Add async.tryEach

[alFReD-NSH]

This adds async.tryEach which fixes what was requested in #687. I needed something with similar requirements. My use case was that I needed to get some data, which I could get it from 3 websites(with slightly different code for each) but sometimes they go down randomly.

The name might be reconsidered. We can't use try because it's a reserved word. I couldn't think of anything better.

You guys might want to also review the documentation, English is not my first language.

As you can see I wrote tests covering most cases, and the coverage is 100% for the file.

[megawac]

Could this not also be accomplished with find/detect? This looks extremely similar (especially if we consider committing to the proposal in #1248/#591)

[alFReD-NSH]

It doesn't say in the documentation what happens when there's an error in detect. I believe right now it short circuits on error.
Also note that there's no data to iterate on with my use case. There's just a series of functions. That's why it's in the control flow category. It'll be slightly more code for the user to achieve this use case with detect.

[hargasinski]

Related to the discussion in #1248. Should this be callback(!err)? If the task returns an error and a partial result (e.g. {}), the function should probably move onto the next task as opposed to returning.

[alFReD-NSH]

You're right. It should be callback(!err). I'll change it today.

[hargasinski]

I would be in favour of resolving #1248 before moving forward with this PR.

[hargasinski]

Just an fyi, some of the JSDoc tags were duplicated here.

[alFReD-NSH]

@hargasinski I have fixed the issues you mentioned :)

[aearly]

I think this is really cumbersome to expect people to implement with find/some, mainly because those iterate a collection of values, rather than a collection of functions. Here's my stab at it:

function nihTryEach(fns, done) {
  var lastResult;
  var lastError;
  async.some(fns, function (fn, cb) {
    fn(function(err, result) {
      lastErr = err;
      lastResult = result;
      cb(null, !err);      
    });
  }, function (err, anySucceeded) {
    if (!anySucceeded) return done(lastError);
    done(null, lastResult);
  }
}

It's slightly more complicated than @alFReD-NSH 's implementation. I also think the concerns in #1248 wouldn't affect this implementation, we can deal with those separately.

I'd say this is good to merge as-is now. 👍

[aearly]

Released in v2.4.0!