Typescript: Backward compat issue with non enumerable properties

[deltakosh]

we (babylon.js team) are using a lot of properties and we need to enumerate properties for quite a few scenario (cloning, serialization, etc..)

Can we get a flag in the compiler to restore the previous scenario? This is a big breaking change for us?

Thanks a ton!

TypeScript Version: 3.9.5

Search Terms: Enumerable

Code no code related. We just need a way to preserve back compat while we migrate our code to a different pattern

Expected behavior: An option in the compiler to keep the properties enumerable

Actual behavior: Properties are not enumerable

[RyanCavanaugh]

Which properties? Class properties? Are they initialized? What are your compiler settings?

[AviVahl]

He's probably referring to https://github.com/microsoft/TypeScript/pull/32264 which was documented in the release notes as a breaking change.

@deltakosh consider using Object.getOwnPropertyNames when you need to enumerate these properties. see: https://stackoverflow.com/questions/8024149/is-it-possible-to-get-the-non-enumerable-inherited-property-names-of-an-object

[RyanCavanaugh]

If we add a flag we'll have to maintain it forever, so no. You can stay on 3.8 until you're ready to upgrade

[deltakosh]

well it was a fast discussion :)... We cannot use for in anymore (only 617 entries in babylon.js, should be easy)

[AviVahl]

All those for in usages would break once you've dropped es5: https://jsbin.com/wizededujo/edit?js,console

The previous inconsistency in behaviour between es5 and es2015 targets was way more problematic, and I personally appreciate this change.

[deltakosh]

Oh but don’t get me wrong I do appreciate it but I could also have appreciated a grace period. If we want to stick with latest versions, we have no option but do a large change in our codebase

[RyanCavanaugh]

It's not like you couldn't have removed your code's dependence on a spec incompliance any time between now and whenever you wrote it. If we give you a flag now, then take it away later because it's a maintenance burden, all that does is change when in time you'd be unable to immediately upgrade.

[deltakosh]

Well first I was not aware of the incompliance until today. Furthermore even if I knew, I would have taken for granted that TS was setting the enumerable to true for me
More generally speaking, it could be useful to log a warning on the console to announce some incoming breaking changes of that magnitude

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