Codefix: convert `Type[]` to `readonly Type[]`

Search Terms

codefix readonlyarray readonly array immutable

Suggestion

It'd be nice to have a codefix for converting non-readonly arrays to readonly.

Use Cases

When converting/refactoring code to be more immutable/readonly-friendly, it's a bit of a pain to manually add these annotations.

Examples

Given this:

function takesArrays(items: /*| |*/string[], moreItems: /*| |*/string[]) { /* ... */ }

...having a codefix to make one or all parameters readonly would be useful:

function takesArrays(items: readonly string[], moreItems: readonly 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.

issue の TypeScript の例と、関連する型注釈用の既存の codefix インフラストラクチャから始めます。codefix のエントリポイントとそのテストを特定し、該当する 1 つまたはすべてのパラメーターの変換を実装して、結果の型が readonly 配列構文を使用していることを確認します。