AngularJS 1.4+ Styleguide-friendly support of ngModel in input[type=file] elements

input-file.decorator.js

(function() {
    'use strict';

    /**
     * @ngdoc input
     * @name input[file]
     *
     * @description
     * Adds very basic support for ngModel to `input[type=file]` fields.
     *
     * Requires AngularJS 1.4.x or later. Does not support Internet Explorer 9 - the browser's
     * implementation of `HTMLInputElement` must have a `files` property for file inputs.
     *
     * @param {string} ngModel
     *  Assignable AngularJS expression to data-bind to. The data-bound object will be an instance
     *  of {@link https://developer.mozilla.org/en-US/docs/Web/API/FileList `FileList`}.
     * @param {string=} name Property name of the form under which the control is published.
     * @param {string=} ngChange
     *  AngularJS expression to be executed when input changes due to user interaction with the
     *  input element.
     */
    angular
        .module('yourModuleNameHere')
        .decorator('inputDirective', scpInputFileDecorator);

    scpInputFileDecorator.$inject = ['$delegate', '$browser', '$sniffer', '$filter', '$parse'];
    function scpInputFileDecorator($delegate, $browser, $sniffer, $filter, $parse) {
        var inputDirective = $delegate[0],
            preLink = inputDirective.link.pre;

        inputDirective.link.pre = function (scope, element, attr, ctrl) {
            if (ctrl[0]) {
                if (angular.lowercase(attr.type) === 'file') {
                    fileInputType(
                        scope, element, attr, ctrl[0], $sniffer, $browser, $filter, $parse);
                } else {
                    preLink.apply(this, arguments);
                }
            }
        };

        return $delegate;
    }

    function fileInputType(scope, element, attr, ctrl, $sniffer, $browser, $filter, $parse) {
        element.on('change', function (ev) {
            if (angular.isDefined(element[0].files)) {
                ctrl.$setViewValue(element[0].files, ev && ev.type);
            }
        })

        ctrl.$isEmpty = function (value) {
            return !value || value.length === 0;
        };
    }
})();