Allow "Compiler Plugins"

From wiki:

TypeScript Language Service Plugins (“plugins”) are for changing the editing experience only

TypeScript plugins are very limited. Plugins should be able to:

• Apply Transformers
• Provide type definitions
• Override module resolver (LanguageServiceHost#resolveModuleNames)
• Emit code beside TypeScript standard output

[mohsen1]

I’m not familiar with TypeScript well enough to write a proposal. Instead I can list a few plugins that can be useful and exist in the wild in other forms (Webpack plugin, Babel transforms) to make a case for having such extensibility:

Custom module resolution

• Typed CSS Modules
• JSON-loader
• YAML-loader
• Loading any type of serializable file with types

Code transformers

• babel-plugin-jest-hoist
  • issue
• Minifiers
• Removing debug code

Emitting other code

• A Swagger code generator embedded in TypeScript plugin
  • gist about this idea
• Functionality similar to Webpack: emitting image and other asset files

Providing types

• Typed GraphQL query responses
  • This applies to pretty much any database query language. Result of a query can be typed based on query

There are so many other use-cases for compiler plugins that I’m not aware of but I’m sure compiler plugins will make TypeScript ecosystem thrive.

[glen-84]

@DanielRosenwasser,

The TypeScript 3.8 Iteration Plan included “Plugin Investigation” under the Expected Work Items – was any progress made in that regard?

Will this issue be considered for the next roadmap (July - December 2020)?