test(dtslint): add dtslint test for scan operator (#4093) #4347
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Pull Request Test Coverage Report for Build 7645
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spec-dtslint/operators/scan-spec.ts
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| it('should infer correctly with Array of T value', () => { | ||
| const a = of(1, 2, 3).pipe(scan((acc: number[], val: number, i) => [...acc, val])); // $ExpectType Observable<number[]> |
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Without a seed of [] this should effect an error. It's a flaw in the typings. I'd add the []. I'll look at fixing the scan and reduce typings later; it's on my TODO list.
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I'll be good if you could tag me when you do a PR for this. I'd like to learn how to resolve this kind of problem. Thanks Nick!
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The typings for scan and reduce have issues. These will be addressed at a later date.
The simplest thing to do with these tests would be to replace them with the tests that were written for reduce, but change the operators and change the type expectations to be arrays instead of the the reduced values - e.g. Observable<number[]> instead of Observable<number>, etc.
More comprehensive tests can be written when the issues with the typings are addressed.
spec-dtslint/operators/scan-spec.ts
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| it('should infer correctly with type change accumulator', () => { | ||
| const a = of(1, 2, 3).pipe(scan((acc: string, val: number, i) => `${acc} ' ' ${val}`)); // $ $expectType Observable<string> |
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| it('should infer correctly for accumulator of type array', () => { | ||
| const a = of(1, 2, 3).pipe(scan((x: number[], y: number, i: number) => x, [])); // $ExpectType Observable<number[]> |
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Hi @cartant ,
I have changed the test to identically like reduce. But, I'm not sure about the type expectations you mentioned on the comment above - look like the typings are exactly the same as reduce.
Is this correct?
Description: Add dtslint test for Scan operator
Related issue (if exists): #4093