Allow to generate type declaration files with `tsc` when the builder is `swc` or to skip building in `nest start`

[ziyuang]

Is there an existing issue that is already proposing this?

• I have searched the existing issues

Is your feature request related to a problem? Please describe it

It seems when using swc, we cannot generate the *.d.ts files [1,2] needed by, e.g., MikroOrm's TsMorphMetadataProvider [3,4]. One of the workarounds to call tsc -p tsconfig.declaration.json, with

// tsconfig.declaration.json
{
  "extends": "./tsconfig.json",
  "compilerOptions": {
    "emitDeclarationOnly": true,
    "declaration": true,
    "declarationDir": "./dist"
  }
}

after the building step.

However, when using nest start, this will require manually splitting the start command into:

1. Setting "deleteOutDir": false in the compilerOptions of nest-cli.json
2. rm -rf ./dist
3. nest build
4. tsc -p tsconfig.declaration.json
5. nest start

which seems cumbersome.

Describe the solution you'd like

It would be convenient if we could do something like nest --generate-declarations start or nest build && tsc -p tsconfig.declaration.json && nest --skip-builder start (or nest --builder none start). We may add some checks before the this.runBuild line in start.action.ts to achieve this.

Teachability, documentation, adoption, migration strategy

No response

What is the motivation / use case for changing the behavior?

See the first section.