JSDoc @augments doesn’t allow function calls to augment existing types
See original GitHub issueI wrote a simple extension of jest.Matchers but I can not get the typescript type checker to recognize my extension.
TypeScript Version: 3.0.1 (and 3.1.0-dev.20180825) The description below is for 3.0.1 - for 3.1.0-dev.20180825 all jest functions show errors, so I don’t even think that the parser gets to my type at all.
[ts] Cannot find name 'describe'.
[ts] Cannot find name 'test'.
[ts] Cannot find name 'expect
Used via vscode version: 1.26.1
Search Terms: is:issue is:open jsdoc extends is:issue is:open jsdoc @augments is:issue is:open jsdoc “@augments”
I first asked this as a question on StackOverflow but after waiting a few days, I now suspect it is a bug in typescript’s JSDoc implementation.
I also read the FAQ and found the link to jest but didn’t find any information there either.
I’m using plain JavaScript and the code runs perfectly.
Code
// @ts-check
const getFunctorValue = F => {
let x
F.fmap(v => x = v)
return x
}
expect.extend({
/**
* @extends jest.Matchers
* @param {*} actual The functor you want to test.
* @param {*} expected The functor you expect.
*/
functorToBe(actual, expected) {
const actualValue = getFunctorValue(actual)
const expectedValue = getFunctorValue(expected)
const pass = Object.is(actualValue, expectedValue)
return {
pass,
message () {
return `expected ${actualValue} of ${actual} to ${pass ? '' : 'not'} be ${expectedValue} of ${expected}`
}
}
}
})
/**
* @param {*} v Any value
*/
function just (v) {
return {
fmap: f => just(f(v))
}
}
describe('Functor Law', () => {
test('equational reasoning (identity)', () => {
expect(just(1)).functorToBe(just(1))
})
})
Expected behavior:
expect().functorToBe
should be recognized as a function.
Actual behavior:
But in the line with expect(just(1)).functorToBe(just(1))
,
I get a red underline under functorToBe
and the following error message:
[ts] Property ‘functorToBe’ does not exist on type ‘Matchers<{ [x: string]: any; fmap: (f: any) => any; }>’. any
I got jest.Matchers
from writing expect()
in vscode and looked at the description.
Playground Link:
Related Issues: No.
Issue Analytics
- State:
- Created 5 years ago
- Reactions:1
- Comments:7 (3 by maintainers)
Top GitHub Comments
Take a look at Module Augmentation on https://www.typescriptlang.org/docs/handbook/declaration-merging.html. Your second idea of merging with Matchers is basically right, I think, since that’s what is returned by
expect
. Your index.d.ts would have to reference jest’s index.d.ts via the name your import it as – probably just'jest'
.Hmm… this doesn’t seem quite right. But I’ll take it to SO and stop polluting this issue.
https://stackoverflow.com/questions/52082800/how-to-describe-the-interface-of-a-simple-just-functor-in-typescript