RFC-001: loader plugin api design

[hardfist]

We list some problems of different model about loader plugin here #315,
we propose a new loader plugin api.
The Loader Plugin API are split into three parts

• Loader Filter API: decide which loader apply to which module
• Loader API: decide How to transform the Module
• Internal Loader implementation:

Loader Filter API

{
  transformers: [
    {
        include: [path.resolve(__dirname, './src')],
        exclude: [path.resolve(__dirname), './node_modules'],
        resourceQuery: '?loader=svg',
        schmea: 'data' | 'http', // 'http://xxxx', or 'data:javascript,xxx',
        test: /\.svg/, // an rust regex
        assert: { type: 'css' }, // import assertion
       use: [require('svg-loader')(svgOptions), 'jsx'], // if we pass an function it's a user implemented loader，if we pass string it is internal loader
    },
    {
        include: [path.resolve(__dirname, './src')],
        exclude: [path.resolve(__dirname), './node_modules'],
        resourceQuery: '?vue&lang=script',
        schmea: 'vue', // 'vue://xxxx', or 'data:javascript,xxx',
        test: /\.vue/, // an rust regex
        assert: { type: 'vue' }, // import assertion
      use: [require('vue-loader')(svgOptions), '...'], // ... means default loader
    },
  ];
}

For Most of case, test is enough

[
 {
   test: /\.svg/,
   use: [require('svgr)(svgOptions), 'babel']
 },
{
  test: /\.vue/,
  use: [require('vue-loader')(vueOptions),'...'] // means default loader
}
]

Internal Plugin

Loader API

sharing ast

we should consider combine transform and transform_ast into one transform api, and support pass ast from transform to rspack for performance reason.
There are two kinds of ast sharing

• share ast between plugin and bundler
• share ast between plugin

change module type

There are two ways to change module type, parcel way setType(otherType) or webpack way set virtualResource

provide clean url

we should provide clean(unpolluted) url for plugin author like webpack, so provide resource, resourcePath, resourceQuery to plugin author

virtual module

using data url to handle virtual module other than virtual id or query

cache

Todo

sourcemap

Todo

Internal Loader implementation

There is one problem in current implementation, we put our filter logic in the transform implementation, which not works well for filter API. so we need to split the filter logic out of transform implementation.