From 0d0a52e249b18fe9363283bec3a6cab720fa8fb4 Mon Sep 17 00:00:00 2001
From: Austin Morton <austinpmorton@gmail.com>
Date: Wed, 13 Nov 2019 23:09:11 -0500
Subject: [PATCH] "Fix" cross origin monaco web workers

This is a workaround to make cross origin monaco web workers function
in spite of the monaco webpack plugin hijacking the MonacoEnvironment global.

see https://github.com/microsoft/monaco-editor-webpack-plugin/issues/42

This workaround wouldn't be so bad, if it didn't _also_ rely on *another* bug to
actually work.

The webpack plugin incorrectly uses
    window.__webpack_public_path__
when it should use
    __webpack_public_path__

see https://github.com/microsoft/monaco-editor-webpack-plugin/pull/63

We can leave __webpack_public_path__ with the correct value, which lets runtime chunk
loading continue to function correctly.

We can then set window.__webpack_public_path__ to the below handler, which lets us
fabricate a worker on the fly.

This is bad and I feel bad.
---
 app.js            | 30 ++++++++++++++++++++++++++++++
 static/options.js |  4 +++-
 2 files changed, 33 insertions(+), 1 deletion(-)

diff --git a/app.js b/app.js
index 600463da12b..687123e6973 100755
--- a/app.js
+++ b/app.js
@@ -502,6 +502,36 @@ aws.initConfig(awsProps)
                 const shortenerLib = require(`./lib/shortener-${clientOptionsHandler.options.urlShortenService}`);
                 const shortener = shortenerLib({storageHandler});
 
+                /*
+                 * This is a workaround to make cross origin monaco web workers function
+                 * in spite of the monaco webpack plugin hijacking the MonacoEnvironment global.
+                 *
+                 * see https://github.com/microsoft/monaco-editor-webpack-plugin/issues/42
+                 *
+                 * This workaround wouldn't be so bad, if it didn't _also_ rely on *another* bug to
+                 * actually work.
+                 *
+                 * The webpack plugin incorrectly uses
+                 *     window.__webpack_public_path__
+                 * when it should use
+                 *     __webpack_public_path__
+                 *
+                 * see https://github.com/microsoft/monaco-editor-webpack-plugin/pull/63
+                 *
+                 * We can leave __webpack_public_path__ with the correct value, which lets runtime chunk
+                 * loading continue to function correctly.
+                 *
+                 * We can then set window.__webpack_public_path__ to the below handler, which lets us
+                 * fabricate a worker on the fly.
+                 *
+                 * This is bad and I feel bad.
+                 */
+                router.get('/workers/:worker', (req, res) => {
+                    staticHeaders(res);
+                    res.set('Content-Type', 'application/javascript');
+                    res.end(`importScripts('${urljoin(staticRoot, req.params.worker)}');`);
+                });
+
                 router
                     .use(Sentry.Handlers.requestHandler())
                     .use(morgan(morganFormat, {
diff --git a/static/options.js b/static/options.js
index 3ba2dada119..78e2e235c0a 100644
--- a/static/options.js
+++ b/static/options.js
@@ -35,6 +35,8 @@ for (var k in extraOptions) {
 }
 
 __webpack_public_path__ = window.staticRoot;
-window.__webpack_public_path__ = __webpack_public_path__;
+
+// really gross monaco web worker cross origin workaround
+window.__webpack_public_path__ = window.httpRoot + 'workers/';
 
 module.exports = window.compilerExplorerOptions;