block-scoped-var fails on mutual recursion

[RReverser]

Simplified my case to the following code:

function a(n) {
    return n > 0 ? b(n - 1) : "a";
}

function b(n) {
    return n > 0 ? a(n - 1) : "b";
}

And simplified eslintrc that allows to reproduce the issue:

{
  "ecmaFeatures": {
    "blockBindings": true,
    "modules": true
  },
  "rules": {
    "no-use-before-define": 2,
    "block-scoped-var": 2
  }
}

Without blockBindings enabled, only no-use-before-define fails.
Turning modules on/off doesn't affect the result, only adds use strict-related check in this case.

[michaelficarra]

@RReverser no-use-before-define doesn't allow the reference to appear anywhere before the definition in the program text. The more sane configuration, in my opinion, is the nofunc option, and it should fix your problem.

[RReverser]

@michaelficarra Doesn't help for classes though (which was my original case).

I'd just wish the rule would be somewhat smarter and wouldn't warn when definition outside of the function/class boundary is referenced.

Also - what about block-scoped-var?

[michaelficarra]

There's a proposal to fix that: #2750

What's the problem you're having with block-scoped-var?

[RReverser]

See title - it also fails with given example & config.

[RReverser]

There's a proposal to fix that: #2750

Haha, just in time :)

[nzakas]

@RReverser can you provide the actual ESLint output as well as what you'd expect the output to be?

[RReverser]

Sure, here it is:

x.js
  2:19  error  b was used before it was defined     no-use-before-define
  2:19  error  "b" used outside of binding context  block-scoped-var

✖ 2 problems (2 errors, 0 warnings)

I expected not to see any of these errors.

[nzakas]

It looks like nofunc solves your problem here, and #2750 would take care of the rest of your concerns there. So let's focus this issue on block-scoped-var.

block-scoped-var probably would need to be rewritten in order to properly support hoisting, as this looks like a bug.

[RReverser]

Thanks!

[mysticatea]

I will try to fix bugs around block-scoped-var rule.