Calendar not working well together with validators

[sabotup]

Hi,

I've been using Calendar component in an Angular Reactive Form and tried to add some validators to it. It all goes well until you try to validate if the user typed something that is a valid date or just left the input field empty. Calendar only returns null if date is not valid or field is empty, so you cannot distinguish between both cases (in my case, empty field is good, invalid value is not). I inspected the code and there is a property in Calendar named "filled" that should tell you if field has some content or not. That's great, I can use this property to determine if the field is empty, so I can do my validation. Problem comes in the moment you realize that validation code runs before this "filled" property gets updated with current value.

This is the code you have right now according to github:

 onInput(event) {  
        let val = event.target.value;   
        try {
            this.value = this.parseValueFromString(val);
            this.updateUI();
            this._isValid = true;
        } 
        catch(err) {
            //invalid date
            this.value = null;
            this._isValid = false;
        }
        
        this.updateModel();
        this.filled = val != null && val.length;
    }

There you can see that model of the component gets updated before "filled" property gets updated with good value. So in my code I had overridden the method just exchanging last two lines of the method:

onInput(event) {  
        let val = event.target.value;   
        try {
            this.value = this.parseValueFromString(val);
            this.updateUI();
            this._isValid = true;
        } 
        catch(err) {
            //invalid date
            this.value = null;
            this._isValid = false;
        }
        
        this.filled = val != null && val.length;
        this.updateModel();
    }

This way "filled" has the updated value and can be used to validate field is empty. I would prefer to have some method to check status of the field instead of relying directly on the property, but I leave that decision to you.

I will submit a PR with my proposed fix for you to consider.

Also created same issue on the forum:

https://forum.primefaces.org/viewtopic.php?f=35&t=50922

Thanks.