WebIDL parameter Promise type not converted when in a nested type, e.g. ClipboardItemData

[wffurr]

WebIDL has an implicit conversion mechanism for an ECMAScript value V into an IDL Promise<T> type. This means that any function defined in WebIDL that accepts a Promise<T> implicitly accepts T|Promise<T>.

However, the generated TypeScript typings for a WebIDL function that accepts a Promise<T> argument only have the type Promise<T>, and not the non-Promise T type. The generated typings should have T|Promise<T>.

e.g. in https://w3c.github.io/clipboard-apis/#clipboard-interface, the ClipboardItem constructor takesClipboardItemData as the values in the items record. The generated typings for that type should be string|Blobl|Promise<string|Blob> but instead it's just Promise<string|Blob>.

See wffurr@9c8bc4b for an example.

[wffurr]

I see there's some code to handle this already:

TypeScript-DOM-lib-generator/src/emitter.ts

Line 749 in a75338e

p = { name: p.name, type: [p.subtype!, p] };

It works great for the Payment Request API:

TypeScript-DOM-lib-generator/baselines/dom.generated.d.ts

Line 11313 in a75338e

show(detailsPromise: PaymentDetailsUpdate | Promise<PaymentDetailsUpdate>): Promise<PaymentResponse>;

But not for ClipboardItemData because it's in the value position of a record type that is itself a parameter to a function. The recursion in paramsToString would have to propagate the knowledge that a parameter is being converted and conditionally modify any Promise types that are passed in to the browser but not ones come back from the browser, e.g. return types of callback arguments but not parameter types of callback arguments.

[saschanaz]

#1102

@github-actions close

[github-actions]

Closing because @saschanaz is one of the code-owners of this repository.