Suggestion: make hover tooltips more readable by showing the generic parameters names instead of their value (in some cases)..

🔍 Search Terms

tooltip generic parameters
expandable hover
format hover

Related issues:

• https://github.com/microsoft/TypeScript/issues/59029

I searched for both open and close issues, didn't found a duplicate, maybe I didn't use the correct search terms.

✅ Viability Checklist

• 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 isn't a request to add a new utility type: https://github.com/microsoft/TypeScript/wiki/No-New-Utility-Types
• This feature would agree with the rest of our Design Goals: https://github.com/Microsoft/TypeScript/wiki/TypeScript-Design-Goals

⭐ Suggestion

For readability sake, when displaying type info in the hover tooltip, it is better (in some cases) to show the generic parameters' names instead of their value.

The rule could be that when a generic type parameter exceed a certain size, to show its name instead of its value (with the possibility to expand it).

📃 Motivating Example

function foo<T extends Record<string, any>>(o: T) {
    return class X {
        constructor(a: number, b: string) {}
    }
}

const X = foo({
    f1: 34, f2: 34, f3: 34, f4: 34, f5: 34, f6: 34, f7: 34, f8: 34, f9: 34, f10: 34,
});

new X(12, "ok")

Playground Link

When editing new X() arguments, the following tooltip is showing:

X(a: number, b: string): foo<{ f1: number; f2: number; f3: number; f4: number; f5: number; f6: number; f7: number; f8: number; f9: number; f10: number; }>.X

This can quickly become hard to read if the generic parameters are complex. The following would be easier to read (while keeping the ability to expand it*).

X(a: number, b: string): foo<T>.X

_*Well, maybe expansion is not always the solution, and instead of showing the full type definition, to be able to browse the type, e.g. clicking on "T" to show its value (in another hover or by expanding it). Could be more appropriate when we want more precision on one part of the type, not on the whole type.

*Note: TS Playground doesn't seem to have the expandable hover tooltip feature._

💻 Use Cases

1. What do you want to use this for?

Improve hover tooltip readability.

2. What shortcomings exist with current approaches?

Tooltip can be hard to read.

3. What workarounds are you using in the meantime?

Some VSCode extensions, enable to "prettify" hover tooltips to some extends (e.g. MylesMurphy.prettify-ts).

The alternative would be to format the output to improve readability:

X(
        a: number,
        b: string
): foo<
            { f1: number; f2: number; f3: number; f4: number; f5: number; f6: number; f7: number; f8: number; f9: number; f10: number; }
      >.X

リンクされた TypeScript Playground を使って動機となる例を再現し、報告されているホバーツールチップの出力を確認します。リポジトリのファイル、テスト、実装のエントリーポイントのいずれも指定されていないため、まずサイズのしきい値、展開の動作、想定されるジェネリックパラメーターの表示を明確にします。ホバー時の出力がより読みやすくなり、基になる型を調べるための適切な方法も維持されていれば完了です。