd envisage their main value as being inside tasks (i.e. a 'hint' task with the code above inside it). I don't know how rules currently behave when called from inside tasks, so possibly this is easier said than done.

[aidanhs]

I've deleted a previous comment about silent: true, it was unrelated.

[mde]

Wow, there's a lot going on here. :) First, to answer your question about output from the Exec object, having a look at how jake.exec is implemented will give you some idea of why output works the way it does: https://github.com/jakejs/jake/blob/master/lib/utils/index.js#L114 It's really just a thin wrapper around Exec -- just listened for the 'stdout' events and logs them out. jake.exec is really just a super-minimal way to run a bunch of shell commands and bail out if something goes wrong.

For what you're trying to do, it might make more sense to take advantage of the default FileTask behavior -- it will only run when one if its prereq files has changed. There's nothing passed in to indicate which one changed (it bails as soon as it finds a change in any item, which is generally what you want), but you can still iterate the original list and compare the "modTime" props to see which ones to lint.

I did it with a Jakefile like this:

var list = new jake.FileList(['**/*.js']);

file('monitor.txt', list.toArray(), function () {
  var self = this;
  console.log('Something changed');
  list.forEach(function (key) {
    var ft = jake.Task[key];
    if (ft.modTime > self.modTime) {
      console.log(ft.name);
    }
  });
  // Update the mod-time on the monitoring file
  fs.writeFileSync('monitor.txt', '');
});

task('default', ['monitor.txt']);