From 408d61b4f08bc71bddf74d6d575c0e19355ee07e Mon Sep 17 00:00:00 2001
From: janekptacijarabaci <janekptacijarabaci@seznam.cz>
Date: Sat, 14 Apr 2018 08:45:16 +0200
Subject: [PATCH] Bug 1330657 - Enable <script type="module"> behind a pref

---
 dom/base/nsScriptLoader.cpp | 18 +++++++++++++++---
 dom/base/nsScriptLoader.h   |  2 ++
 modules/libpref/init/all.js |  3 +++
 3 files changed, 20 insertions(+), 3 deletions(-)

diff --git a/dom/base/nsScriptLoader.cpp b/dom/base/nsScriptLoader.cpp
index 1e23d6c5ff..5577df20bc 100644
--- a/dom/base/nsScriptLoader.cpp
+++ b/dom/base/nsScriptLoader.cpp
@@ -653,6 +653,19 @@ nsScriptLoader::CheckContentPolicy(nsIDocument* aDocument,
   return NS_OK;
 }
 
+bool
+nsScriptLoader::ModuleScriptsEnabled()
+{
+  static bool sEnabledForContent = false;
+  static bool sCachedPref = false;
+  if (!sCachedPref) {
+    sCachedPref = true;
+    Preferences::AddBoolVarCache(&sEnabledForContent, "dom.moduleScripts.enabled", false);
+  }
+
+  return nsContentUtils::IsChromeDoc(mDocument) || sEnabledForContent;
+}
+
 bool
 nsScriptLoader::ModuleMapContainsModule(nsModuleLoadRequest *aRequest) const
 {
@@ -1448,8 +1461,7 @@ nsScriptLoader::ProcessScriptElement(nsIScriptElement *aElement)
 
   nsScriptKind scriptKind = nsScriptKind::Classic;
   if (!type.IsEmpty()) {
-    // Support type="module" only for chrome documents.
-    if (nsContentUtils::IsChromeDoc(mDocument) && type.LowerCaseEqualsASCII("module")) {
+    if (ModuleScriptsEnabled() && type.LowerCaseEqualsASCII("module")) {
       scriptKind = nsScriptKind::Module;
     } else {
       NS_ENSURE_TRUE(ParseTypeAttribute(type, &version), false);
@@ -2768,7 +2780,7 @@ nsScriptLoader::PreloadURI(nsIURI *aURI, const nsAString &aCharset,
   }
 
   // TODO: Preload module scripts.
-  if (nsContentUtils::IsChromeDoc(mDocument) && aType.LowerCaseEqualsASCII("module")) {
+  if (ModuleScriptsEnabled() && aType.LowerCaseEqualsASCII("module")) {
     return;
   }
 
diff --git a/dom/base/nsScriptLoader.h b/dom/base/nsScriptLoader.h
index d30a58441e..a00239be5f 100644
--- a/dom/base/nsScriptLoader.h
+++ b/dom/base/nsScriptLoader.h
@@ -568,6 +568,8 @@ private:
   JS::SourceBufferHolder GetScriptSource(nsScriptLoadRequest* aRequest,
                                          nsAutoString& inlineData);
 
+  bool ModuleScriptsEnabled();
+
   void SetModuleFetchStarted(nsModuleLoadRequest *aRequest);
   void SetModuleFetchFinishedAndResumeWaitingRequests(nsModuleLoadRequest *aRequest,
                                                       nsresult aResult);
diff --git a/modules/libpref/init/all.js b/modules/libpref/init/all.js
index 78446ee859..7ca5cdf688 100644
--- a/modules/libpref/init/all.js
+++ b/modules/libpref/init/all.js
@@ -5494,3 +5494,6 @@ pref("dom.storageManager.enabled", false);
 // >0 = suppress further prompts after the user has canceled the dialog n times
 // See application preferences for appropriate defaults.
 pref("prompts.authentication_dialog_abuse_limit", 0);
+
+// Whether module scripts (<script type="module">) are enabled for content.
+pref("dom.moduleScripts.enabled", false);