VSCode does not recognize jest custom matcher - jestjs

Question

I'm currently struggling with making a Jest custom matcher work in VSCode with typescript.
I wrote a custom matchers file like the following (I've simplified the test for brevity reasons):
export {}
declare global {
namespace jest {
interface Matchers<R, T = {}> {
toSucceed(): R
}
}
}
function toSucceed(this: jest.MatcherContext, received: Result<any>): any {
return {
pass: true,
message: () => 'Custom matcher message',
}
}
expect.extend({
toSucceed,
})
I included this file path in my jest.config.ts under the tag setupFilesAfterEnv.
Then I wrote tests like:
it('should pass', () => {
expect(foo()).toSucced()
})
All this configuration works fine, but I still get a VSCode inline error:
Property 'toSucceed' does not exist on type 'JestMatchers<any>'
JestMatchers is a type definition inside the #types/jest root, since it is a type I cannot augment it directly.
Have anyone experienced any similar problem?

Answer 1

I encountered a similar error message when the namespace declaration of "interface Matchers" was incorrect. After fixing that, a custom matcher appeared in jestMatchers, too. Matchers and jestMatchers are connected.
Your code works fine for me—except for the undefined Result<any>—so you can try to directly import in test and see if Visual Studio Code can understand the declaration:
import "./toSucceed";
If direct import works for you, I would guess that there's a problem with the jest extension which helps Visual Studio Code understand jest.config.

Answer 2

Did you remember to add the type definitions to your tsconfig?
For me it works fine when I put the type definition in a d.ts file at the root level, and add that path to the "include" option in my tsconfig:
{
// Some other config
"include": [
"custom-matchers.d.ts"
]
}
Haven't tested with your custom matcher specifically, but I had a similar issue that I resolved like this.
So your custom-matchers.d.ts would be:
export {}
declare global {
namespace jest {
interface Matchers<R, T = {}> {
toSucceed(): R
}
}
}