You can now load external Scene files using the new load.sceneFile method. This allows you to dynamically load a Scene into the Scene Manager of your game, and swap to it at will.

src/loader/filetypes/SceneFile.js

@@ -0,0 +1,221 @@
+/**
+ * @author       Richard Davey <rich@photonstorm.com>
+ * @copyright    2018 Photon Storm Ltd.
+ * @license      {@link https://github.com/photonstorm/phaser/blob/master/license.txt|MIT License}
+ */
+
+var Class = require('../../utils/Class');
+var CONST = require('../const');
+var File = require('../File');
+var FileTypesManager = require('../FileTypesManager');
+var GetFastValue = require('../../utils/object/GetFastValue');
+var IsPlainObject = require('../../utils/object/IsPlainObject');
+
+/**
+ * @typedef {object} Phaser.Loader.FileTypes.SceneFileConfig
+ *
+ * @property {string} key - The key of the file. Must be unique within both the Loader and the Text Cache.
+ * @property {string} [url] - The absolute or relative URL to load the file from.
+ * @property {string} [extension='txt'] - The default file extension to use if no url is provided.
+ * @property {XHRSettingsObject} [xhrSettings] - Extra XHR Settings specifically for this file.
+ */
+
+/**
+ * @classdesc
+ * An external Scene JavaScript File suitable for loading by the Loader.
+ *
+ * These are created when you use the Phaser.Loader.LoaderPlugin#sceneFile method and are not typically created directly.
+ *
+ * For documentation about what all the arguments and configuration options mean please see Phaser.Loader.LoaderPlugin#sceneFile.
+ *
+ * @class SceneFile
+ * @extends Phaser.Loader.File
+ * @memberof Phaser.Loader.FileTypes
+ * @constructor
+ * @since 3.16.0
+ *
+ * @param {Phaser.Loader.LoaderPlugin} loader - A reference to the Loader that is responsible for this file.
+ * @param {(string|Phaser.Loader.FileTypes.SceneFileConfig)} key - The key to use for this file, or a file configuration object.
+ * @param {string} [url] - The absolute or relative URL to load this file from. If undefined or `null` it will be set to `<key>.js`, i.e. if `key` was "alien" then the URL will be "alien.js".
+ * @param {XHRSettingsObject} [xhrSettings] - Extra XHR Settings specifically for this file.
+ */
+var SceneFile = new Class({
+
+    Extends: File,
+
+    initialize:
+
+    function SceneFile (loader, key, url, xhrSettings)
+    {
+        var extension = 'js';
+
+        if (IsPlainObject(key))
+        {
+            var config = key;
+
+            key = GetFastValue(config, 'key');
+            url = GetFastValue(config, 'url');
+            xhrSettings = GetFastValue(config, 'xhrSettings');
+            extension = GetFastValue(config, 'extension', extension);
+        }
+
+        var fileConfig = {
+            type: 'text',
+            cache: loader.cacheManager.text,
+            extension: extension,
+            responseType: 'text',
+            key: key,
+            url: url,
+            xhrSettings: xhrSettings
+        };
+
+        File.call(this, loader, fileConfig);
+    },
+
+    /**
+     * Called automatically by Loader.nextFile.
+     * This method controls what extra work this File does with its loaded data.
+     *
+     * @method Phaser.Loader.FileTypes.SceneFile#onProcess
+     * @since 3.16.0
+     */
+    onProcess: function ()
+    {
+        this.state = CONST.FILE_PROCESSING;
+
+        this.data = this.xhrLoader.responseText;
+
+        this.onProcessComplete();
+    },
+
+    /**
+     * Adds this file to its target cache upon successful loading and processing.
+     *
+     * @method Phaser.Loader.FileTypes.SceneFile#addToCache
+     * @since 3.16.0
+     */
+    addToCache: function ()
+    {
+        var code = this.data.concat('(function(){\n' + 'return new ' + this.key + '();\n' + '}).call(this);');
+
+        this.loader.sceneManager.add(this.key, eval(code));
+
+        this.complete = true;
+    }
+
+});
+
+/**
+ * Adds an external Scene file, or array of Scene files, to the current load queue.
+ *
+ * You can call this method from within your Scene's `preload`, along with any other files you wish to load:
+ *
+ * ```javascript
+ * function preload ()
+ * {
+ *     this.load.sceneFile('Level1', 'src/Level1.js');
+ * }
+ * ```
+ *
+ * The file is **not** loaded right away. It is added to a queue ready to be loaded either when the loader starts,
+ * or if it's already running, when the next free load slot becomes available. This happens automatically if you
+ * are calling this from within the Scene's `preload` method, or a related callback. Because the file is queued
+ * it means you cannot use the file immediately after calling this method, but must wait for the file to complete.
