Proposal: Inlay Hints with minimal parameters count

Suggestion

🔍 Search Terms

Inlay Hints, LSP, VS Code integration

✅ 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.

📃 Motivating Example

From https://github.com/microsoft/vscode/issues/147875

With javascript.inlayHints.parameterNames.enabled: 'all', we got

parseInt(/* str: */ '123', /* radix: */ 8)

While in many cases, we only use one parameter when calling a function, for example

parseInt(/* str: */ '123')

console.log(/* message: */ foo)

// Vue's Composition API
const state = ref(/* value: */ 1)

array
  .filter(/* predicate: */ Boolean)
  .map(/* callbackFn: */ i => i.value)

In those cases, the contexts are less ambitious and the inlay hints become a bit redundant and even verbose.

⭐ Suggestion

Thus I am proposing to introduce a new setting to configure the minimal parameters count required for the inlay hints to enable in each function call.

Able to have this setting fields in VS Code:

"typescript.inlayHints.parameterNames.minCount": 2 /* default: 0 */

To hide the inlay hints when calling functions with a single argument.

Thus we could expose an additional preference entry for

interface InlayHintsOptions extends UserPreferences {
  includeInlayParameterNameHintsMinCount: 2
}

I had the implementation ready at https://github.com/antfu/TypeScript/commit/395477592183cf555ab5cea6b0eaa041ae2a757b . Could send a PR if the team agrees on this change.

💻 Use Cases

To provide a cleaner code reading experience for common functions while having the ability to have inlay hints for complex functions.

[andrewbranch]

you just might not always remember which arg goes where

I have no idea what you’re talking about

[mjbvz]

I like #48899 a lot more than using parameter count as a proxy of whether inlay hints may be helpful. I’ve seen plenty of functions that take a single argument whose purpose is not clear until you look up the argument’s name