refactor(types): deduplicate listen options and export it

[kyranet]

The options interface for FastifyInstance.listen was duplicated, which could potentially lead to type signature and documentation differences between the two instances. To solve this, I have made a new interface to unify the two, so there's only one source of truth for both overloads.

I also added export to it because I found it useful - I maintain a library that uses Fastify and it allows users to configure it by passing an object with all the options, which is one of the supported (and non-deprecated) overloads of the listen function. Currently, we would need a very hacky type to get said options from the overloads.

Click to see the code

import type { FastifyInstance } from 'fastify';

export type FastifyObjectOptions = Omit<Exclude<OverloadedParameters<FastifyInstance['listen']>[0], FastifyUnnecessaryUnionTypes>, 'host'>;

/**
 * The union types extracted by {@link Overloads}
 * that we do not want to include in {@link FastifyObjectOptions}
 */
type FastifyUnnecessaryUnionTypes = string | number | ((...args: any[]) => any) | undefined;

/**
 * Extracts the overloads from methods and transforms them into a union
 * source: {@link https://github.com/microsoft/TypeScript/issues/32164#issuecomment-811608386}
 */
type Overloads<T extends (...args: any[]) => any> = T extends {
	(...args: infer A1): infer R1;
	(...args: infer A2): infer R2;
	(...args: infer A3): infer R3;
	(...args: infer A4): infer R4;
	(...args: infer A5): infer R5;
	(...args: infer A6): infer R6;
}
	? ((...args: A1) => R1) | ((...args: A2) => R2) | ((...args: A3) => R3) | ((...args: A4) => R4) | ((...args: A5) => R5) | ((...args: A6) => R6)
	: T extends {
			(...args: infer A1): infer R1;
			(...args: infer A2): infer R2;
			(...args: infer A3): infer R3;
			(...args: infer A4): infer R4;
			(...args: infer A5): infer R5;
	  }
	? ((...args: A1) => R1) | ((...args: A2) => R2) | ((...args: A3) => R3) | ((...args: A4) => R4) | ((...args: A5) => R5)
	: T extends { (...args: infer A1): infer R1; (...args: infer A2): infer R2; (...args: infer A3): infer R3; (...args: infer A4): infer R4 }
	? ((...args: A1) => R1) | ((...args: A2) => R2) | ((...args: A3) => R3) | ((...args: A4) => R4)
	: T extends { (...args: infer A1): infer R1; (...args: infer A2): infer R2; (...args: infer A3): infer R3 }
	? ((...args: A1) => R1) | ((...args: A2) => R2) | ((...args: A3) => R3)
	: T extends { (...args: infer A1): infer R1; (...args: infer A2): infer R2 }
	? ((...args: A1) => R1) | ((...args: A2) => R2)
	: T extends { (...args: infer A1): infer R1 }
	? (...args: A1) => R1
	: never;

/**
 * Extracts the overloaded parameters from methods
 * source: {@link https://github.com/microsoft/TypeScript/issues/32164#issuecomment-811608386}
 */
type OverloadedParameters<T extends (...args: any[]) => any> = Parameters<Overloads<T>>;

So for ease of development, I think this export would be beneficial, not for us, but quite possibly for a lot of people as well.

Checklist

• run npm run test and npm run benchmark
• tests and/or benchmarks are included
• documentation is changed or added
• commit message and code follows the Developer's Certification of Origin
  and the Code of conduct

[kyranet]

This was moved due to VSCode's auto-import, should I leave it as-is, or move it back to the top? 😅

[climba03003]

I am ok with this change

[mcollina]

lgtm

[mcollina]

I'm so sorry, I didn't merge straight away, and now this conflicts. Could you rebase?

[climba03003]

LGTM.

[kyranet]

I'm so sorry, I didn't merge straight away, and now this conflicts. Could you rebase?

No worries, I have just rebased the PR :)

Edit: I made a second force push to add a missing space from the original code.

[mcollina]

lgtm

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