Fix bug: keep comments unless --removeComments

[staltz]

Fixes #2546.

This is a straightforward fix for bug #2546. Keeps most or all TS comments
in the output, unless the option --removeComments is enabled.

(CLA signed, DocuSign Envelope ID: 2F26CC42-D7EE-48C6-B680-A6C0E3F7E58F)

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[DanielRosenwasser]

This output is undesirable because it's extremely misleading. There's a reason we don't emit every comment, and this is the typical example of why.

[staltz]

But issue #2546 is precisely about keeping these comments. And it said PRs are welcomed. Can we define what are precisely the conditions to hide or show comments? Should we keep all comments of the type /** */ or also // (the original reporter in #2546 wanted the latter too)?

[RyanCavanaugh]

Can we define what are precisely the conditions to hide or show comments?

Honestly, that's the hard part (if we had a good rule, we would have done it already). Clearly leading comments for type declarations shouldn't be present in the emit as they look like misleading nonsense, but comments between an opening brace of a statement block and another expression statement should be present.

Figuring out where it makes sense to emit the comments and where it doesn't is the hard part. Simply emitting every comment isn't the right fix.

[DanielRosenwasser]

Thanks for sending this out @staltz, but since this isn't the correct approach, I'm going to close this PR. Feel free to follow up with a new one though.

[staltz]

I'm not going to submit a new PR until there is a clear notion of what #2546 actually means and what is the acceptance criteria. It serves us (RxJS project) a real purpose: being able to keep JSDoc-style comments (/** */) for things like interfaces et al.

[benlesh]

Is it really a transpiler's business to decide which comments have value? Transpilers can't read. Seems strange. IMO, this should be "all in" or "all out" barring comments that take some standard convention that signifies something you don't want removed to contain, say, a license or copyright. There is prior art for that.

[grlscz]

May we have a flag to keep ALL comments, if we really want it?