Enable the asset-manifest to be present in SSR environments

README.md

@@ -58,6 +58,19 @@ var app = new EmberApp(defaults, {
 });
 ```
 
+## Usage with FastBoot / Server-Side Rendering Solutions
+
+Using lazily loaded assets with a server-side rendering solution, such as FastBoot, is often desirable to maximize
+performance for your consumers. However, lazy loading assets on your server is not the same as on the client and
+can actually have negative performance impact. Due to that, the recommendation is to pre-load all your assets in the
+server.
+
+Additionally, at build time we will generate a `node-asset-manifest` file that should be included in your SSR
+environment to ensure that your application can correctly access asset information.
+
+See the ["How to handle running in Node"](https://github.com/trentmwillis/ember-asset-loader/issues/21) issue for more
+information.
+
 ## Pre-loading Assets During Testing
 
 For test environments it is often useful to load all of the assets in a manifest upfront. You can do this by using the

app/asset-manifest.js

@@ -1,13 +1,23 @@
 import environment from './config/environment';
 
-const metaName = environment.modulePrefix + '/asset-manifest';
+const modulePrefix = environment.modulePrefix;
+const metaName = `${modulePrefix}/asset-manifest`;
+const nodeName = `${modulePrefix}/node-asset-manifest`;
+
 let config = {};
 
 try {
-  const rawConfig = document.querySelector('meta[name="' + metaName + '"]').getAttribute('content');
-  config = JSON.parse(unescape(rawConfig));
+  // If we have a Node version of the asset manifest, use that for FastBoot and
+  // similar environments.
+  if (require.has(nodeName)) {
+    config = require(nodeName).default; // eslint-disable-line
+  } else {
+    const rawConfig = document.querySelector('meta[name="' + metaName + '"]').getAttribute('content');
+    config = JSON.parse(unescape(rawConfig));
+  }
 } catch(err) {
-  throw new Error('Could not read asset manifest from meta tag with name "' + metaName + '".');
+  throw new Error('Failed to load asset manifest. For browser environments, verify the meta tag with name "'+ metaName +
+    '" is present. For non-browser environments, verify that you included the node-asset-manifest module.');
 }
 
 export default config;

lib/generate-asset-manifest.js

@@ -1,6 +1,7 @@
 var Funnel = require('broccoli-funnel');
 var mergeTrees = require('broccoli-merge-trees');
 var AssetManifestGenerator = require('./asset-manifest-generator');
+var NodeAssetManifestGenerator = require('./node-asset-manifest-generator');
 
 /**
  * Given a tree, this function will generate an asset manifest and merge it back
@@ -22,6 +23,7 @@ module.exports = function generateAssetManifest(tree, options) {
 
   var bundlesLocation = options.bundlesLocation || 'bundles';
   var supportedTypes = options.supportedTypes;
+  var appName = options.appName;
 
   // Get all the bundles for this application
   var bundles = new Funnel(tree, {
@@ -42,8 +44,14 @@ module.exports = function generateAssetManifest(tree, options) {
     annotation: 'Asset Manifest Generator'
   });
 
+  // Generate a module that can be used in Node environments
+  var nodeManifest = new NodeAssetManifestGenerator(manifest, {
+    appName: appName,
+    annotation: 'Node Asset Manifest Generator'
+  });
+
   // Merge the manifest back into the build
-  return mergeTrees([ tree, manifest ], {
+  return mergeTrees([ tree, manifest, nodeManifest ], {
     annotation: 'Merge Asset Manifest',
     overwrite: true
   });

lib/manifest-generator.js

@@ -2,6 +2,7 @@ var path = require('path');
 var fs = require('fs-extra');
 var Addon = require('ember-cli/lib/models/addon');
 var mergeTrees = require('broccoli-merge-trees');
+var objectAssign = require('object-assign');
 var findHost = require('./utils/find-host');
 
 /**
@@ -40,8 +41,10 @@ var ManifestGenerator = Addon.extend({
       return tree;
     }
 
+    var manifestOptions = objectAssign({ appName: app.name }, this.manifestOptions);
+
     var generateAssetManifest = require('./generate-asset-manifest'); // eslint-disable-line global-require
-    var treeWithManifest = generateAssetManifest(tree, this.manifestOptions);
+    var treeWithManifest = generateAssetManifest(tree, manifestOptions);
 
     var indexName = options.outputPaths.app.html;
     var insertAssetManifest = require('./insert-asset-manifest'); // eslint-disable-line global-require

lib/node-asset-manifest-generator.js

@@ -0,0 +1,48 @@
+var Plugin = require('broccoli-caching-writer');
+var walk = require('walk-sync');
+var path = require('path');
+var fs = require('fs-extra');
+
+/**
+ * A Broccoli plugin to generate a module to be used in Node for resolving the
+ * asset manifest. Primary use case is for FastBoot like environments.
