From 8db81508a1ffe1c3873503a1cb2082d664714776 Mon Sep 17 00:00:00 2001
From: Gaming4JC <g4jc@hyperbola.info>
Date: Mon, 20 Jan 2020 20:14:59 -0500
Subject: Bug 1415761 - Catch the exception and rethrow it after invoking
 custom elements reactions;

The spec was unclear on how CEReactions interact with thrown exceptions; see https://github.com/whatwg/html/issues/3217. The spec is now being clarified in https://github.com/whatwg/html/pull/3235.

Tag UXP Issue #1344
---
 dom/base/CustomElementRegistry.h | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

(limited to 'dom/base/CustomElementRegistry.h')

diff --git a/dom/base/CustomElementRegistry.h b/dom/base/CustomElementRegistry.h
index c180a10af..51c97fd5e 100644
--- a/dom/base/CustomElementRegistry.h
+++ b/dom/base/CustomElementRegistry.h
@@ -472,15 +472,24 @@ public:
 
 class MOZ_RAII AutoCEReaction final {
   public:
-    explicit AutoCEReaction(CustomElementReactionsStack* aReactionsStack)
-      : mReactionsStack(aReactionsStack) {
+    // JSContext is allowed to be a nullptr if we are guaranteeing that we're
+    // not doing something that might throw but not finish reporting a JS
+    // exception during the lifetime of the AutoCEReaction.
+    AutoCEReaction(CustomElementReactionsStack* aReactionsStack, JSContext* aCx)
+      : mReactionsStack(aReactionsStack)
+      , mCx(aCx) {
       mReactionsStack->CreateAndPushElementQueue();
     }
     ~AutoCEReaction() {
+      Maybe<JS::AutoSaveExceptionState> ases;
+      if (mCx) {
+        ases.emplace(mCx);
+      }
       mReactionsStack->PopAndInvokeElementQueue();
     }
   private:
     RefPtr<CustomElementReactionsStack> mReactionsStack;
+    JSContext* mCx;
 };
 
 } // namespace dom
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