fix(defer) Disallow passing () => undefined to observableFactory #5449
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added 2 commits
May 20, 2020 12:20
benlesh
reviewed
May 20, 2020
| @@ -28,6 +28,10 @@ it('should error if function returns undefined', () => { | |||
| const a = defer(() => undefined); // $ExpectError | |||
| }); | |||
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| it('should error if function returns never', () => { | |||
| const a = defer(() => { throw new Error(); }); // $ExpectError | |||
| }); | |||
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Does this work?
defer(() => {
if (Math.random() > 0.5) {
throw new Error();
}
return of(1, 2, 3);
});I mean, I assume it does, but It would be nice to have a test there.
cartant
requested changes
May 20, 2020
| export function defer<R extends ObservableInput<any> | void>(observableFactory: () => R): Observable<ObservedValueOf<R>> { | ||
| export function defer<R extends ObservableInput<any> | void>( | ||
| observableFactory: [R] extends [undefined] | [void] ? never : () => R | ||
| ): Observable<ObservedValueOf<R>> { |
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IMO, if we are going to fix this footgun, we should only be accepting factories that return a valid ObservableInput. I think the fix should be the removal of the void:
export function defer<R extends ObservableInput<any>>(observableFactory: () => R): Observable<ObservedValueOf<R>> { ...And I think the implementation should be changed, too. If it's not, the footgun is still there for non-TS usage.
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I agree. It's weird that we ever had this work.
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Done, I've updated the tests and dstlint spec to reflect the changes
benlesh
approved these changes
Jun 15, 2020
This was referenced Dec 8, 2022
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fixes #5446