+ *
+ * @class NodeAssetManifestGenerator
+ * @extends BroccoliCachingWriter
+ */
+function NodeAssetManifestGenerator(inputTrees, options) {
+  options = options || {};
+
+  this.appName = options.appName;
+
+  Plugin.call(this, [ inputTrees ], {
+    annotation: options.annotation
+  });
+}
+
+NodeAssetManifestGenerator.prototype = Object.create(Plugin.prototype);
+NodeAssetManifestGenerator.prototype.constructor = NodeAssetManifestGenerator;
+
+/**
+ * Generates an asset manifest module on build from the passed in
+ * asset-manifest.json file.
+ */
+NodeAssetManifestGenerator.prototype.build = function() {
+  var inputPath = this.inputPaths[0];
+  var assetManifestPath = path.join(inputPath, 'asset-manifest.json');
+  var assetManifest = fs.readJsonSync(assetManifestPath);
+
+  var moduleTemplatePath = path.join(__dirname, './utils/node-module-template.js');
+  var moduleTemplate = fs.readFileSync(moduleTemplatePath, 'utf-8');
+  var module = moduleTemplate
+    .replace('APP_NAME', this.appName)
+    .replace('ASSET_MANIFEST', JSON.stringify(assetManifest));
+
+  var outputAssets = path.join(this.outputPath, 'assets');
+  fs.mkdirSync(outputAssets);
+
+  var nodeModuleFile = path.join(outputAssets, 'node-asset-manifest.js');
+  fs.writeFileSync(nodeModuleFile, module);
+};
+
+module.exports = NodeAssetManifestGenerator;

lib/utils/node-module-template.js

@@ -0,0 +1,6 @@
+/* eslint-disable */
+define('APP_NAME/node-asset-manifest', function() {
+  return {
+    default: ASSET_MANIFEST
+  };
+});

node-tests/generate-asset-manifest-test.js

@@ -20,10 +20,14 @@ describe('generate-asset-manifest', function() {
       var originalFiles = walk(inputTree);
       var outputFiles = walk(output);
 
-      assert.equal(outputFiles.length, originalFiles.length + 1, 'output files has one more file than originally');
+      assert.equal(outputFiles.length, originalFiles.length + 2, 'output files has two more files than originally');
+
       assert.equal(originalFiles.indexOf('asset-manifest.json'), -1, 'original files does not contain an asset manifest');
       assert.notEqual(outputFiles.indexOf('asset-manifest.json'), -1, 'output files does contain an asset manifest');
 
+      assert.equal(originalFiles.indexOf('assets/node-asset-manifest.js'), -1, 'original files does not contain a Node asset manifest module');
+      assert.notEqual(outputFiles.indexOf('assets/node-asset-manifest.js'), -1, 'output files does contain a Node asset manifest module');
+
       var manifestFile = path.join(output, 'asset-manifest.json');
       var manifest = fs.readJsonSync(manifestFile);
       var expectedManifest = fs.readJsonSync(path.join(manifestsPath, manifestName + '.json'));
@@ -55,10 +59,14 @@ describe('generate-asset-manifest', function() {
       var originalFiles = walk(inputTree);
       var outputFiles = walk(output);
 
-      assert.equal(outputFiles.length, originalFiles.length, 'output files has same number of files as originally');
+      assert.equal(outputFiles.length, originalFiles.length + 1, 'output files has one more file than originally');
+
       assert.notEqual(originalFiles.indexOf('asset-manifest.json'), -1, 'original files does contain an asset manifest');
       assert.notEqual(outputFiles.indexOf('asset-manifest.json'), -1, 'output files does contain an asset manifest');
 
