Nested loop at the end of function fail on Don't make functions within a loop

[jakubzitny]

This coffee code fails on ?:?: Don't make functions within a loop.

letts = [ 'a', 'b', 'c' ]
nums = [1, 2, 3]

fun = ->
  for lett of letts
    for num of nums
      console.log(lett, num)

fun()

The fact that the for loop is last statement means, coffee wants to return its value. If the loop has another loop in it, there is anonymoous function inside the loop that "collets" the values to return. Transpiled js looks like this:

(function() {
  var fun, letts, nums;
  letts = ['a', 'b', 'c'];
  nums = [1, 2, 3];

  fun = function() {
    var lett, num, results;
    results = [];
    for (lett in letts) {
      results.push((function() {
        var results1;
        results1 = [];
        for (num in nums) {
          results1.push(console.log(lett, num));
        }
        return results1;
      })());
    }
    return results;
  };

  fun();
}).call(this);

Do you guys think, it would make sense to add "Don't make functions within a loop." to errorsToSkip in hint.coffee?

[cueedee]

While I agree that your particular example seems to make a case in favour of adding this warning to the ignore list, doing so would also cause very legitimate reports to start slipping under the radar; such as in:

funcs = (( ( j ) -> i + j ) for i in [0..10] )

I feel that it is rather the responsibility of jshint itself to intelligently make the distinction between legitimate uses such as in your example and the real problematic cases such as the one above.

[cueedee]

I would like to revoke my previous assertion.

Little did I realise the pervasiveness of this warning until I found that my generator had been confidingly inserting jshint's relaxing loopfunc option into its generated grunt-coffee-jshint config.

Btw, this warning currently comes in the form of "Functions declared within loops referencing an outer scoped variable may lead to confusing semantics.".

So, instead of adding this warning to the errorsToSkip list, which basically is just an escape-hatch for suppressing warnings for which no relaxing options exist, I would rather include loopfunc into the list of jshint's relaxing options that coffee-jshint turns on by default.