Several commits for resource() #59024
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| request.set(undefined); | ||
| expect(echoResource.status()).toBe(ResourceStatus.Idle); | ||
| }); | ||
| it('set() should abort a pending load', async () => { |
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mega-nit: new line to add spacing between tests
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I really like the defaultValue on resource. Having not an Thanks for that! |
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Originally the `T` in `Resource<T>` represented the resolved type of the resource, and `undefined` was explicitly added to this type in the `.value` signal. This turned out to be problematic, as it wasn't possible to write a type for a resource which didn't return `undefined` values. Such a type is useful for 2 reasons: 1. to support narrowing of the resource type when `Resource.hasValue()` returns `true`. 2. for resources which use a different value instead of `undefined` to represent not having a value (for example, array resources which want to use `[]` as their default). Instead, this commit changes `resource()` and `rxResource()` to return an explicit `ResourceRef<T|undefined>`, and removes the union with `undefined` from all types related to the resource's value. This way, it's trivially possible to write `Resource<T>` to represent resources where `.value` only returns `T`. `hasValue()` then actually works to perform narrowing, by narrowing the resource type to `Exclude<T, undefined>`.
When the reactive `request` of a resource() notifies, it transitions to the
Loading state, fires the loader, and eventually transitions to Resolved.
With the prior implementation, a change of the `request` will queue the
effect, but the state remains unchanged until the effect actually runs. For
a brief period, the resource is in a state where the request has changed,
but the state has yet to update.
This is problematic if we want to use resources in certain contexts where we
care about the state of the resource in a synchronous way. For example, an
async validator backed by a resource might be checked after an update:
```
value.set(123);
if (validator.value()) {
// value is still valid, even though the resource is dirty and will soon
// flip to loading state (returning value(): undefined) while revalidating
}
```
To address this timing concern, `linkedSignal()` is used within the
`resource()` to synchronously transition the state in response to the
request changing. This ensures any followup reads see a consistent view of
the resource regardless of whether the effect has run.
This also addresses a race condition where `.set()` behaves differently on a
`resource()` depending on whether or not the effect has run.
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Caretaker: this PR is sensitive to backsliding. we need to patch cl/716243172 so far (and potentially more depending on presubmit failures). |
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This PR was merged into the repository by commit 01fffdb. The changes were merged into the following branches: main, 19.1.x |
AndrewKushnir
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Jan 16, 2025
…gs (#59024) Originally the `T` in `Resource<T>` represented the resolved type of the resource, and `undefined` was explicitly added to this type in the `.value` signal. This turned out to be problematic, as it wasn't possible to write a type for a resource which didn't return `undefined` values. Such a type is useful for 2 reasons: 1. to support narrowing of the resource type when `Resource.hasValue()` returns `true`. 2. for resources which use a different value instead of `undefined` to represent not having a value (for example, array resources which want to use `[]` as their default). Instead, this commit changes `resource()` and `rxResource()` to return an explicit `ResourceRef<T|undefined>`, and removes the union with `undefined` from all types related to the resource's value. This way, it's trivially possible to write `Resource<T>` to represent resources where `.value` only returns `T`. `hasValue()` then actually works to perform narrowing, by narrowing the resource type to `Exclude<T, undefined>`. PR Close #59024
AndrewKushnir
pushed a commit
that referenced
this pull request
Jan 16, 2025
When the reactive `request` of a resource() notifies, it transitions to the
Loading state, fires the loader, and eventually transitions to Resolved.
With the prior implementation, a change of the `request` will queue the
effect, but the state remains unchanged until the effect actually runs. For
a brief period, the resource is in a state where the request has changed,
but the state has yet to update.
This is problematic if we want to use resources in certain contexts where we
care about the state of the resource in a synchronous way. For example, an
async validator backed by a resource might be checked after an update:
```
value.set(123);
if (validator.value()) {
// value is still valid, even though the resource is dirty and will soon
// flip to loading state (returning value(): undefined) while revalidating
}
```
To address this timing concern, `linkedSignal()` is used within the
`resource()` to synchronously transition the state in response to the
request changing. This ensures any followup reads see a consistent view of
the resource regardless of whether the effect has run.
This also addresses a race condition where `.set()` behaves differently on a
`resource()` depending on whether or not the effect has run.
PR Close #59024
AndrewKushnir
pushed a commit
that referenced
this pull request
Jan 16, 2025
When the reactive `request` of a resource() notifies, it transitions to the
Loading state, fires the loader, and eventually transitions to Resolved.
With the prior implementation, a change of the `request` will queue the
effect, but the state remains unchanged until the effect actually runs. For
a brief period, the resource is in a state where the request has changed,
but the state has yet to update.
This is problematic if we want to use resources in certain contexts where we
care about the state of the resource in a synchronous way. For example, an
async validator backed by a resource might be checked after an update:
```
value.set(123);
if (validator.value()) {
// value is still valid, even though the resource is dirty and will soon
// flip to loading state (returning value(): undefined) while revalidating
}
```
To address this timing concern, `linkedSignal()` is used within the
`resource()` to synchronously transition the state in response to the
request changing. This ensures any followup reads see a consistent view of
the resource regardless of whether the effect has run.
This also addresses a race condition where `.set()` behaves differently on a
`resource()` depending on whether or not the effect has run.
PR Close #59024
PrajaktaB27
pushed a commit
to PrajaktaB27/angular
that referenced
this pull request
Feb 7, 2025
…gs (angular#59024) Originally the `T` in `Resource<T>` represented the resolved type of the resource, and `undefined` was explicitly added to this type in the `.value` signal. This turned out to be problematic, as it wasn't possible to write a type for a resource which didn't return `undefined` values. Such a type is useful for 2 reasons: 1. to support narrowing of the resource type when `Resource.hasValue()` returns `true`. 2. for resources which use a different value instead of `undefined` to represent not having a value (for example, array resources which want to use `[]` as their default). Instead, this commit changes `resource()` and `rxResource()` to return an explicit `ResourceRef<T|undefined>`, and removes the union with `undefined` from all types related to the resource's value. This way, it's trivially possible to write `Resource<T>` to represent resources where `.value` only returns `T`. `hasValue()` then actually works to perform narrowing, by narrowing the resource type to `Exclude<T, undefined>`. PR Close angular#59024
PrajaktaB27
pushed a commit
to PrajaktaB27/angular
that referenced
this pull request
Feb 7, 2025
When the reactive `request` of a resource() notifies, it transitions to the
Loading state, fires the loader, and eventually transitions to Resolved.
With the prior implementation, a change of the `request` will queue the
effect, but the state remains unchanged until the effect actually runs. For
a brief period, the resource is in a state where the request has changed,
but the state has yet to update.
This is problematic if we want to use resources in certain contexts where we
care about the state of the resource in a synchronous way. For example, an
async validator backed by a resource might be checked after an update:
```
value.set(123);
if (validator.value()) {
// value is still valid, even though the resource is dirty and will soon
// flip to loading state (returning value(): undefined) while revalidating
}
```
To address this timing concern, `linkedSignal()` is used within the
`resource()` to synchronously transition the state in response to the
request changing. This ensures any followup reads see a consistent view of
the resource regardless of whether the effect has run.
This also addresses a race condition where `.set()` behaves differently on a
`resource()` depending on whether or not the effect has run.
PR Close angular#59024
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