+ * The typical flow for a Phaser Scene is that you load assets in the Scene's `preload` method and then when the
+ * Scene's `create` method is called you are guaranteed that all of those assets are ready for use and have been
+ * loaded.
+ *
+ * The key must be a unique String. It is used to add the file to the global Scene Manager upon a successful load.
+ * 
+ * For a Scene File it's vitally important that the key matches the class name in the JavaScript file.
+ * 
+ * For example here is the source file:
+ * 
+ * ```javascript
+ * class ExternalScene extends Phaser.Scene {
+ * 
+ *     constructor ()
+ *     {
+ *         super('myScene');
+ *     }
+ * 
+ * }
+ * ```
+ * 
+ * Because the class is called `ExternalScene` that is the exact same key you must use when loading it:
+ * 
+ * ```javascript
+ * function preload ()
+ * {
+ *     this.load.sceneFile('ExternalScene', 'src/yourScene.js');
+ * }
+ * ```
+ * 
+ * The key that is used within the Scene Manager can either be set to the same, or you can override it in the Scene
+ * constructor, as we've done in the example above, where the Scene key was changed to `myScene`.
+ * 
+ * The key should be unique both in terms of files being loaded and Scenes already present in the Scene Manager.
+ * Loading a file using a key that is already taken will result in a warning. If you wish to replace an existing file
+ * then remove it from the Scene Manager first, before loading a new one.
+ *
+ * Instead of passing arguments you can pass a configuration object, such as:
+ *
+ * ```javascript
+ * this.load.sceneFile({
+ *     key: 'Level1',
+ *     url: 'src/Level1.js'
+ * });
+ * ```
+ *
+ * See the documentation for `Phaser.Loader.FileTypes.SceneFileConfig` for more details.
+ *
+ * Once the file has finished loading it will be added to the Scene Manager.
+ *
+ * ```javascript
+ * this.load.sceneFile('Level1', 'src/Level1.js');
+ * // and later in your game ...
+ * this.scene.start('Level1');
+ * ```
+ *
+ * If you have specified a prefix in the loader, via `Loader.setPrefix` then this value will be prepended to this files
+ * key. For example, if the prefix was `WORLD1.` and the key was `Story` the final key will be `WORLD1.Story` and
+ * this is what you would use to retrieve the text from the Scene Manager.
+ *
+ * The URL can be relative or absolute. If the URL is relative the `Loader.baseURL` and `Loader.path` values will be prepended to it.
+ *
+ * If the URL isn't specified the Loader will take the key and create a filename from that. For example if the key is "story"
+ * and no URL is given then the Loader will set the URL to be "story.js". It will always add `.js` as the extension, although
+ * this can be overridden if using an object instead of method arguments. If you do not desire this action then provide a URL.
+ *
+ * Note: The ability to load this type of file will only be available if the Scene File type has been built into Phaser.
+ * It is available in the default build but can be excluded from custom builds.
+ *
+ * @method Phaser.Loader.LoaderPlugin#sceneFile
+ * @fires Phaser.Loader.LoaderPlugin#addFileEvent
+ * @since 3.16.0
+ *
+ * @param {(string|Phaser.Loader.FileTypes.SceneFileConfig|Phaser.Loader.FileTypes.SceneFileConfig[])} key - The key to use for this file, or a file configuration object, or array of them.
+ * @param {string} [url] - The absolute or relative URL to load this file from. If undefined or `null` it will be set to `<key>.js`, i.e. if `key` was "alien" then the URL will be "alien.js".
+ * @param {XHRSettingsObject} [xhrSettings] - An XHR Settings configuration object. Used in replacement of the Loaders default XHR Settings.
+ *
+ * @return {Phaser.Loader.LoaderPlugin} The Loader instance.
+ */
+FileTypesManager.register('sceneFile', function (key, url, xhrSettings)
+{
+    if (Array.isArray(key))
+    {
+        for (var i = 0; i < key.length; i++)
+        {
+            //  If it's an array it has to be an array of Objects, so we get everything out of the 'key' object
+            this.addFile(new SceneFile(this, key[i]));
+        }
+    }
+    else
+    {
+        this.addFile(new SceneFile(this, key, url, xhrSettings));
+    }
+
+    return this;
+});
+
+module.exports = SceneFile;

src/loader/filetypes/index.js

@@ -26,6 +26,7 @@ module.exports = {
     MultiAtlasFile: require('./MultiAtlasFile'),
     PackFile: require('./PackFile'),
     PluginFile: require('./PluginFile'),
+    SceneFile: require('./SceneFile'),
     ScenePluginFile: require('./ScenePluginFile'),
     ScriptFile: require('./ScriptFile'),
     SpriteSheetFile: require('./SpriteSheetFile'),