Tsup doesn't accurately collect tsconfig.json preferences

[Lioness100]

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.

[Lioness100]

My tsconfig:

{
    "extends": "../tsconfig.base.json",
    "compilerOptions": {
        "outDir": "../dist",
        "rootDir": ".",
        "baseUrl": ".",
        "noEmit": true,
        "paths": {
            "#root/*": ["*"],
            "#lib/*": ["lib/*"],
            "#types/*": ["lib/types/*"],
            "#structures/*": ["lib/structures/*"],
            "#utils/*": ["lib/utils/*"],
            "#database/*": ["lib/database/*"]
        }
    },
    "include": ["."]
}

The extended tsconfig has emitDecoratorMetadata

Logs:

[Lioness100]

Furthermore, if there isn't one already, might I suggest an option to manually disable the swc plugin? This would be useful if:

• The option was included in an external tsconfig you're extending, but you're not actively making use of it
• You'd like to create your own implementation of the plugin, either not using swc, or being selective with the files that get transformed with it (maybe only an entities directory if using typeorm, or creating a regex to search for decorators)

[Lioness100]

Should I just submit a PR to the package that reads the tsconfig?

[egoist]

I'd like to use a library that doesn't use the typescript compiler to load tsconfig.json, since tsup should work without typescript

Maybe add an option: loadTsconfigWithCompiler: true (or some other name) before this is implemented.

[Lioness100]

What if, in this library, once and if the raw tsconfig data is collected, the code checks if typescript is installed, uses it to expand the tsconfig if it is, and just keeps the original otherwise?

Edit: loadTsconfigWithCompiler would work fine as well

[cenk1cenk2]

Maybe this one would fit the bill in the sense of not using Typescript.

https://www.npmjs.com/package/tsconfig-loader

[Lioness100]

Oooh that looks perfect!

[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)