Async LanguageServiceHost

Search Terms

language, service, host, async, api

Suggestion

It'd super awesome if Language Service would accept a LanguageServiceHost with async API

Use Cases

Using LanguageService in environments where readFileSync is not available like browsers (using browserfs package or fs provided by WebSockets)

I'm working on an app like CodeSandbox but a bit more sophisticated.

Examples

class Host implements ts.LanguageServiceHost {
  async getScriptSnapshot(filename: string): Promise<ts.IScriptSnapshot> { }
  async readFile(filename: string): Promise<string> {}
}

Checklist

My suggestion meets these guidelines:

• This wouldn't be a breaking change in existing TypeScript/JavaScript code
• This wouldn't change the runtime behavior of existing JavaScript code
• This could be implemented without emitting different JS based on the types of the expressions
• This isn't a runtime feature (e.g. library functionality, non-ECMAScript syntax with JavaScript output, etc.)
• This feature would agree with the rest of TypeScript's Design Goals.

Start with the LanguageServiceHost and LanguageService APIs described in the issue, comparing their current synchronous assumptions with the async getScriptSnapshot and readFile examples. Determine the required API design for browser environments where readFileSync is unavailable; done means an async host can be used without breaking existing TypeScript or JavaScript code.