Computed object keys produce very odd output

Hi, I’m seeing some strange-looking output when using square brackets to quote object keys.

const a = { ['foo']: 1};
const b = { ['bar']: 2};
console.log(a, b);

becomes:

var a={},b=(a.foo=1,a),c={},d=(c.bar=2,c);console.log(b,d);

Appspot link here. It gets worse: more intermediary objects are created as you add more keys.

I’d expect the result to be closer to the setup without [], i.e.:

console.log({foo:1},{bar:2});

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Further context: this came about as we’re looking to use Prettier to format code in our project, but can’t easily do so as it unquotes keys that don’t strictly need to be quoted. This breaks instances where we need quoted keys not to be mangled by Closure Compiler.

One of the workaround people are using is { ['foo']: bar } syntax, which Prettier won’t unquote, but that produces bad output when fed into CC.

[lauraharker]

Sent out a fix for internal review. I’d estimate it will be in the May release.

[lauraharker]

Sorry I haven’t updated this in a while. Thanks for the numbers. After some internal review, we do still want to fix this, but in a way slightly more complicated than my initial proposal to deal with the restriction on duplicate object literal keys in ES5 strict mode.

Filed Google internal bug b/120031769.