The current Router APIs require guards/resolvers to be present in the DI tree. This is because we want to treat all guards/resolvers equally and some may require dependencies. This requirement results in quite a lot of boilerplate for guards. Here are two examples:
```
const MY_GUARD = new InjectionToken<any>('my_guard');
…
providers: {provide: MY_GUARD, useValue: () => window.someGlobalState}
…
const route = {path: 'somePath', canActivate: [MY_GUARD]}
```
```
@Injectable({providedIn: 'root'})
export class MyGuardWithDependency {
constructor(private myDep: MyDependency) {}
canActivate() {
return myDep.canActivate();
}
}
…
const route = {path: 'somePath', canActivate: [MyGuardWithDependency]}
```
Notice that even when we want to write a simple guard that has no dependencies as in the first example, we still have to write either an InjectionToken or an Injectable class.
With this commit router guards and resolvers can be plain old functions.
For example:
```
const route = {path: 'somePath', component: EditCmp, canDeactivate: [(component: EditCmp) => !component.hasUnsavedChanges]}
```
Additionally, these functions can still use Angular DI with `inject` from `@angular/core`.
```
const route = {path: 'somePath', canActivate: [() => inject(MyDependency).canActivate()]}
```
PR Close#46684
The existing logic does something similar but in a more roundabout way.
It reads _the whole array_. If it encounters a pending value, it ignores
the remaining ones. If it hasn't encountered a pending value by the time
it hits false/UrlTree, it returns that result.
The new logic is the same, but reverses what we're looking for. Instead
of processing the whole array, we stop when we encounter an initial
value. When we encounter one that isn't `true`, that gets returned. If
we get to the end and everything was `true`, return `true`.
PR Close#46745
PR Close#46745
Recently the navigation was on hold even at least one resolver didn't emit any value and completed, but another ones still are in progress to resolve any value. The changes cancel the navigation instantly if at least one resolver doesn't emit any value and completed.
PR Close#45621
The router used to wait for the resolvers to complete and take the last
value. The changes here take only the first
emitted value of every resolver and proceed the navigation. This matches
how other guards work in the `Router` code.
Resolves https://github.com/angular/angular/issues/44643
BREAKING CHANGE: Previously, resolvers were waiting to be completed
before proceeding with the navigation and the Router would take the last
value emitted from the resolver.
The router now takes only the first emitted value by the resolvers
and then proceeds with navigation. This is now consistent with `Observables`
returned by other guards: only the first value is used.
PR Close#44573
This change aligns behavior for resolvers which return EMPTY. Currently EMPTY resolvers have inconsistent behavior:
- One resolver that returns EMPTY => won't navigate and just ends on ResolveStart router event.
- Two resolvers where both return EMPTY => throws "Error: Uncaught (in promise): EmptyError: no elements in sequence"
- Two resolvers where one returns a value and the other one returns EMPTY => Navigates successfully.
With this change any EMPTY resolver will cancel navigation.
BREAKING CHANGE: Any resolver which return EMPTY will cancel navigation.
If you want to allow the navigation to continue, you will need to update the resolvers to emit
some value, (i.e. defaultIfEmpty(...), of(...), etc).
PR Close#24195
PR Close#24621
* If all guards return `true`, operator returns `true`
* `false` and `UrlTree` are now both valid returns from a guard
* Both these values wait for higher priority guards to resolve
* Highest priority `false` or `UrlTree` value will be returned
PR Close#26478
