Angular get all errors from FormGroup, flatten

utils.ts

import {
  AbstractControl,
  FormArray,
  FormGroup,
  ValidationErrors
} from '@angular/forms';

function parseControlError(
  key: string,
  control: AbstractControl
): Record<string, ValidationErrors> {
  const res: Record<string, ValidationErrors> = {};

  if (control instanceof FormGroup || control instanceof FormArray) {
    const errors = getAllFormErrors(control, key);
    if (Object.keys(errors).length > 0) {
      Object.assign(res, errors);
    }
  } else if (control.errors) {
    res[key] = control.errors;
  }

  return res;
}

export function getAllFormErrors(
  form: FormGroup | FormArray,
  path = ''
): Record<string, ValidationErrors> {
  const res: Record<string, ValidationErrors> = {};

  if (form instanceof FormGroup) {
    for (const key of Object.keys(form.controls)) {
      Object.assign(
        res,
        parseControlError(
          `${path ? `${path}.${key}` : key}`,
          form.controls[key]
        )
      );
    }
  }

  if (form instanceof FormArray) {
    for (let i = 0; i < form.controls.length; i++) {
      Object.assign(
        res,
        parseControlError(`${path ? `${path}.${i}` : i}`, form.controls[i])
      );
    }
  }

  return res;
}