Add support for FORCE_COLOR environment variable to tsc

Suggestion

🔍 Search Terms

FORCE_COLOR

✅ Viability 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, new syntax sugar for JS, etc.)
• This feature would agree with the rest of TypeScript's Design Goals.

⭐ Suggestion

https://github.com/chalk/supports-color/blob/main/index.js

Among the npm/js ecosystem it is common to support overriding color output through an environment variable named FORCE_COLOR. The most commonly used implementation being the 'supports-color' library maintained by the 'chalk' team, linked above. The basic behavior is...

If FORCE_COLOR is "0" or "false" then force plain, uncolored output
If FORCE_COLOR is "1" or "true" then force 16 color ANSI output
If FORCE_COLOR is "2" then force 256 color ANSI output
If FORCE_COLOR is "3" then force full 24-bit RGB output

This ends up being particularly useful for writing tools that act as wrappers around tsc, which might spawn a tsc process and then display its output.

I think the tsc only ever uses 16 color output, which would simplify implementation a little bit.

📃 Motivating Example

The ability to run tsc in a task harness, while still getting colored output, without needing to do any weird argument/configuration injecting.

💻 Use Cases

The particular use case that I'm working on is a CLI tool that can invoke other CLI tools in parallel, such as ESLint, TSC, Prettier, Jest, TypeDoc, etc. The output of each process is piped into a set of buffers until the process exits, and then the buffer is piped out to stdout/stderr as appropriate. You get the speed benefits of running all the tooling in parallel, without needing to have 5+ terminals open to run them all manually, and without the output of each tool getting mixed with the output of others and becoming mangled and hard to read.

[jest]
--- Full color, continuous Jest output ---
[tsc]
--- Full color, continuous tsc output ---

etc.

issue にはリポジトリのファイルもテストも指定されていません。まず tsc のカラー出力処理を見つけ、次に要求された FORCE_COLOR の値をリンク先の supports-color の動作と比較してください。tsc が文書化されたオーバーライドに従い、通常の出力動作を維持できれば完了です。