hostDirectives deep input mapping works implicitly and not explicitly about angular HOT 3 OPEN

To understand the behavior, it's worth keeping in mind that host directives are all resolved to a flat array during matching, instead of being treated as a tree. E.g. in your example Angular would match [Level3, Level2, Level1], rather than [Level3, [Level2, [Level1]]]. In this context forwarding inputs multiple levels doesn't make sense, because there is no hierarchy.

As for this example:

What more this actually works:

@directive({
selector: '[level3]',
standalone: true,
hostDirectives: [{ directive: Level2Directive }],
})
export class Level3Directive {}
and exposes input of Level2Directive implicitly

Unless I'm missing something, that works because background is exposed from Level1Directive which was brought in by Level2Directive.

from angular.

Say I use an directive from some lib:

1. It has it's own inputs - well I can reuse it as hosted directive, reassigning input names, and even add diffrent hosted directive from some other lib that have the same input names but change them so they won't colllide.
2. It has hosted directive and only reexports it, hard luck - now we cannot reassigning input names and use if with diffrent hosted directive - solution - do not use it or ask library author to change the way he implemented the directive - simply do not use hosted directives.

So basicly You need to look into implementation details of directives to knwon what can be done with them.

I would expect that hosted directive inputs/outputs are always resolved in the same way, so it would be transparent for user of lib whatever hosted directive was used or not to create some input.

Also TS-992017: Directive Level2Directive does not have an input with a public name of background. is misleading as You can actually set input background on Level2Directive directive in html tempalte so it kinda does have that input.

You see confusion - sometimes input exist sometimes it does not.

If needed I can provide more examples in stackblitz of all the cases I mentioned in my posts.

from angular.

We can definitely do a better job at documenting the behavior, but I think it's consistent. The directives aren't really "mixed in", but rather they just get applied one after the other. The Directive Level2Directive does not have an input with a public name of background. error is correct, because the background input in that case writes to an instance of Level1Directive.

from angular.