+      assert.equal(originalFiles.indexOf('assets/node-asset-manifest.js'), -1, 'original files does not contain a Node asset manifest module');
+      assert.notEqual(outputFiles.indexOf('assets/node-asset-manifest.js'), -1, 'output files does contain a Node asset manifest module');
+
       var manifestFile = path.join(output, 'asset-manifest.json');
       var manifest = fs.readJsonSync(manifestFile);
       var expectedManifest = fs.readJsonSync(path.join(manifestsPath, 'full-plus-existing.json'));

package.json

@@ -56,6 +56,7 @@
     "ember-cli-babel": "^5.1.6",
     "exists-sync": "0.0.3",
     "fs-extra": "^0.30.0",
+    "object-assign": "^4.1.0",
     "walk-sync": "^0.2.7"
   },
   "ember-addon": {

tests/index.html

@@ -23,6 +23,10 @@
 
     <script src="{{rootURL}}testem.js" integrity=""></script>
     <script src="{{rootURL}}assets/vendor.js"></script>
+
+    <!-- The following script is included just to verify it will work in Node -->
+    <script src="{{rootURL}}assets/node-asset-manifest.js"></script>
+
     <script src="{{rootURL}}assets/test-support.js"></script>
     <script src="{{rootURL}}assets/dummy.js"></script>
     <script src="{{rootURL}}assets/tests.js"></script>

tests/unit/asset-manifest-test.js

@@ -0,0 +1,57 @@
+/* global require */
+
+import { module, test } from 'qunit';
+
+module('Unit | asset-manifest', {
+  beforeEach() {
+    resetModules();
+    this.originalNodeModule = require.entries['dummy/node-asset-manifest'];
+  },
+
+  afterEach() {
+    require.entries['dummy/node-asset-manifest'] = this.originalNodeModule;
+    resetModules();
+  }
+});
+
+function resetModules() {
+  require.unsee('dummy/node-asset-manifest');
+  require.unsee('dummy/asset-manifest');
+}
+
+test('node-asset-manifest is generated properly', function(assert) {
+  const nodeManifest = require('dummy/node-asset-manifest').default;
+  delete require.entries['dummy/node-asset-manifest'];
+
+  const manifest = require('dummy/asset-manifest').default;
+
+  assert.notStrictEqual(nodeManifest, manifest);
+  assert.deepEqual(nodeManifest, manifest);
+});
+
+test('loads the node-asset-manifest if present', function(assert) {
+  const replacementModule = {};
+  define('dummy/node-asset-manifest', () => ({ default: replacementModule}));
+
+  assert.strictEqual(require('dummy/asset-manifest').default, replacementModule);
+});
+
+test('loads the manifest from the meta tag if available', function(assert) {
+  delete require.entries['dummy/node-asset-manifest'];
+
+  const meta = document.querySelector('meta[name="dummy/asset-manifest"]');
+  const metaContent = meta.getAttribute('content');
+  meta.setAttribute('content', '{"derp":"herp"}');
+  assert.deepEqual(require('dummy/asset-manifest').default, { derp: 'herp' });
+  meta.setAttribute('content', metaContent);
+});
+
+test('throws an error if unable to load the manifest', function(assert) {
+  delete require.entries['dummy/node-asset-manifest'];
+
+  const meta = document.querySelector('meta[name="dummy/asset-manifest"]');
+  const metaContent = meta.getAttribute('content');
+  meta.setAttribute('content', 'herp');
+  assert.throws(() => assert.deepEqual(require('dummy/asset-manifest').default, {}));
+  meta.setAttribute('content', metaContent);
+});