Solvedangular Change Route guard and resolver ordering to follow route parent/child hierarchy

I'm submitting a...

[ ] Regression (a behavior that used to work and stopped working in a new release)
[ ] Bug report  
[ ] Performance issue
[x] Feature request
[ ] Documentation issue or request
[ ] Support request => Please do not submit support request here, instead see https://github.com/angular/angular/blob/master/CONTRIBUTING.md#question
[ ] Other... Please describe:

Current behavior

Resolve blocks are processed only distinctly after all guards are finished, meaning guards cannot protect routes that rely on asynchronous data (i.e. fetching the user) without breaking the guard/resolver paradigm.

Expected behavior

Process guards before resolvers, but follow the route parent -> child hierarchy; allow parent data to be loaded before processing authorization for child routes.

Minimal reproduction of the problem with instructions

StackBlitz: https://angular-gitter-cui2tq.stackblitz.io

Click the inline link at the top, which will attempt to load the "/somewhere" route; however, since the parent's resolver does not fire before the child's guard, the user will be undefined and you'll be redirected to the "/elsewhere" route.

What is the motivation / use case for changing the behavior?

The guard/resolver dichotomy crumbles with asynchronous data and does not allow for proper segregation of duties as described in the documenation; either guards must load data AND handle authorization, or resolvers must load data AND handle authorization. As it stands, you cannot use both as all guards are always processed first.

I actually wrote a complete breakdown in #15026, comment here -- this is probably the best explanation of why this is an issue that I can provide.

Environment

Angular version: 6.0.3


Browser:
- [x] Chrome (desktop) version XX
- [ ] Chrome (Android) version XX
- [ ] Chrome (iOS) version XX
- [ ] Firefox version XX
- [ ] Safari (desktop) version XX
- [ ] Safari (iOS) version XX
- [ ] IE version XX
- [ ] Edge version XX
 
For Tooling issues:
- Node version: 8.11.2  
- Platform:  MacOS

Others:
22 Answers

✔️Accepted Answer

To keep the info inside this ticket and easy to read, below is a copy of #15026 (comment) by @SamuelMS


This generally defeats the purpose of route guards for async dependencies.

Imagine this use-case:

// loaded in the root app router
const appRoutes: Routes = [
    {
        path: '',
        resolve: {
            config: ConfigResolver,
            user: UserResolver,
        },
        children: [
            { path: 'error', component: ErrorComponent },
            {
                path: 'somewhere',
                loadChildren: 'app/somewhere/somewhere.module#SomewhereModule'
            },
            {
                path: 'elsewhere',
                loadChildren: 'app/elsewhere/elsewhere.module#ElsewhereModule'
            },
            { path: '**', redirectTo: 'somewhere' }
        ]
    },
    { path: '**', redirectTo: '' }
];

// loaded in a fictional "somewhere" router
const somewhereRoutes: Routes = [
    {
        path: '',
        resolve: {
            userWorkspace: UserWorkspaceResolver,
        },
        children: [
            {
                path: '',
                component: WorkspaceDetailComponent,
                canActivateChild: [ WorkspaceDetailGuard ],
                children: [
                    // ...
                ],
            },
            {
                path: 'onboarding',
                component: WorkspaceOnboardingComponent,
                canActivateChild: [ WorkspaceOnboardingGuard ],
                children: [
                    // ...
                ],
            },
            { path: '**', redirectTo: '' }
        ]
    },
    { path: '**', redirectTo: '' }
];

Pretty simple. Two relevant modules: the root "app" module and a lazy-loaded "somewhere" module. Pardon the naming.

A bunch of top-level information is resolved at the highest-order routes, and then more information about some fictional "workspace" is resolved within the somewhere module.

Here's the catch: the "WorkspaceDetailGuard" and "WorkspaceOnboardingGuard" guards are dependent on the workspace resolved at a parent route (via UserWorkspaceResolver), which in turn is dependent on the user data loaded even before then (via UserResolver).

Per the explanations in this thread, this will never work as-is, since guards (CanActivate, CanActivateChild, etc) are always processed before resolvers can even begin their work. This makes sense if you ask "why start loading data before we know the user can even activate XYZ route" -- but only from a strictly synchronous standpoint; there's no reason to assume users will have all the information they need to properly "guard" routes before they make any asynchronous calls.

So, the apparent solution from this issue is to convert all async guards to resolvers, and do work in them -- or convert all resolvers to guards -- so that they fire in hierarchical order and can properly depend on each other. But this is not intuitive at all from a segregation of duties standpoint: guards are meant to handle authorization, and resolvers load data. In either of these scenarios, you're essentially using one or the other, but not both; you'll have guards that load data, or you'll have resolvers that handle authorization. This is backwards and is confusing.

Let me know if I'm misunderstanding something here; otherwise, I'd like to re-open this ticket and suggest that Angular handle guards first, then resolvers, but follow the parent -> child route hierarchy; in other words, guarantee that parent route data is resolved before child route logic fires.

Other Answers:

Any updates?

I'm going crazy trying to find a scalable solution. The current evaluation order cannot work decently in enterprise size applications with dozens (or hundreds) of routes.

Any update on this?

I am upvoting this.
OP's desired behavior is more smooth and clear that the current one.
Stuck in the same situation when resolver fits its place, but i cannot use it because child activation guards triggers first.

In my situation i am able to workaround this with replacing Resolve with CanActivate, but i will got a side effect then - guards will be triggered on child routes redirects. So it's likely that i will receive the same data twice if i will use this workaround.

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