always `loadScript` with a script tag (#6411)

to avoid Content Security Policy unsafe-line violations

app/assets/javascripts/admin/components/ace-editor.js.es6

@@ -1,8 +1,6 @@
 import loadScript from "discourse/lib/load-script";
 import { observes } from "ember-addons/ember-computed-decorators";
 
-const LOAD_ASYNC = !Ember.testing;
-
 export default Ember.Component.extend({
   mode: "css",
   classNames: ["ace-wrapper"],
@@ -26,7 +24,7 @@ export default Ember.Component.extend({
 
   @observes("mode")
   modeChanged() {
-    if (LOAD_ASYNC && this._editor && !this._skipContentChangeEvent) {
+    if (this._editor && !this._skipContentChangeEvent) {
       this._editor.getSession().setMode("ace/mode/" + this.get("mode"));
     }
   },
@@ -71,21 +69,17 @@ export default Ember.Component.extend({
   didInsertElement() {
     this._super();
 
-    loadScript("/javascripts/ace/ace.js", { scriptTag: true }).then(() => {
+    loadScript("/javascripts/ace/ace.js").then(() => {
       window.ace.require(["ace/ace"], loadedAce => {
         if (!this.element || this.isDestroying || this.isDestroyed) {
           return;
         }
         const editor = loadedAce.edit(this.$(".ace")[0]);
 
-        if (LOAD_ASYNC) {
-          editor.setTheme("ace/theme/chrome");
-        }
+        editor.setTheme("ace/theme/chrome");
         editor.setShowPrintMargin(false);
         editor.setOptions({ fontSize: "14px" });
-        if (LOAD_ASYNC) {
-          editor.getSession().setMode("ace/mode/" + this.get("mode"));
-        }
+        editor.getSession().setMode("ace/mode/" + this.get("mode"));
         editor.on("change", () => {
           this._skipContentChangeEvent = true;
           this.set("content", editor.getSession().getValue());

app/assets/javascripts/discourse/lib/load-script.js.es6

@@ -44,7 +44,7 @@ export default function loadScript(url, opts) {
   $("script").each((i, tag) => {
     const src = tag.getAttribute("src");
 
-    if (src && (opts.scriptTag || src !== url)) {
+    if (src && src !== url) {
       _loaded[tag.getAttribute("src")] = true;
     }
   });
@@ -86,22 +86,15 @@ export default function loadScript(url, opts) {
       cdnUrl = Discourse.CDN.replace(/\/$/, "") + url;
     }
 
-    // Some javascript depends on the path of where it is loaded (ace editor)
-    // to dynamically load more JS. In that case, add the `scriptTag: true`
-    // option.
-    if (opts.scriptTag) {
-      if (Ember.testing) {
-        throw new Error(
-          `In test mode scripts cannot be loaded async ${cdnUrl}`
-        );
-      }
-      loadWithTag(cdnUrl, cb);
-    } else {
+    if (opts.css) {
       ajax({
         url: cdnUrl,
-        dataType: opts.css ? "text" : "script",
+        dataType: "text",
         cache: true
       }).then(cb);
+    } else {
+      // Always load JavaScript with script tag to avoid Content Security Policy inline violations
+      loadWithTag(cdnUrl, cb);
     }
   });
 }

test/javascripts/lib/load-script-test.js.es6

@@ -0,0 +1,24 @@
+import loadScript from "discourse/lib/load-script";
+
+QUnit.module("lib:load-script");
+
+QUnit.test(
+  "load with a script tag, and callbacks are only executed after script is loaded",
+  async assert => {
+    const src = "/javascripts/ace/ace.js";
+
+    await loadScript(src).then(() => {
+      assert.ok(
+        typeof ace !== "undefined",
+        "callbacks should only be executed after the script has fully loaded"
+      );
+
+      // cannot use the `find` test helper here because the script tag is injected outside of the test sandbox frame
+      const scriptTags = Array.from(document.getElementsByTagName("script"));
+      assert.ok(
+        scriptTags.some(scriptTag => scriptTag.src.includes(src)),
+        "the script should be loaded with a script tag"
+      );
+    });
+  }
+);

test/javascripts/test_helper.js

@@ -52,7 +52,6 @@ window.MessageBus.stop();
 
 // Trick JSHint into allow document.write
 var d = document;
-d.write('<script src="/javascripts/ace/ace.js"></script>');
 d.write(
   '<div id="ember-testing-container"><div id="ember-testing"></div></div>'
 );