Tsup doesn't accurately collect tsconfig.json preferences

After some testing, it looks like tsup doesn’t resolve tsconfig extensions. For example, if my tsconfig was:

{
	"extends": "../tsconfig.base.json",
	"compilerOptions": {
		"baseUrl": "."
	}
}

And ../tsconfig.base.json was:

{
	"compilerOptions": {
		"emitDecoratorMetadata": true
		...
	}
}

Tsup wouldn’t detect any of the extended options, such as emitDecoratorMetadata. This seems to be because you only read the file through fs.readFileSync and use the results directly. However, I believe you need to use typescript’s compiler API to get the full contents. Something like this:

const parsedTsConfig = typescript.parseJsonConfigFileContent(tsconfig, typescript.sys, outDir);

You can find a good example of that here, and I could also probably make PR if needed.

[egoist]

This should be fixed in 5.11.12, please give it a try

btw I made a package for this: https://github.com/egoist/load-tsconfig (even more light-weight than tsconfig-loader)

[Lioness100]

Great, thank you so much! Can I also make a PR that adds the option to force tsup to use esbuild over swc, even if the emitDecoratorMetadata is enabled somewhere? (Nevermind, I just won’t install @swc/core)