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When a resource first starts up, even if it transitions immediately to `Loading` it should report a `previous.state` of `Idle`. It was reporting `Loading` as the previous state in such a case because of an oversight in the migration to `linkedSignal` which this commit addresses.
`hasValue` attempts to narrow the type of a resource to exclude `undefined`. Because of the way signal types merge in TS, this only works if the type of the resource is the same general type as `hasValue` asserts. For example, if `res` is `WritableResource<string|undefined>` then `.hasValue()` correctly asserts that `res` is `WritableResource<string>` and `.value()` will be narrowed. If `res` is `ResourceRef<string|undefined>` then that narrowing does _not_ work correctly, since `.hasValue()` will assert `res` is `WritableResource<string>` and TS will combine that for a final type of `ResourceRef<string|undefined> & WritableResource<string>`. The final type of `.value()` then will not narrow. This commit fixes the above problem by adding a `.hasValue()` override to `ResourceRef` which asserts the resource is of type `ResourceRef`. Fixes angular#59707
thePunderWoman
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Jan 24, 2025
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JeanMeche
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Jan 24, 2025
| * @experimental | ||
| */ | ||
| export interface ResourceRef<T> extends WritableResource<T> { | ||
| hasValue(): this is ResourceRef<Exclude<T, undefined>>; |
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Should we maybe capture this in a test ?
AndrewKushnir
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kirjs
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This PR was merged into the repository by commit 6c92d65. The changes were merged into the following branches: main |
pkozlowski-opensource
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Jan 28, 2025
`hasValue` attempts to narrow the type of a resource to exclude `undefined`. Because of the way signal types merge in TS, this only works if the type of the resource is the same general type as `hasValue` asserts. For example, if `res` is `WritableResource<string|undefined>` then `.hasValue()` correctly asserts that `res` is `WritableResource<string>` and `.value()` will be narrowed. If `res` is `ResourceRef<string|undefined>` then that narrowing does _not_ work correctly, since `.hasValue()` will assert `res` is `WritableResource<string>` and TS will combine that for a final type of `ResourceRef<string|undefined> & WritableResource<string>`. The final type of `.value()` then will not narrow. This commit fixes the above problem by adding a `.hasValue()` override to `ResourceRef` which asserts the resource is of type `ResourceRef`. Fixes #59707 PR Close #59708
PrajaktaB27
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Feb 7, 2025
When a resource first starts up, even if it transitions immediately to `Loading` it should report a `previous.state` of `Idle`. It was reporting `Loading` as the previous state in such a case because of an oversight in the migration to `linkedSignal` which this commit addresses. PR Close angular#59708
PrajaktaB27
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to PrajaktaB27/angular
that referenced
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Feb 7, 2025
`hasValue` attempts to narrow the type of a resource to exclude `undefined`. Because of the way signal types merge in TS, this only works if the type of the resource is the same general type as `hasValue` asserts. For example, if `res` is `WritableResource<string|undefined>` then `.hasValue()` correctly asserts that `res` is `WritableResource<string>` and `.value()` will be narrowed. If `res` is `ResourceRef<string|undefined>` then that narrowing does _not_ work correctly, since `.hasValue()` will assert `res` is `WritableResource<string>` and TS will combine that for a final type of `ResourceRef<string|undefined> & WritableResource<string>`. The final type of `.value()` then will not narrow. This commit fixes the above problem by adding a `.hasValue()` override to `ResourceRef` which asserts the resource is of type `ResourceRef`. Fixes angular#59707 PR Close angular#59708
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2 fixes for
resource()