test(dtslint): add dtslint test on count operator (#4093) #4139
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spec-dtslint/operators/count-spec.ts
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| import { count } from 'rxjs/operators'; | ||
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| it('should always infer number', () => { | ||
| const o = of(1, 2, 3).pipe(count(x => x > 1)); // $ExpectType Observable<number> |
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I believe we should also test the predicate overloads.
predicate: (value: T, index: number, source: Observable<T>)There was a problem hiding this comment.
Added few more tests around the predicate overloads types.
Please let me know if they are of a good value.
Thanks
spec-dtslint/operators/count-spec.ts
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| }); | ||
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| it('should expect function parameter', () => { | ||
| const o = of(1, 2, 3).pipe(count(9)); // $ExpectError |
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We should also test if the value is the same type as the source.
For example
const o = of(1, 2, 3).pipe(count((value: string) => value !== ''); // $ExpectError
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spec-dtslint/operators/count-spec.ts
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| import { count, buffer } from 'rxjs/operators'; | ||
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| it('should always infer number', () => { | ||
| const o = of(1, 2, 3).pipe(count(x => x > 1)); // $ExpectType Observable<number> |
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With count, the return type of the piped observable will always be Observable<number>, so I think that for at least one of the tests, the source observable type should be something other than number - to make sure that the output type comes from the count operator and not the source. E.g.:
const o = of('1', '2', '3').pipe(count(x => x !== '1')); // $ExpectType Observable<number>There was a problem hiding this comment.
@cartant I have added another row to both number or string will always return number
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Description: Add count dtslint test
Related issue (if exists): #4093