fix(input): create max and/or min validation whatever the initial value is

- fix issue angular#10307
- change tests to corresponding changes
- also change tests for ngmax and ngmin (though they have no some issue)

Closes angular#10307

Author: tobyee

src/ng/directive/input.js

@@ -1230,7 +1230,7 @@ function numberInputType(scope, element, attr, ctrl, $sniffer, $browser) {
     return value;
   });
 
-  if (attr.min || attr.ngMin) {
+  if (isDefined(attr.min) || attr.ngMin) {
     var minVal;
     ctrl.$validators.min = function(value) {
       return ctrl.$isEmpty(value) || isUndefined(minVal) || value >= minVal;
@@ -1246,7 +1246,7 @@ function numberInputType(scope, element, attr, ctrl, $sniffer, $browser) {
     });
   }
 
-  if (attr.max || attr.ngMax) {
+  if (isDefined(attr.max) || attr.ngMax) {
     var maxVal;
     ctrl.$validators.max = function(value) {
       return ctrl.$isEmpty(value) || isUndefined(maxVal) || value <= maxVal;

test/ng/directive/inputSpec.js

@@ -4161,10 +4161,14 @@ describe('input', function() {
       });
 
       it('should validate even if min value changes on-the-fly', function() {
-        scope.min = 10;
+        scope.min = undefined;
         compileInput('<input type="number" ng-model="value" name="alias" min="{{min}}" />');
+        expect(inputElm).toBeValid();
 
         changeInputValueTo('15');
+
+        scope.min = 10;
+        scope.$digest();
         expect(inputElm).toBeValid();
 
         scope.min = 20;
@@ -4202,10 +4206,14 @@ describe('input', function() {
       });
 
       it('should validate even if the ngMin value changes on-the-fly', function() {
-        scope.min = 10;
+        scope.min = undefined;
         compileInput('<input type="number" ng-model="value" name="alias" ng-min="min" />');
+        expect(inputElm).toBeValid();
 
         changeInputValueTo('15');
+
+        scope.min = 10;
+        scope.$digest();
         expect(inputElm).toBeValid();
 
         scope.min = 20;
@@ -4244,10 +4252,14 @@ describe('input', function() {
       });
 
       it('should validate even if max value changes on-the-fly', function() {
-        scope.max = 10;
+        scope.max = undefined;
         compileInput('<input type="number" ng-model="value" name="alias" max="{{max}}" />');
+        expect(inputElm).toBeValid();
 
         changeInputValueTo('5');
+
+        scope.max = 10;
+        scope.$digest();
         expect(inputElm).toBeValid();
 
         scope.max = 0;
@@ -4285,10 +4297,14 @@ describe('input', function() {
       });
 
       it('should validate even if the ngMax value changes on-the-fly', function() {
-        scope.max = 10;
+        scope.max = undefined;
         compileInput('<input type="number" ng-model="value" name="alias" ng-max="max" />');
+        expect(inputElm).toBeValid();
 
         changeInputValueTo('5');
+
+        scope.max = 10;
+        scope.$digest();
         expect(inputElm).toBeValid();
 
         scope.max = 0;