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Rethink enumerability hack for symbols #7

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medikoo opened this issue Mar 24, 2015 · 4 comments
Open

Rethink enumerability hack for symbols #7

medikoo opened this issue Mar 24, 2015 · 4 comments
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@medikoo
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@medikoo
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medikoo commented Mar 24, 2015

Currently naturally set symbol properties (via e.g. x[symbol] = 'foo') are defined under the hood as not enumerable, so they're hidden from Object.keys and for in iterations.

This however has side effect of symbols not being copied as expected via Object.assign and incorrect value being returned for obj.propertyIsEnumerable(symbol).

Fix would be, to make them naturally enumerable (resign from Object.prototype hack), but update Object.keys shim within es5-ext project so it will filter eventual symbols created by polyfill. Additionally for .. in counterpart can be provided as well.
@medikoo medikoo self-assigned this Mar 24, 2015
@medikoo medikoo added this to the v2 milestone Mar 24, 2015
@medikoo medikoo changed the title Rethink enumerability hack of symbols Rethink enumerability hack for symbols Mar 24, 2015
@WebReflection
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FYI I've solved this in https://github.com/WebReflection/get-own-property-symbols

@WebReflection
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early comment, sorry.

You cannot make them enumerable because for/in will show them. symbols in ES5 make sense only if assigned as non enumerable, but other methods that deal with descriptors should be aware of the poly.

I've patched propertyIsEnumerable together with defineProperty and defineProperties and now my polyfill works well with Object.assign native or polyfilled.

You can still set non enumerable Symbols when you use defineProperty/ies

@medikoo
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medikoo commented Apr 21, 2015

@WebReflection thanks for comment.

Yes as for/in can't be patched, the way you propose, is the only way to get it right

@WebReflection
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forgot to mention that I obviously had to patch Object.getOwnPropertyDescriptor which will return true by default, unless the Symbol hasn't been assigned via defineProperty/ies as non enumerable.

It's a mess but it works :D

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