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Middleware type definitions don’t match actual API #2360

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Jaid opened this issue Sep 16, 2023 · 1 comment
Open

Middleware type definitions don’t match actual API #2360

Jaid opened this issue Sep 16, 2023 · 1 comment
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DefinitelyTyped typescript

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@Jaid
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Jaid commented Sep 16, 2023 •
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It’s currently not that easy to write middlewares in TypeScript, because the actual API and exported types seem to be out of sync.

This is a legitimate Yargs middleware:

type MiddlewareFunction = (args: ArgumentsCamelCase, yargs: YargsInstance) => Record<string, unknown>

Which can be verified by looking directly at the API code.

yargs/lib/middleware.ts

Lines 111 to 114 in e517318

const result = middleware(acc, yargs);
return isPromise(result)
? result.then(middlewareObj => Object.assign(acc, middlewareObj))
: Object.assign(acc, result);

However, this is the corresponding type definition I am consuming:

https://github.com/DefinitelyTyped/DefinitelyTyped/blob/3a6d407361cc6025d136ae5eb3c3e3e24ada5009/types/yargs/v16/index.d.ts#L838

The problems with that:

  • The second parameter of MiddlewareFunction is not documented.
  • Type YargsInstance doesn’t seem to be accessible.
  • The callback return type is void, but the API user can actually decide between modifying the original args (args.foo = 'bar'; return) and letting Yargs do the merging (const changes = {}; changes.foo = 'bar'; return changes).
@shadowspawn
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The types available for client use are from DefinitelyTyped, and maintained separately. You might want to open an issue/discussion over there too.

For comparison, the definition used internally in yargs is:

yargs/lib/middleware.ts

Lines 121 to 125 in e517318

export interface MiddlewareCallback {
(argv: Arguments, yargs: YargsInstance):
| Partial<Arguments>
| Promise<Partial<Arguments>>;
}

And for interest related to the internal typings: #1751

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@Jaid @shadowspawn