Control TSC's noEmit or emitDeclarationOnly when using composite projects

[pleerock]

create-react-app doesn't work in composite typescript projects, because for composite projects emitDeclarationOnly must be used instead of noEmit (when using noEmit: true and composite: true typescript compiler throws an error). I suggest to add a check - if typescript project is composite-based, use emitDeclarationOnly flag instead of noEmit.

See microsoft/TypeScript#36917 for more information.

[CodingDive]

Not entirely sure if this is related but I'm using lerna with TypeScript projects. In the root directory, I watch all packages with the --incremental flag which requires noEmit to be false. When I change noEmit: true, CRA adds it back.
Therefore, I needed to remove the --incremental flag which might negatively impact the performance of large TypeScript projects.

[pleerock]

@CodingDive it is related.

[slikts]

Options for incremental builds can look like this:

    "incremental": true,
    "emitDeclarationOnly": true,
    "outDir": ".cache/tsbuild",
    "skipLibCheck": true

Adding support for the incremental option was previously proposed in #6785, but was closed due to the webpack plugin already using incremental builds, but I think that misses the point; it's also useful to check types with tsc without building, since it's faster and allows to type check files that aren't open in an editor.

[youbek]

Same here, I want to add composite to true, which cannot go with noEmit. so, I am trying to remove the noEmit, but CRA adding it back. Any solutions?

[CodingDive]

@slikts that seems like a good config for incremental builds indeed. Unfortunately, as reported by @plreerock even emitDeclarationOnly won't work when CRA always sets noEmit back to true.

For anyone running into the same error: error TS5053: Option 'emitDeclarationOnly' cannot be specified with option 'noEmit'.

[MichaelFroeschen]

This is still a thing... I'm kinda getting annoyed by the fact, that some options are forced in such a way, without any explanation...

[mikehardy]

@entropitor appears to have nailed this one with his PR. I checked it carefully and it fixes things for me 100%

I attached a patch-package file over on the PR for anyone to use while waiting for the PR to settle: #10921 (comment)