Angular Material: Reseting reactiveform shows validation error

Question

I am using angular5 reactivemodule to show a form in my application. I had also used required validator which will subsequently make the field in red color and show an error msg to the user.

It is working as expected but when I reset the form using

this.form.reset()

the form shows me a validation error that the specific field is required. I also used form.markAsPristine() or form.markAsUntouched() to make it work but the problem persist after applying multiple combination of possible pairs.

example.html

<form [formGroup]="checkForm" (ngSubmit)="submitForm()">
  <mat-form-field>
    <input matInput formControlName="name" placeholder="name" />
    <mat-error *ngIf="checkForm.get('name').errors?.required">
      Name is required.
    </mat-error>
  </mat-form-field>
  <mat-form-field>
    <input matInput formControlName="email" placeholder="email" />
    <mat-error *ngIf="checkForm.get('email').errors?.required">
      Name is required.
    </mat-error>
  </mat-form-field>
  <button [disabled]="checkForm.invalid" type="submit">add</button>
</form>

example.ts

checkForm  = this.formBuilder.group({
  'name': ['', Validators.required],
  'email': ['', Validators.required]
});

submitForm() {
   this.checkForm.reset();
   // this.checkForm.markAsPristine();
   this.checkForm.markAsUntouched();      
}

Any help is appreciated.

Answer 1

By default, Angular/Material watch formControl's error state not only by touched but also submitted status of the form, see below source code.

isErrorState(control: FormControl | null, form: FormGroupDirective | NgForm | null): boolean {
  return !!(control && control.invalid && (control.touched || (form && form.submitted)));
                                                                       ^^^^^^^^^^^^^^
}

For reason above, you also need to reset the form to unsubmitted status.

---

You can call resetForm of FormGroupDirective(getting instance by ViewChild) for it will reset both the form data and submit status.

<form #form="ngForm" [formGroup]="checkForm" (ngSubmit)="submitForm(form)">
  ...
</form>

@ViewChild('form') form;

submitForm() {
  this.form.resetForm();
  ...
}

---

You can also overwrite the default one via implementing ErrorStateMatcher with custom conditions such as ignore submitted status of the form, and apply it on material components.

<mat-form-field>
  <input matInput formControlName="name" placeholder="name" [errorStateMatcher]="errorMatcher" />
  <mat-error *ngIf="checkForm.get('name').errors?.required">
    Name is required.
  </mat-error>
</mat-form-field>

// define custom ErrorStateMatcher
export class CustomErrorStateMatcher implements ErrorStateMatcher {
  isErrorState(control: FormControl, form: NgForm | FormGroupDirective | null) {
    return control && control.invalid && control.touched;
  }
}

// component code
@Component({...})
export class CustomComponent {
  // create instance of custom ErrorStateMatcher
  errorMatcher = new CustomErrorStateMatcher();
}

---

see fixed demo.