HTML bundle loader

src/Bundler.js

@@ -51,6 +51,10 @@ class Bundler extends EventEmitter {
       browser: require.resolve('./builtins/loaders/browser/js-loader'),
       node: require.resolve('./builtins/loaders/node/js-loader')
     });
+    this.addBundleLoader('html', {
+      browser: require.resolve('./builtins/loaders/browser/html-loader'),
+      node: require.resolve('./builtins/loaders/node/html-loader')
+    });
 
     this.pending = false;
     this.loadedAssets = new Map();
@@ -616,6 +620,12 @@ class Bundler extends EventEmitter {
     let isEntryAsset =
       asset.parentBundle && asset.parentBundle.entryAsset === asset;
 
+    // If the asset generated a representation for the parent bundle type, and this
+    // is not an async import, add it to the current bundle
+    if (bundle.type && asset.generated[bundle.type] != null && !dep.dynamic) {
+      bundle.addAsset(asset);
+    }
+
     if ((dep && dep.dynamic) || !bundle.type) {
       // If the asset is already the entry asset of a bundle, don't create a duplicate.
       if (isEntryAsset) {
@@ -624,24 +634,23 @@ class Bundler extends EventEmitter {
 
       // Create a new bundle for dynamic imports
       bundle = bundle.createChildBundle(asset, dep);
-    } else if (asset.type && !this.packagers.has(asset.type)) {
+    } else if (
+      asset.type &&
+      !this.packagers.get(asset.type).shouldAddAsset(bundle, asset)
+    ) {
       // If the asset is already the entry asset of a bundle, don't create a duplicate.
       if (isEntryAsset) {
         return;
       }
 
-      // No packager is available for this asset type. Create a new bundle with only this asset.
-      bundle.createSiblingBundle(asset);
+      // No packager is available for this asset type, or the packager doesn't support
+      // combining this asset into the bundle. Create a new bundle with only this asset.
+      bundle = bundle.createSiblingBundle(asset, dep);
     } else {
       // Add the asset to the common bundle of the asset's type
       bundle.getSiblingBundle(asset.type).addAsset(asset);
     }
 
-    // If the asset generated a representation for the parent bundle type, also add it there
-    if (asset.generated[bundle.type] != null) {
-      bundle.addAsset(asset);
-    }
-
     // Add the asset to sibling bundles for each generated type
     if (asset.type && asset.generated[asset.type]) {
       for (let t in asset.generated) {

src/builtins/loaders/browser/html-loader.js

@@ -0,0 +1,5 @@
+module.exports = function loadHTMLBundle(bundle) {
+  return fetch(bundle).then(function (res) {
+    return res.text();
+  });
+};

src/builtins/loaders/node/html-loader.js

@@ -0,0 +1,17 @@
+var fs = require('fs');
+
+module.exports = function loadHTMLBundle(bundle) {
+  return new Promise(function(resolve, reject) {
+    fs.readFile(__dirname + bundle, 'utf8', function(err, data) {
+      if (err) {
+        reject(err);
+      } else {
+        // wait for the next event loop iteration, so we are sure
+        // the current module is fully loaded
+        setImmediate(function() {
+          resolve(data);
+        });
+      }
+    });
+  });
+};

src/packagers/HTMLPackager.js

@@ -16,6 +16,11 @@ const metadataContent = new Set([
 ]);
 
 class HTMLPackager extends Packager {
+  static shouldAddAsset() {
+    // We cannot combine multiple HTML files together - they should be written as separate bundles.
+    return false;
+  }
+
   async addAsset(asset) {
     let html = asset.generated.html || '';
 

src/packagers/Packager.js

@@ -10,6 +10,10 @@ class Packager {
     this.options = bundler.options;
   }
 
+  static shouldAddAsset() {
+    return true;
+  }
+
   async setup() {
     // Create sub-directories if needed
     if (this.bundle.name.includes(path.sep)) {

src/packagers/RawPackager.js

@@ -3,6 +3,11 @@ const path = require('path');
 const fs = require('../utils/fs');
 
 class RawPackager extends Packager {
+  static shouldAddAsset() {
+    // We cannot combine multiple raw assets together - they should be written as separate bundles.
+    return false;
+  }
+
   // Override so we don't create a file for this bundle.
   // Each asset will be emitted as a separate file instead.
   setup() {}

test/integration/import-html-async/index.css

@@ -0,0 +1,3 @@
+body {
+  background: red;
+}

test/integration/import-html-async/index.js

@@ -0,0 +1 @@
+module.exports = import('./other.html');

