From 7e84625365ca7831724da2f91ebd6bd44a36ad3f Mon Sep 17 00:00:00 2001
From: Jon Coppeard <jcoppeard@mozilla.com>
Date: Fri, 18 Nov 2022 13:25:47 +0000
Subject: [PATCH] Bug 1774111 - Check for already-completed request in
 ModuleLoaderBase::FinishDynamicImport r=yulia

I've looked at this for a while and still don't know how this can happen but it
does seem reasonable to add a check here that we haven't already completed the
request.

Depends on D162386

Differential Revision: https://phabricator.services.mozilla.com/D162387
---
 js/loader/ModuleLoaderBase.cpp | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/js/loader/ModuleLoaderBase.cpp b/js/loader/ModuleLoaderBase.cpp
index c1939d3990ef..3e962d0be2a6 100644
--- a/js/loader/ModuleLoaderBase.cpp
+++ b/js/loader/ModuleLoaderBase.cpp
@@ -267,6 +267,9 @@ bool ModuleLoaderBase::HostPopulateImportMeta(
 bool ModuleLoaderBase::HostImportModuleDynamically(
     JSContext* aCx, JS::Handle<JS::Value> aReferencingPrivate,
     JS::Handle<JSObject*> aModuleRequest, JS::Handle<JSObject*> aPromise) {
+  MOZ_DIAGNOSTIC_ASSERT(aModuleRequest);
+  MOZ_DIAGNOSTIC_ASSERT(aPromise);
+
   RefPtr<LoadedScript> script(GetLoadedScriptOrNull(aCx, aReferencingPrivate));
 
   JS::Rooted<JSString*> specifierString(
@@ -945,6 +948,11 @@ void ModuleLoaderBase::FinishDynamicImport(
   // Complete the dynamic import, report failures indicated by aResult or as a
   // pending exception on the context.
 
+  if (!aRequest->mDynamicPromise) {
+    // Import has already been completed.
+    return;
+  }
+
   if (NS_FAILED(aResult) &&
       aResult != NS_SUCCESS_DOM_SCRIPT_EVALUATION_THREW_UNCATCHABLE) {
     MOZ_ASSERT(!JS_IsExceptionPending(aCx));