Fix service typings

[Bassel17]

What does it do?

• Adds a GenericService type that allows the creation of custom services

How to test it?

• Try to add a custom service it should work just fine and not throw an error

Related issue(s)/PR(s)

Fixes #14035

[alexandrebodin]

You will also want to change the service declaration in packages/core/strapi/lib/global.d.ts :)

[codecov]

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[pwizla]

Hi! I guess this would not require any documentation update, it will just fix things, so they work as documented in Backend customization > Services, right?

[Bassel17]

Hi! I guess this would not require any documentation update, it will just fix things, so they work as documented in Backend customization > Services, right?

@pwizla yep correct, just trying to fix the types, the documentation will stay the same

switch reviewer

[Convly]

It won't necessarily return an Entity here 🙂

[Bassel17]

hmmmm, should we have it be any or unknown ?

[stafyniaksacha]

Can use a generic here:
[method: string | number | symbol]: <T = unknown>(...args:unknown) => T;

and may be better to use any over unknown for now since we can't have a strict type checking until we have a good typing coverage
[method: string | number | symbol]: <T = any>(...args:any) => T;

[Bassel17]

@stafyniaksacha agreed probably using any would be better for now, will go with your suggestion

[eucciferri]

Hi @Bassel17! How are you?

I updated to the latest version and all my methods now throw me an error:

I looked for the definitions file and I modified the return type of the methods as follows:

After doing this everything works perfectly, even the custom services methods (which was the reason that generated this fix).

Is it possible for you to modify the return type?

Thanks!

[eucciferri]

Perhaps a return type like the following is more comprehensive:

export type GenericService = Partial<Service> & {
   [method: string | number | symbol]: <T = any>(...args: any) => Promise<Entity | Entity[] | void> | Entity | Entity[] | void;
};

[Bassel17]

@eucciferri it was already making an issue before which is why we made the return value into "any" or whatever the person chooses to type it, I'll check again

[stafyniaksacha]

Is it possible for you to modify the return type?

No the error is good! It says that you have miss typed the findOne method: You used a string type whereas it needs a number for the entityId

[stafyniaksacha]

For now to properly infer types while using createCoreService, this is what I use:

import type {
  CollectionTypeService,
  Service,
} from '@strapi/strapi/lib/core-api/service';

import { Strapi, factories } from '@strapi/strapi';

const custom = ({ strapi }: { strapi: Strapi }) => ({
  async foo() { return 'a string' }
  async bar() { return 42 }
})

const base = factories.createCoreService(
  'plugin::shopify.fulfillment-order',
  custom as Service
);

// this allow typescript to infer `foo` & `bar` functions with base `find`/`findOne`/....
export default base as () => CollectionTypeService & ReturnType<typeof custom>;

You can check the Extends global strapi typings part of this PR: https://github.com/strapi/documentation/pull/1078/files#diff-9d134c2a40e37f7e5758ffff7bb9a3d4bc6999494929d54d65d52f7db66cd2a0R94-R188

[stafyniaksacha]

Here is a shims for dynamic createCoreService method:

import {
  Service,
  SingleTypeService,
  CollectionTypeService,
} from '@strapi/strapi/lib/core-api/service';

declare module '@strapi/strapi/lib/types/factories' {
  export interface ServiceUidMap {
    'plugin::foo.bar': CollectionTypeService; 
    'api::homepage.homepage': SingleTypeService; 
    [key: string]: Service;
  }

  export function createCoreService<K extends keyof ServiceUidMap, T>(
    uid: K,
    customActions?: T
  ): T extends undefined
    ? () => ServiceUidMap[K] // only base service
    : T extends (...args: any) => any // custom action is function ? ({ strapi }) => ({})
    ? () => ReturnType<T> & ServiceUidMap[K] // merge custom action return type 
    : () => T & ServiceUidMap[K];
}

export {};

[eucciferri]

No the error is good! It says that you have miss typed the findOne method: You used a string type whereas it needs a number for the entityId

Hi @stafyniaksacha! How are you?

The error is reproduced regardless of the type of data that I place in the attributes, even if it is a "string", "number" or "any".

The only solution I found, as I mentioned in my previous post, was to specify the type of response that the method can throw, so I placed a Promise (in case an async method is created) of an Entity, an array of Entities or a void (in case nothing is returned).

This error is always reproduced, even if you create a project from scratch and follow all the steps as indicated in the documentation, to create a new method or overwrite an existing one.

Strapi Documentation

Thanks.

[emahuni]

The error is still happening, however, doing the following fixes it I have no idea if this is desirable or not, coz I think it's up to the to decide the return type:

putting any as the return type completely fixed the issue such that everything works without a problem:

export type GenericService = Partial<Service> & {
  [method: string | number | symbol]: <T = any>(...args: any) => any;
};


export default factories.createCoreService('api::something.something', ({ strapi })  => {
  return {
    // service functions or properties here
    async someFunction (a: number): Promise<number[]> {
      return [1, 2, 3];
    },
    
    async someFunction2<T> (a: number): Promise<T[]> {
      return [1 as T]; // to show example
    },
  };
});

notice the generic example at the end still works, so I am assuming that anything that is returned should work.

[eucciferri]

Hi @emahuni, yes, it keeps getting the error for me too. I had to migrate all my services files to JavaScript in order to resolve this error.

@stafyniaksacha @Bassel17 Hi guys! Could you please review this issue?

[stafyniaksacha]

Hello @eucciferri!

I created two PR here:

• fix(typescript): use declaration merging for factories utilities #14222
• fix(typescript): removes global Strapi namespace and use internal types #14219

[eucciferri]

Great news @stafyniaksacha! Thank you so much!! 😃