fix(forms): fix Validators.min/maxLength with FormArray (#13095)

Fixes #13089

modules/@angular/forms/src/model.ts

@@ -36,10 +36,6 @@ export const PENDING = 'PENDING';
  */
 export const DISABLED = 'DISABLED';
 
-export function isControl(control: Object): boolean {
-  return control instanceof AbstractControl;
-}
-
 function _find(control: AbstractControl, path: Array<string|number>| string, delimiter: string) {
   if (path == null) return null;
 

modules/@angular/forms/src/validators.ts

@@ -72,7 +72,7 @@ export class Validators {
       if (isEmptyInputValue(control.value)) {
         return null;  // don't validate empty values to allow optional controls
       }
-      const length = typeof control.value === 'string' ? control.value.length : 0;
+      const length: number = control.value ? control.value.length : 0;
       return length < minLength ?
           {'minlength': {'requiredLength': minLength, 'actualLength': length}} :
           null;
@@ -84,7 +84,7 @@ export class Validators {
    */
   static maxLength(maxLength: number): ValidatorFn {
     return (control: AbstractControl): {[key: string]: any} => {
-      const length = typeof control.value === 'string' ? control.value.length : 0;
+      const length: number = control.value ? control.value.length : 0;
       return length > maxLength ?
           {'maxlength': {'requiredLength': maxLength, 'actualLength': length}} :
           null;

modules/@angular/forms/test/validators_spec.ts

@@ -8,7 +8,7 @@
 
 import {fakeAsync, tick} from '@angular/core/testing';
 import {describe, expect, it} from '@angular/core/testing/testing_internal';
-import {AbstractControl, FormControl, Validators} from '@angular/forms';
+import {AbstractControl, FormArray, FormControl, Validators} from '@angular/forms';
 import {Observable} from 'rxjs/Observable';
 
 import {normalizeAsyncValidator} from '../src/directives/normalize_validator';
@@ -68,6 +68,18 @@ export function main() {
           'minlength': {'requiredLength': 2, 'actualLength': 1}
         });
       });
+
+      it('should not error when FormArray has valid length', () => {
+        const fa = new FormArray([new FormControl(''), new FormControl('')]);
+        expect(Validators.minLength(2)(fa)).toBeNull();
+      });
+
+      it('should error when FormArray has invalid length', () => {
+        const fa = new FormArray([new FormControl('')]);
+        expect(Validators.minLength(2)(fa)).toEqual({
+          'minlength': {'requiredLength': 2, 'actualLength': 1}
+        });
+      });
     });
 
     describe('maxLength', () => {
@@ -85,6 +97,18 @@ export function main() {
           'maxlength': {'requiredLength': 2, 'actualLength': 3}
         });
       });
+
+      it('should not error when FormArray has valid length', () => {
+        const fa = new FormArray([new FormControl(''), new FormControl('')]);
+        expect(Validators.maxLength(2)(fa)).toBeNull();
+      });
+
+      it('should error when FormArray has invalid length', () => {
+        const fa = new FormArray([new FormControl(''), new FormControl('')]);
+        expect(Validators.maxLength(1)(fa)).toEqual({
+          'maxlength': {'requiredLength': 1, 'actualLength': 2}
+        });
+      });
     });
 
     describe('pattern', () => {