title: Angular - set value on formControl without resetting errors
body: <p>I have the following problem with Angular 6:</p>
  
  <p>I'm trying to manually set the errors property on a formControl with <code>.setErrors()</code> and setting the value with <code>.setValue()</code> afterwards. The setValue method. To my detriment, <code>.setValue()</code> re-runs the validation and resets the <code>errors</code> property on the formControl to <code>null</code>. Like so:</p>
  
  <pre><code>import { OnInit} from '@angular/core';
  import { FormControl} from '@angular/forms';
  
  export class CustomComponent implements OnInit {
    formControl: FormControl;
  
    ngOnInit() {
      this.formControl = new FormControl();
      this.formControl.setErrors({required: true});
      this.formControl.setValue('foo'); // resets formControl.errors to null
      console.log(this.formControl.errors); // returns null
    }
  
  }
  </code></pre>
  
  <p>Any ideas?</p>