fix transpileOnly usage with fork-ts-checker

[desmap]

docs are wrong: transpileOnly: true paired with fork-ts-checker together turns off type-checking entirely; just fork-ts-checker is sufficient

[johnnyreilly]

I don't understand your edit here I'm afraid; setting transpileOnly: true is a ts-loader option only and should have no effect upon the behaviour of the fork-ts-checker-webpack-plugin.

[desmap]

hey @johnnyreilly,

should have no effect upon the behaviour of the fork-ts-checker-webpack-plugin.

this is also what I don't get and in my prior apps I assumed exactly what you write.

But when I was benchmarking I found that type checking was turned off if you have both transpileOnly: true ("tO") in the ts-loader options and fork-ts-checker ("ftsc") as plugin enabled. I tested this multiple times with deliberate type errors. Also look at my benchmarks at the two different versions: The tO + ftsc was as fast as the pure tO version and faster than the pure ftsc version. Test it yourself.

[desmap]

just tested again and added a type error to one of the 1,000 functions:

(param: string) => {
  const extraError: number = param
  console.log(extraError)
}

CASE A transpileOnly: true in ts-loader options + fork-ts-checker enabled:

Entrypoint main = runtime~main.js main.js
[./client/index.tsx] 89.5 KiB {main} [built]
    + 47 hidden modules
ℹ ｢wdm｣: Compiled successfully.
No issues found.

CASE B just fork-ts-checker enabled:

Entrypoint main = runtime~main.js main.js
[./client/index.tsx] 89.5 KiB {main} [built] [1 error]
    + 47 hidden modules

ERROR in [...]/client/index.tsx
./client/index.tsx
[tsl] ERROR in [...]/client/index.tsx(4003,11)
      TS2322: Type 'string' is not assignable to type 'number'.
ℹ ｢wdm｣: Failed to compile.

CC @appzuka

Edit: i have projectReference: true and fwiw, I added the type error to a non-reference/main file.
Edit2: i just added the type error instead to a reference file and type errors are emitted with CASE A and CASE B

[johnnyreilly]

Edit: i have projectReference: true

This seems significant. Do you want to repeat your test in a non-project references context. I suspect that's what's causing your issue.

[desmap]

I did already in Edit2 and in this probably related thread: #1158 (comment)

[desmap]

Ok then this pull is obsolete and it's something different, closing