[RFC]: Add function type config, and overrides ability for tools.swc

[JSerFeng]

What problem does this feature solve?

Some users need more detailed control of SWC, and there are many many configurations in SWC, currently builder-plugin-swc only exposes some frequently used options, like the react and env fields of SWC configurations.

But some users may need some more config that we do not notice, like for mobx users, they need to set useDefineforClass option, I've never noticed this before, and I cannot guarantee that I can take all the configs into account in the future either, so it's necessary for users to have full control of SWC.

Function type config support

We can use function type config, and let users have full control of SWC. we pass the whole config and some utilities to it, give our users abilities to modify the whole config

Overrides config

Some users wanted that, enable a specific plugin only in file foo, and enable other plugins in file bar. Or if SWC minimizer has bugs in some files, we can disable minimize only in those files. It's similar to babel's overrides

What does the proposed API look like?

We can support function type config, and pass some useful utilities.

{
  tools: {
      swc(swcConfig, { presetReact, presetEnv, mergeConfig }) {
         const config = mergeConfig({
            jsc: { transform: { useDefineForClassFields: true } }
         })

         return config;
      }
  }
}

And overrides like:

Object config:

{
  overrides: [ { include: ['./bug-file.ts'], jsMinify: false }  ]
}

Function config:

{
  tools: {
    swc(config, { addOverride }) {
        # helper utility
        addOverride('./bug-file.ts', { jsMinify: false })
      
        # or modify directly
        config.overrides.push({ include: [/node_modules\/foo/], {  jsc: { transform: { useDefineForClassFields: true } } } })
      }
  }
}

[chenjiahan]

Can we implement this in the framework level?

EdenX framework provides a tools.swc config, we can enhance it and support function type, just like tools.webpack and tools.babel.

[JSerFeng]

Can we implement this in the framework level?

Yeah, that is what I thought, all the examples above, is for tools.swc, both for edenx and modern.js, not direct builder plugin

[chenjiahan]

Do we really need a addOverride util?

It seems we are using different swc configs for different files. If users configure it, it may be difficult to migrate to Rspack in the future.

[JSerFeng]

Do we really need a addOverride util?

It seems we are using different swc configs for different files. If users configure it, it may be difficult to migrate to Rspack in the future.

Overrides is just for framework level, under the hood it will just become different module.rules, like:

rules: [ { test: /foo.js/, loader: 'swc-plugins/loader', options: optionForFoo }, { test: /bar.js/, loader: 'swc-plugins/loader', options: optionForBar } ]

So we don't have to modify bindings

[chenjiahan]

Overrides is just for framework level, under the hood it will just become different module.rules

Get, but we do not provide this feature for Babel, so I'm wondering if we need to provide it for SWC. Is there some real business needs here?

[JSerFeng]

Get, but we do not provide this feature for Babel, so I'm wondering if we need to provide it for SWC. Is there some real business needs here?

It can be an escape when we encounter some tricky SWC transform issues, and only appear in one file and with some configs. For example useDefineForClassFields when using mobx with decorators

[chenjiahan]

Get, it makes sense.