feat: add publicPath support (options.publicPath) (#31)

.gitignore

@@ -1,2 +1,3 @@
 node_modules
 test/expected
+.idea

README.md

@@ -64,6 +64,7 @@ worker.addEventListener("message", function (event) {})
 |**`name`**|`{String}`|`[hash].worker.js`|Set a custom name for the output script|
 |**`inline`**|`{Boolean}`|`false`|Inline the worker as a BLOB|
 |**`fallback`**|`{Boolean}`|`false`|Require a fallback for non-worker supporting environments|
+|**`publicPath`**|`{String}`|`null`|Override the path from which worker scripts are downloaded|
 
 ### `name`
 
@@ -130,6 +131,18 @@ self.postMessage({ foo: 'foo' })
 self.addEventListener('message', (event) => console.log(event))  
 ```
 
+### `publicPath`
+
+Overrides the path from which worker scripts are downloaded. If not specified, the same public path used for other 
+webpack assets is used.
+
+```js
+{
+  loader: 'worker-loader'
+  options: { publicPath: '/scripts/workers/' }
+}
+```
+
 ### `Integrating with ES2015 Modules`
 
 > ℹ️  You can even use ES2015 Modules if you have the [`babel-loader`](https://github.com/babel/babel-loader) configured.
@@ -187,6 +200,27 @@ worker.onmessage = (event) => {};
 worker.addEventListener("message", (event) => {});
 ```
 
+### Cross-origin policy workarounds
+
+Web Workers are restricted by a same-origin policy, so if your webpack assets are not being served from the same origin
+as your application, their download may be blocked by your browser. This scenario can commonly occur if you are hosting
+your assets under a CDN domain. Even downloads from the webpack dev server could be blocked.
+
+There are two workarounds. Firstly, you can inline the worker as a blob instead of downloading it as an external
+script via the [`inline`](#inline) parameter:
+
+``` javascript
+var MyWorker = require("worker?inline!./file.js");
+```
+
+Secondly, you may override the base download URL for your worker script via the [`publicPath`](#publicpath) option.
+
+```javascript
+// This will cause the worker to be downloaded from `/workers/file.js`
+var MyWorker = require("worker?publicPath=%2Fworkers%2F!./file.js");
+```
+
+
 <h2 align="center">Maintainers</h2>
 
 <table>

index.js

@@ -9,7 +9,8 @@ const SingleEntryPlugin = require('webpack/lib/SingleEntryPlugin');
 const schema = require('./options.json');
 
 const getWorker = (file, content, options) => {
-  const workerPublicPath = `__webpack_public_path__ + ${JSON.stringify(file)}`;
+  const publicPath = options.publicPath ? JSON.stringify(options.publicPath) : '__webpack_public_path__';
+  const workerPublicPath = `${publicPath} + ${JSON.stringify(file)}`;
   if (options.inline) {
     const createInlineWorkerPath = JSON.stringify(`!!${path.join(__dirname, 'createInlineWorker.js')}`);
     const fallbackWorkerPath = options.fallback === false ? 'null' : workerPublicPath;

options.json

@@ -9,6 +9,9 @@
     },
     "fallback": {
       "type": "boolean"
+    },
+    "publicPath": {
+      "type": "string"
     }
   },
   "additionalProperties": false

test/fixtures/public-path-override/entry.js

@@ -0,0 +1 @@
+const Worker = require('./worker.js');

test/fixtures/public-path-override/worker.js

@@ -0,0 +1 @@
+// named worker test mark

test/index.js

@@ -226,4 +226,26 @@ describe('worker-loader', () => {
       })
     );
   });
+
+  it('should use the publicPath option as the base URL if specified', () =>
+    makeBundle('public-path-override', {
+      module: {
+        rules: [
+          {
+            test: /worker\.js$/,
+            loader: '../index.js',
+            options: {
+              publicPath: '/some/proxy/',
+            },
+          },
+        ],
+      },
+    }).then((stats) => {
+      const assets = stats.compilation.assets;
+      const bundle = assets['bundle.js'];
+      const workerFile = Object.keys(assets).find(name => /worker\.js$/.test(name));
+
+      assert.notEqual(bundle._cachedSource.indexOf(`new Worker("/some/proxy/" + "${workerFile}")`), -1);
+    })
+  );
 });