statusChanges is not fired upon dynamic validation added with NG_VALIDATOR

🐞 bug report

Affected Package

The issue is caused by package @angular/forms

Is this a regression?

Probably not

Description

You can create directives that provide NG_VALIDATOR token so additional validation can be applied. Simple case, I have a checkbox that hides a particular field. If the field is enabled, I want it to be required. I can do this with built-in required directive. When I toggle my field, form becomes invalid because it is empty and required. However statusChanges stream does not fire to let me know that form became INVALID

🔬 Minimal Reproduction

https://stackblitz.com/edit/angular-ng-validator-bug

🌍 Your Environment

Angular Version:

10.0.1

Anything else relevant? Watch out for ExpressionChanged error, form does actually become invalid the moment directive with NG_VALIDATOR is instantiated but the binding does not update. That’s how I actually got to use statusChanges stream and noticed it’s not firing.

[waterplea]

Got it, thanks for the quick reply. In case it’s helpful, here’s the actual case where I ran into this: https://stackblitz.com/edit/angular-declarative-dynamic-validation?file=src%2Fapp%2Fvalidator%2Fvalidator.directive.ts&s=09

I was investigating declarative approaches to dynamic validation, as opposed to imperative setValidators calls. Since it’s dynamic I had to call validation manually anyway, so it’s not blocking, but still rather strange behaviour.

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