UrlMatcher is called twice

I’m submitting a…

[ ] Regression (a behavior that used to work and stopped working in a new release)
[x] Bug report  
[ ] Performance issue
[ ] 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

UrlMatcher function is called twice on navigation

Expected behavior

UrlMatcher should be called once

Minimal reproduction of the problem with instructions

https://stackblitz.com/edit/angular-router-basic-example-wdvkbt?file=app/app.routing.module.ts As You can see, on each navigation UrlMatcher is called twice. What’s even weirder is that group argument is different each time - one has parent and one doesn’t.

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

Originally I wanted to create matcher that would match route only if You are in specific named outlet:

export function parentOutletMatcher(outlet: string): UrlMatcher {
	return (segments: UrlSegment[], group: UrlSegmentGroup, route: Route) => {
		if (group.parent && group.parent.children[outlet] === group) {
			return { consumed: [] };
		}
		return null;
	};
}

So I could use one lazy-loaded module to define routes for many named outlets, example:

const ROOT_ROUTES = [
  { path: 'feature', loadChildren: './lazy.module.ts#LazyModule' },
  { path: 'feature', outlet: 'modal', loadChildren: './lazy.module.ts#LazyModule' },
  { path: 'feature', outlet: 'settings', loadChildren: './lazy.module.ts#LazyModule' },
];
// in lazy.module.ts:
const LAZY_ROUTES = [
  { matcher: parentOutletMatcher(PRIMARY_OUTLET), children: [
    // ...
  ]},
  { matcher: parentOutletMatcher('modal'), children: [
    // ...
  ]},
  { matcher: parentOutletMatcher('settings'), children: [
    // ...
  ]},
]

But because of router’s weird behavior this doesn’t work.

Environment

Angular version: 6.1.8

Browser:
- [x] Chrome (desktop) version XX

[Eseperio]

Also happens in 9.1.4

[sambaptista]

Still happening in angular 8.2