feat: Support for Plugin API

[johnsoncodehk]

Closes #185

Please note that the API interface is not stable, it may change before v1.0.

Usage

• tsconfig.json

{
  "vueCompilerOptions": {
    "plugins": ["./your-plugin"]
  }
}

Example: https://github.com/johnsoncodehk/volar-starter/blob/master/vue-i18n.js
Built-in plugins: https://github.com/johnsoncodehk/volar/tree/master/packages/vue-language-core/src/plugins

[phil294]

Hi, thanks for your work on this! This should make adding e.g. a custom HTML parser a breeze. However, am I understanding the plugin syntax correctly, in that it is not yet possible to integrate an external LSP for scripts (#533)? (Or at least not without significant effort) So that go-tos, autocomplete etc. all can work with JS preprocessor languages like CoffeeScript or Elm, when there exists a LSP server implementation. It would be great to just plug them in somehow.

[johnsoncodehk]

@phil294 You can convert CoffeeScript code to TypeScript code with mapping in resolveEmbeddedFile API, it can provide the same level language capabilities as TypeScript script blocks in theory. But currently implement cannot reuse https://github.com/johnsoncodehk/volar/blob/master/packages/vue-language-core/src/plugins/vue-tsx.ts code-gen logic with JS preprocessor, so yes this way not without significant effort.

You can open a feature request (and best to attach sample repro, so I can see what I actually need to solve), I need to find a suitable implementation.