Loosen validator directives selectors

[Xriuk]

Which @angular/* package(s) are relevant/related to the feature request?

forms

Description

I have created few custom input components which are basically wrappers around other controls, and they could use validators like [min], [max], ... but I noticed that the selectors for MaxValidator are input[type=number][max][formControlName],input[type=number][max][formControl],input[type=number][max][ngModel] and this prohibits the usage on external components.

Proposed solution

Changing specific selectors to just [max][formControlName],[max][formControl],[max][ngModel] would allow using them everywhere. I have created a custom directive inheriting from the original directive and it works straight out of the box.

Alternatives considered

None

[pkozlowski-opensource]

This is an interesting case. Currently the presence of the input in the directive selector makes sense since we've got a host binding to the max attribute - assuming that such attribute exists on a given element. We can't guarantee it in general.

Having said this other existing validator directives don't have the input restrictions and still bind to attributes that might not exists. So at least we've got inconsistency in our implementation.

[pkozlowski-opensource]

Changing a selector to drop input is a potentially breaking change since the validator directives could start matching in places where they were not before. We need to better understand how real this problem is.

[angular-robot]

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[angular-robot]

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[JeanMeche]

The solution for this is likely what #56226 proposes: allow to use the Validator directives as host directives.