bug(forms) Async-Validators not triggered for ControlGroup as long as Sync-Errors persist

[choeller]

Steps to reproduce and a minimal demo of the problem

Having a dependent validation in the form "If state is not "BACKLOG" assignee is required" using asyncValidators is not triggering as long as other Validations-Errors (e.g. required on another field) persist.

See the following plnkr:

http://plnkr.co/edit/8bmXDkmKiILUtKkRKhaf?p=preview

When your first action is to choose the state, the asncValidator will not be executed! Only after making the title field valid, by typing something in the title-field async-Validation works.

Current behavior

Async-Validations only get triggered, when no invalid sync-validations are present.

Expected/desired behavior

Async-Validations should be triggered independent of other validation errors.

Other information

[pkozlowski-opensource]

This is by design and we've got a test to prove it:

angular/modules/@angular/forms/test/form_control_spec.ts

Lines 177 to 187 in e42a057

	it('should run the async validator only when the sync validator passes', fakeAsync(() => {
	const c = new FormControl('', Validators.required, asyncValidator('expected'));
	tick();
	expect(c.errors).toEqual({'required': true});
	c.setValue('some value');
	tick();
	expect(c.errors).toEqual({'async': true});
	}));

I guess that the reasoning is that async validation is "expensive" and as such should run after sync validators.

Async-Validations should be triggered independent of other validation errors.

Why? If sync validators mark a filed as invalid there is no point in checking with async validators. It was already market as invalid.

Do you have a specific use-case where the current design causes problems?

[kara]

Yep, this is by design.

[angular-automatic-lock-bot]

This issue has been automatically locked due to inactivity.
Please file a new issue if you are encountering a similar or related problem.

Read more about our automatic conversation locking policy.

_{This action has been performed automatically by a bot.}