What is the purpose of the new built in 'parse' validation key in Angular 1.3?

Question

The behavior of the ngModelController parsing pipeline seems to have changed between Angular 1.2 and 1.3. I now always see a new validation key named \'parse\'

Answer 1

Angular 1.3 rationalized things to make a clean distinction between parsing and validating.

Parsing

Angular now automatically adds a 'parse' key to all $error collections with its value set accordingly - true if any of the parsers returned undefined, false otherwise.

For an unparsable value (alphas entered for a number, badly formatted date, etc), we should return undefined from the parser. This will cause Angular to remove any $error keys already set, and replace the entire object with just { "parse": true }. No more parsers will be run. The model will not be updated. The $parsers array should now only be used for parsing.

Validation

ngModelController has a new $validators property, to which we can assign validation functions. These will only be run if the parsing pipeline was successful. Return false from one of these functions for a value that is parsable as the required datatype, but merely invalid (string too long, number out of range etc). The name of the validator function becomes the validation key in the $error object. All validators will be run, even if one returns false. The model will only be updated if validation is successful.

This is potentially a breaking change for existing applciations, as people frequently returned undefined from parsers for an invalid value. Here is what I had, which is a typical example:

ctrl.$parsers.push(function (value) {
    if (!angular.isDefined(attrs.minNumber)) {
        return value;
    }
    var valid = angular.isUndefined(value) || Number(value) >= Number(attrs.minNumber);
    ctrl.$setValidity('minNumber', valid);
    return valid ? value : undefined;
});

Under this new scheme, this should be moved to a validation function instead:

ctrl.$validators.minNumber = function (value) {
    return !value || !angular.isDefined(attrs.minNumber) || (value >= Number(attrs.minNumber));
});

Here is the directive with everything fixed up:

angular.module('app', []).directive('number', function () {
    return {
        require: 'ngModel',
        link: function (scope, elem, attrs, ctrl) {

            // valid number
            ctrl.$parsers.push(function (value) {
                if(value === '') return value;
                return isFinite(value) ? Number(value) : undefined;
            });

            ctrl.$validators.minNumber = function (value) {
                return !value || !angular.isDefined(attrs.minNumber) || (value >= Number(attrs.minNumber));
            };

            ctrl.$validators.maxNumber = function (value) {
                return !value || !angular.isDefined(attrs.maxNumber) || (value <= Number(attrs.maxNumber));
            };
        }
    };
});

http://jsfiddle.net/snkesLv4/10/

I really like this new way - it is much cleaner.