Incompatible code generated with 1.12.6 using function call followed by if statement.

[jo-soft]

Until version 1.12.5 the code foo bar if baz transpiled to if(baz){foo(bar)}
since 1.12.6 this code transpiles to foo(baz ? bar: void 0) which breaks old code.

But when i use mood = greatlyImproved if singing (from docs) it compiles to if (singing) {mood = greatlyImproved;}
Is this indented? Maybe by 'Bugfixes for incorrect code generated by the ? operator within a termary if statement`? I cant find any Bug report for that.

bg,
Johannes

[GeoffreyBooth]

Are you sure?

[connec]

Perhaps you somehow triggered it being parsed as foo(bar if baz)? It would help if you could paste a full example that's reproducible in Try CoffeeScript (or a link).

[jo-soft]

bigger example of code failing in 1.12.6 bug working in 1.12.5 and lower:

test:
  bam: () ->
    fn bar: {
      foo: 123
    } if not condition

results in 1.12.6 (example generated by: http://coffeescript.org/#try)

({
  test: {
    bam: function() {
      return fn({
        bar: !condition ? {
          foo: 123
        } : void 0
      });
    }
  }
});

results in 1.12.5. (example generated by js2.coffee:

({
  test: {
    bam: function() {
      if (!condition) {
        return fn({
          bar: {
            foo: 123
          }
        });
      }
    }
  }
});

both examples can also locally be reproduced by transpiling locally

[vendethiel]

Paging @helixbass since it might be from #4554 (?).

[helixbass]

@vendethiel not a bad guess but #4554 was only merged into 2

[GeoffreyBooth]

It’s from #4532, allowing implicit braces after a return or export default. Basically, in this code:

test:
  bam: () ->
    fn bar: {
      foo: 123
    } if not condition

it’s ambiguous what the if block should be applied to. “Trailing if“ is only meant for a one-line expression; if anything, we should be throwing an error here. How far back is this if supposed to look to determine whether something should be output? Just { foo: 123 }? Or { bar: { foo: 123 } }? Or fn { bar: { foo: 123 } } or return fn { bar: { foo: 123 } }?

If you insist on a trailing if, make it explicit:

test:
  bam: () ->
    (fn bar: {
      foo: 123
    }) if not condition

I don’t think there’s a bug here. Yes the output changed, but it’s as a result of fixing another bug regarding implicit braces and return. Basically the output here was relying on that bug to create the desired effect.

[GeoffreyBooth]

Actually it's probably due to #4534. But my point still stands.

[vendethiel]

I don't think we should be changing such semantics on 1.x.

[GeoffreyBooth]

Yeah we shouldn’t have merged #4534 into master (assuming that is, in fact, the cause of this). My argument is less valid against that PR than it is against fixing braces after return, because braces after return is more clearly a bug whereas #4534 adjusts behavior to the way it “should” be.

So I guess the question is what to do about it. We’re keeping #4534 on 2, so it seems odd to revert it on master just to keep it in 2. I was hoping to avoid any more 1.x releases.