Why does adding additional AngularJS validation directives cause $asyncValidators to run multiple times?

Question

Why does adding additional AngularJS validation directives cause $asyncValidators to run multiple times on page load?

I created a custom directive which

Answer 1

I followed @New Dev's advice and implemented a simple caching routine which fulfilled my requirement quite nicely, here's what I came up with ..

link: function (scope, element, attributes, ngModel) {

        var cache = {};
        ngModel.$asyncValidators.validateValue = function (modelValue) {
            if (modelValue && cache[modelValue] !== true) {
                return MyHttpService.validateValue(modelValue).then(function (resolved) {
                    cache[modelValue] = true; // cache 
                    return resolved;
                }, function(rejected) {
                    cache[modelValue] = false;
                    return $q.reject(rejected);
                });
            } else {
                return $q.resolve("OK");
            }
        };
    }