fix(input): ngMinlength/ngMaxlength should not invalidate non-stringlike values

A regression reported in angular#5936 shows that prior to cdc4d48, an
input with an ngMinlength or ngMaxlength validator would not invalidate values where value.length
was undefined.

The behaviour of this validator is still incorrect in the case of objects with a length property
which are not arrays or strings, and will most likely remain that way. This cannot change as it is
possibly desirable to use ngMinlength/ngMaxlength in conjunction with ngList.

Closes angular#5936
Closes angular#6000

Author: caitp

src/ng/directive/input.js

@@ -998,7 +998,8 @@ function textInputType(scope, element, attr, ctrl, $sniffer, $browser) {
   if (attr.ngMinlength) {
     var minlength = int(attr.ngMinlength);
     var minLengthValidator = function(value) {
-      return validate(ctrl, 'minlength', ctrl.$isEmpty(value) || value.length >= minlength, value);
+      return validate(ctrl, 'minlength', ctrl.$isEmpty(value) ||
+        (!isDefined(value.length) || value.length >= minlength), value);
     };
 
     ctrl.$parsers.push(minLengthValidator);
@@ -1009,7 +1010,8 @@ function textInputType(scope, element, attr, ctrl, $sniffer, $browser) {
   if (attr.ngMaxlength) {
     var maxlength = int(attr.ngMaxlength);
     var maxLengthValidator = function(value) {
-      return validate(ctrl, 'maxlength', ctrl.$isEmpty(value) || value.length <= maxlength, value);
+      return validate(ctrl, 'maxlength', ctrl.$isEmpty(value) ||
+        (!isDefined(value.length) || value.length <= maxlength), value);
     };
 
     ctrl.$parsers.push(maxLengthValidator);

test/ng/directive/inputSpec.js

@@ -744,6 +744,34 @@ describe('input', function() {
       changeInputValueTo('aaa');
       expect(scope.value).toBe('aaa');
     });
+
+
+    it('should invalidate model values shorter than given minlength', function() {
+      compileInput('<input type="text" ng-model="value" ng-minlength="5" />');
+
+      scope.$apply(function() {
+        scope.value = "1234";
+      });
+
+      expect(inputElm).toBeInvalid();
+
+      scope.$apply(function() {
+        scope.value = "123456789";
+      });
+
+      expect(inputElm).toBeValid();
+    });
+
+
+    it('should not invalidate model-values which are not string-like or array-like', function() {
+      compileInput('<input type="text" ng-model="value" ng-minlength="3" />');
+
+      scope.$apply(function() {
+        scope.value = 10;
+      });
+
+      expect(inputElm).toBeValid();
+    });
   });
 
 
@@ -758,6 +786,34 @@ describe('input', function() {
       changeInputValueTo('aaa');
       expect(scope.value).toBe('aaa');
     });
+
+
+    it('should invalidate model values longer than given maxlength', function() {
+      compileInput('<input type="text" ng-model="value" ng-maxlength="5" />');
+
+      scope.$apply(function() {
+        scope.value = "123456789";
+      });
+
+      expect(inputElm).toBeInvalid();
+
+      scope.$apply(function() {
+        scope.value = "1234";
+      });
+
+      expect(inputElm).toBeValid();
+    });
+
+
+    it('should not invalidate model-values which are not string-like or array-like', function() {
+      compileInput('<input type="text" ng-model="value" ng-maxlength="3" />');
+
+      scope.$apply(function() {
+        scope.value = 1000;
+      });
+
+      expect(inputElm).toBeValid();
+    });
   });