module: remove --experimental-transform-types

[marco-ippolito]

This PR removes the --experimental-transform-types flag and all related code, tests, and documentation.
It also changes the following user facing APIs:

• stripTypeScriptTypes now only accepts the code to transform, and not the options object.
  It also does not add a sourceURL comment at the end of the transformed code.
• process.features.typescript now only returns a boolean.
  Technically the stripTypeScriptTypes could have landed as a separate commit but I believe since it's a semver major commit it makes no difference.

Refs: nodejs/typescript#51

[nodejs-github-bot]

Review requested:

• @nodejs/config
• @nodejs/loaders
• @nodejs/performance
• @nodejs/startup
• @nodejs/typescript

[GeoffreyBooth]

process.features.typescript now only returns a boolean

I think we should add process.features.stripTypes that returns a boolean. This should be a separate PR so that it can be backported.

Then the question becomes what to do with process.features.typescript. I think having a feature called typescript only makes sense if the overall feature has various modes, like currently it's either off (false), strip or transform. But we might someday add other TypeScript-related features like type checking, or tsconfig.json support, or support for various features within tsconfig.json; and these might be individual features to be toggled on or off (like maybe a user enables tsconfig.json paths support but not type checking) and so a single string value for an overall mode doesn't make sense. We could make process.features.typescript a Record<string, boolean> so that there's something like process.features.typescript.strip === true and other features add onto there, or treat each new TypeScript-related feature as a top-level key on process.features.

For the purposes of this PR, perhaps the simplest thing to do would be to just keep process.features.typescript as it is but remove transform as a possible return type. Then a redesign of process.features.typescript can happen in a dedicated PR.

[marco-ippolito]

User can run --no-strip-types so typescript might not be enabled

[aduh95]

• process.features.typescript now only returns a boolean.

I wouldn't do that:

• it's perfectly workable as is, as a string
• if we end up re-introducing --transform-type or another type of typescript handling, it will put us in an awkard position.

Why risk it?

[styfle]

if we end up re-introducing --transform-type or another type of typescript handling, it will put us in an awkard position.

If we think thats a possibility in the future, then we should keep process.features.typescript as a string and also keep the options object in stripTypeScriptTypes() so we can allow strip but throw and error for other modes.

TLDR - keep this semver-major change as breaking only for those using transform but anyone using strip should not have a breaking change. Does that make sense?

[codecov]

Codecov Report

❌ Patch coverage is 75.00000% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 89.67%. Comparing base (e687680) to head (c62af40).
⚠️ Report is 5 commits behind head on main.

Files with missing lines	Patch %	Lines
lib/internal/modules/typescript.js	83.33%	1 Missing ⚠️
src/compile_cache.cc	0.00%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #61803      +/-   ##
==========================================
- Coverage   89.73%   89.67%   -0.06%     
==========================================
  Files         675      675              
  Lines      204676   204668       -8     
  Branches    39330    39281      -49     
==========================================
- Hits       183660   183536     -124     
- Misses      13293    13419     +126     
+ Partials     7723     7713      -10     

Files with missing lines	Coverage Δ
lib/internal/bootstrap/node.js	98.95% <100.00%> (-0.02%)	⬇️
src/compile_cache.h	100.00% <ø> (ø)
src/node_options.cc	76.20% <ø> (-0.08%)	⬇️
lib/internal/modules/typescript.js	91.39% <83.33%> (-6.09%)	⬇️
src/compile_cache.cc	79.15% <0.00%> (-1.63%)	⬇️

... and 50 files with indirect coverage changes

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[GeoffreyBooth]

This PR's goal is to remove transform-types. So in this PR, I think just remove the transform response from process.features.typescript. Any other rethinking or redesign of that property can come in a follow-up PR.