Angular 4 remove required validator conditionally

I don't like clearing and setting validators, as I have to repeat all static validators (patterns, min, max, etc.) just to have a dynamic "required" validator.

I use a conditional validator:

export function conditionalValidator(condFn: (control: AbstractControl) => boolean,
validators: ValidatorFn | ValidatorFn[]): ValidatorFn {
  return (control) => {
    if (!condFn(control)) {
      return null;
    }

    if (!Array.isArray(validators)) {
      return validators(control);
    }

    return validators.map(v => v(control)).reduce((errors, result) =>
      result === null ? errors :
        (Object.assign(errors || {}, result))
    );
  };
}

I can then mix a static validator with a dynamic "required" condition:

this.fb.group({name: ['', [Validators.minLength(4),
                 conditionalValidator(this.isClientProj, Validators.required)]]}

Where isClientProj() is the condition function (closure)

we can use setValidators to remove validation.

setValidators(newValidator: ValidatorFn | ValidatorFn[]): void

setValidators() - setValidators programmatically adds the sync validators. This method will remove all the previously added sync or async validators.

this.form.get('title').setValidators(null); 
this.form.get('title').setErrors(null); 

You can use: AbstractControl.removeValidators(validator: ValidatorFn)

Not sure if it is possible in angular 4, but definately in Angular 12 and higher.

It needs however, a reference to the exact same function. Just giving it Validators.required does not work. You need to create a unique reference to it:

requiredValidator = Validators.required;
   
this.form = this._fb.group({
    title: ['', [this.requiredValidator, Validators.minLength(3), Validators.maxLength(50)]],
    description: ['', [this.requiredValidator, Validators.minLength(3)]]
}); 

saveDraft() {
    this.title.removeValidators(this.requiredValidator); 
}

get title(): AbstractControl {
    return this.form.get('title');
}

To Add Validators:

this.form = this._fb.group({
    title: ['', [Validators.required, Validators.minLength(3), Validators.maxLength(50)]],
    description: ['', [Validators.required, Validators.minLength(3)]]
});

or

this.form.get('title').setValidators([Validators.required,Validators.minLength(3), Validators.maxLength(50)]);

To Remove the 'Required' validator only, you can reset the validators.

saveDraft() {
     this.form.get('title').setValidators([Validators.minLength(3), Validators.maxLength(50)]);
     this.form.get('title').updateValueAndValidity();
}

updateValueAndValidity determines how the control propagates changes and emits events when the value and validators are changed

Unfortunately Angular doesn't have a removeValidator capability at this point in time. All you can do is re-set the validators without the one you want to remove, so you need to know which validators you want to keep rather than which one you want to remove. so this:

this.form.get('title').setValidators([Validators.minLength(3), Validators.maxLength(50)]);

Is the closest you have to a remove function. You can't access the current validators on a formcontrol either to try and write your own remove function. The best you could do is write your own form control validation manager class that can keep track of the validators on a given control and manage them for you.

I had the same problem with saving entry as draft and prepared the following solution:

@Component({
    // ...
})
export class FormComponent{
    form: FormGroup;

    constructor(private fb: FormBuilder){
        this.form = this.fb.group({
            name: ['', Validators.required, Validators.maxLength(20)],
            description: ['', Validators.required, Validators.maxLength(200)],
            address: this.fb.group({
                line1: ['', Validators.required, Validators.maxLength(100)],
                line2: ['', Validators.maxLength(100)]
            })
        });
    }    

    validateDraft(formElement: FormGroup | FormArray | FormControl): boolean {
        let result = true;

        Object.keys(formElement.controls).forEach(field => {
            const control = formElement.get(field);

            if(control instanceof FormControl) {
                control.markAsTouched({ onlySelf: true });

                if(control.errors && control.errors['required']) {
                    control.markAsUntouched({ onlySelf: true });
                }
                else if(control.invalid) {
                    result = false;
                }
            } else if (control instanceof FormArray) {
                if (!this.validateDraft(control)) {
                    result = false;
                } 
            }else if (control instanceof FormGroup) {
                if (!this.validateDraft(control)) {
                    result = false;
                }   
            }
        });
    }

    saveDraft(){
        if(this.validateDraft(this.form)){
            //save draft - ignore required errors
        }
    }

    save(){
        if(this.form.valid){
            //save
        }
    }
}

this.fromName.get("formControlName").setValidators([Validators.required]);//setting validation
this.fromName.get("formControlName").setErrors({'required':true});//error message
this.fromName.updateValueAndValidity();//update validation


this.fromName.get("formControlName").clearValidators([Validators.required]);//clear validation
this.fromName.get("formControlName").setErrors(null);//updating error message
this.fromName.updateValueAndValidity();//update validation

Use empty array to remove all existing validators.

this.frmFeasibility.controls['pop_name'].setValidators([]);
this.frmFeasibility.controls['pop_name'].updateValueAndValidity();

you can use this to clear validation from reactive form

this.form.controls['title'].clearValidators(); this.form.controls['title'].updateValueAndValidity();

you can use this to add validation in reactive form

this.form.controls['title'].setValidators([Validators.required]); this.form.controls['title'].updateValueAndValidity();