Add custom type to DefinitelyTyped

[RicardoJBarrios]

Feature Request

Description:

When use Jest and jest-expect-message with Typescript the compiler always display an error because Expect interface only accept one argument in the definition from DefinitelyTyped, but tests works as expected.

Possible solution:

For a temporal workaround I have added <T = any>(actual: T, customMessage?: string): Matchers<T>; to the Expect interface in @types/jest/index.d.ts, but it could be added as an extension to DefinitelyTyped.

[sabrehagen]

Could this be added to this library so that when it is imported it extends jest's types?

[mattphillips]

Hey @RicardoJBarrios I don't use Typescript, is it possible to do as @sabrehagen suggested and add the type definition to this project and override Jest's types? Happy to accept any help with this :)

[sabrehagen]

I tried placing the below snippet in node_modules/jest-expect-message/typings.d.ts and adding the "types": "typings.d.ts" field to the jest-expect-message package.json but the merged declaration was not picked up. Any idea on how to support this 'unofficial' type through this package?

declare namespace jest {
  interface Expect {
    <T = any>(actual: T, message?: string): Matchers<T>;
  }
}

[drewxiuxiuxiu]

As far as I know there is no (or at least, elegant) way, to override an existing type.
My suggestion is: in setup script, instead of overwrite global.expect, use another name e.g. global.expectWithMsg.

It basically changes nothing.

import withMessage from 'jest-expect-message/dist/withMessage'
global.expectWithMsg = withMessage(expect)

then declare your type anywhere else within a .d.ts:

declare const expectWithMsg: <T>(actual: T, msg: string) => Matchers<T>

[quezak]

For anyone looking for a quick & clean workaround -- I patched jest typings with patch-package, to be placed under patches/@types/jest+23.3.13.patch

patch-package
--- a/node_modules/@types/jest/index.d.ts
+++ b/node_modules/@types/jest/index.d.ts
@@ -448,7 +448,9 @@ declare namespace jest {
          *
          * @param actual The value to apply matchers against.
          */
-        <T = any>(actual: T): Matchers<T>;
+        // Patched declaration to support jest-expect-message
+        // TODO monitor https://github.com/mattphillips/jest-expect-message/issues/1 for an actual solution
+        <T = any>(actual: T, customMessage?: string): Matchers<T>;
         /**
          * Matches anything but null or undefined. You can use it inside `toEqual` or `toBeCalledWith` instead
          * of a literal value. For example, if you want to check that a mock function is called with a

[yss14]

@sabrehagen Your type declaration seems fine to me.
jest-extended also provide their type declaration this way and it seems to work for them.
Maybe /// <reference types="jest" /> somehow tells TS to merge declarations?

[yss14]

Found the trick

[mike-d-davydov]

This is what worked for me:

Create @types folder in your node project
put there jest-expect-message.d.ts:

export {}

declare global {
	namespace jest {
		interface Expect{
			<T = any>(actual: T, message:String): Matchers<T>;
		}
	}
}

Here is a sample project: https://github.com/mike-d-davydov/typedef-jest-expect-message .

That is pretty much it. I am also trying to push this definition to Definitely Typed: DefinitelyTyped/DefinitelyTyped#34890. Please kindly let me know if there are any comments/suggestions how to improve.

Will update when done.

[mike-d-davydov]

@mattphillips , please kindly take a look: DefinitelyTyped/DefinitelyTyped#34890. It seems like I may need an author approval for this to get through... Thanks!

[maoueh]

Thanks @mike-d-davydov, seems to work out of the box now by installing:

yarn add --dev @types/jest-expect-message

Thanks for pushing it to DefinitelyTyped repo!

[jasperkuperus]

Works for me! Guess this issue can be closed?

[pieterdb4477]

Great, it might be a good idea to add this to the main readme.

[horttanainen]

@mike-d-davydov should not the message field be optional?

Like so:

declare namespace jest {
    interface Expect {
        <T = any>(actual: T, message?: string): Matchers<T>;
    }
}

[DonIsaac]

@mattphillips are you still maintaining this package?

[mattphillips]

I've added a typescript setup instructions to the readme: https://github.com/mattphillips/jest-expect-message#configure-typescript and defined the types as part of this library so will go ahead and close this.