test/integration/import-html-async/other.html

@@ -0,0 +1,10 @@
+<!doctype html>
+<html>
+<head>
+  <link rel="stylesheet" href="index.css" />
+</head>
+<body>
+  <h1>Other page</h1>
+  <img src="100x100.png" />
+</body>
+</html>

test/integration/import-html-sync/index.css

@@ -0,0 +1,3 @@
+body {
+  background: red;
+}

test/integration/import-html-sync/index.js

@@ -0,0 +1 @@
+output(require('./other.html'));

test/integration/import-html-sync/other.html

@@ -0,0 +1,10 @@
+<!doctype html>
+<html>
+<head>
+  <link rel="stylesheet" href="index.css" />
+</head>
+<body>
+  <h1>Other page</h1>
+  <img src="100x100.png" />
+</body>
+</html>

test/javascript.js

@@ -1,7 +1,7 @@
 const assert = require('assert');
 const fs = require('../src/utils/fs');
 const path = require('path');
-const {bundle, run, assertBundleTree} = require('./utils');
+const {bundle, run, assertBundleTree, deferred} = require('./utils');
 const {mkdirp} = require('../src/utils/fs');
 
 describe('javascript', function() {
@@ -1140,4 +1140,128 @@ describe('javascript', function() {
     let module = await run(b);
     assert.equal(module.default, 'Hello Hello!');
   });
+
+  it('should support importing HTML from JS async', async function() {
+    let b = await bundle(
+      __dirname + '/integration/import-html-async/index.js',
+      {sourceMaps: false}
+    );
+
+    await assertBundleTree(b, {
+      name: 'index.js',
+      assets: [
+        'index.js',
+        'bundle-loader.js',
+        'bundle-url.js',
+        'html-loader.js'
+      ],
+      childBundles: [
+        {
+          type: 'html',
+          assets: ['other.html'],
+          childBundles: [
+            {
+              type: 'png',
+              assets: ['100x100.png'],
+              childBundles: []
+            },
+            {
+              type: 'css',
+              assets: ['index.css'],
+              childBundles: []
+            }
+          ]
+        }
+      ]
+    });
+
+    let output = await run(b);
+    assert.equal(typeof output, 'string');
+    assert(output.includes('<html>'));
+    assert(output.includes('Other page'));
+  });
+
+  it('should support importing HTML from JS async with --target=node', async function() {
+    let b = await bundle(
+      __dirname + '/integration/import-html-async/index.js',
+      {
+        target: 'node',
+        sourceMaps: false
+      }
+    );
+
+    await assertBundleTree(b, {
+      name: 'index.js',
+      assets: [
+        'index.js',
+        'bundle-loader.js',
+        'bundle-url.js',
+        'html-loader.js'
+      ],
+      childBundles: [
+        {
+          type: 'html',
+          assets: ['other.html'],
+          childBundles: [
+            {
+              type: 'png',
+              assets: ['100x100.png'],
+              childBundles: []
+            },
+            {
+              type: 'css',
+              assets: ['index.css'],
+              childBundles: []
+            }
+          ]
+        }
+      ]
+    });
+
+    let output = await run(b);
+    assert.equal(typeof output, 'string');
+    assert(output.includes('<html>'));
+    assert(output.includes('Other page'));
+  });
+
+  it('should support importing HTML from JS sync', async function() {
+    let b = await bundle(__dirname + '/integration/import-html-sync/index.js', {
+      sourceMaps: false
+    });
+
+    await assertBundleTree(b, {
+      name: 'index.js',
+      assets: [
+        'index.js',
+        'bundle-loader.js',
+        'bundle-url.js',
+        'html-loader.js'
+      ],
+      childBundles: [
+        {
+          type: 'html',
+          assets: ['other.html'],
+          childBundles: [
+            {
+              type: 'png',
+              assets: ['100x100.png'],
+              childBundles: []
+            },
+            {
+              type: 'css',
+              assets: ['index.css'],
+              childBundles: []
+            }
+          ]
+        }
+      ]
+    });
+
+    let promise = deferred();
+    await run(b, {output: promise.resolve}, {require: false});
+    let output = await promise;
+    assert.equal(typeof output, 'string');
+    assert(output.includes('<html>'));
+    assert(output.includes('Other page'));
+  });
 });

test/utils.js

@@ -106,6 +106,11 @@ function prepareBrowserContext(bundle, globals) {
                 nodeFS.readFileSync(path.join(__dirname, 'dist', url))
               ).buffer
             );
+          },
+          text() {
+            return Promise.resolve(
+              nodeFS.readFileSync(path.join(__dirname, 'dist', url), 'utf8')
+            );
           }
         });
       }