fix transform-typescript logic to remove definite fields

[akphi]

Q	A
Fixed Issues?	Fixes #12146
Patch: Bug Fix?	Yes
Major: Breaking Change?
Minor: New Feature?
Tests Added + Pass?	Yes
Documentation PR Link
Any Dependency Changes?
License	MIT

I made sure to separate the handling for 2 cases: fields defined with the keyword declare and fields defined using the definite assignment operator.

For the latter, when the flag allowDeclareFields is true (can be treated equivalent to Typescript useDefineForClassFields = true) we will not remove the field.

Also, since I separate the handling, I adjust the error message thrown by each case slightly when the fields in these 2 cases are given values.

Also, I added a test for allowDeclareFields = false to ensure old behavior works fine

@nicolo-ribaudo What you said about babel's allowDeclareFields is similar to Typescript's useDefineForClassFields is interesting. Should we update the doc for transform-typescript here?

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Build successful! You can test your changes in the REPL here: https://babeljs.io/repl/build/29481/

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[akphi]

@nicolo-ribaudo please, could you take a look when you have some time?

[nicolo-ribaudo]

Thanks!

[nicolo-ribaudo]

Should we update the doc for transform-typescript here?

Do you want to open a PR to the babel/website repo to add it to this list? https://babeljs.io/docs/en/babel-plugin-transform-typescript#typescript-compiler-options

[akphi]

@existentialism @JLHwung @nicolo-ribaudo I'm new to contributing, is there anything else I need to do to get this merged?

And afterward, do you have a timeline in mind when we can release this change?

[nicolo-ribaudo]

We have a 2-:heavy_check_mark: policy. After another approval, we can merge this PR and release it in the first next version (7.11.8 or 7.12.0).

[existentialism]

@akphi thanks!

[akphi]

@nicolo-ribaudo @existentialism Thanks! I was about the make the changes you suggest 😀 Not too familiar with the release cycle of babel myself, when do you have an estimate for when will this happen?

[existentialism]

Soon :)