Bug 1602741 - Ensure shell drainJobQueue() function always drains the job queue r=sfink

Previously this wouldn't drain any jobs queued by FinalizationGroup callbacks.

Differential Revision: https://phabricator.services.mozilla.com/D56538

--HG--
extra : moz-landing-system : lando

js/src/jit-test/tests/gc/bug-1602741.js

@@ -0,0 +1,26 @@
+// |jit-test| --enable-weak-refs
+
+// Test that drainJobQueue() drains all jobs, including those queued
+// by FinalizationGroup callbacks.
+
+let finalizeRan = false;
+let promiseRan = false;
+
+let fg = new FinalizationGroup(() => {
+  finalizeRan = true;
+  Promise.resolve().then(() => {
+    promiseRan = true;
+  });
+});
+
+fg.register({}, {});
+
+gc();
+
+assertEq(finalizeRan, false);
+assertEq(promiseRan, false);
+
+drainJobQueue();
+
+assertEq(finalizeRan, true);
+assertEq(promiseRan, true);

js/src/shell/js.cpp

@@ -1030,13 +1030,16 @@ static void ShellCleanupFinalizationGroupCallback(JSObject* group, void* data) {
   }
 }
 
-static void MaybeRunFinalizationGroupCleanupTasks(JSContext* cx) {
+// Run any FinalizationGroup cleanup tasks and return whether any ran.
+static bool MaybeRunFinalizationGroupCleanupTasks(JSContext* cx) {
   ShellContext* sc = GetShellContext(cx);
   MOZ_ASSERT(!sc->quitting);
 
   Rooted<ShellContext::ObjectVector> groups(cx);
   std::swap(groups.get(), sc->finalizationGroupsToCleanUp.get());
 
+  bool ranTasks = false;
+
   RootedObject group(cx);
   for (const auto& g : groups) {
     group = g;
@@ -1048,10 +1051,14 @@ static void MaybeRunFinalizationGroupCleanupTasks(JSContext* cx) {
       mozilla::Unused << JS::CleanupQueuedFinalizationGroup(cx, group);
     }
 
+    ranTasks = true;
+
     if (sc->quitting) {
       break;
     }
   }
+
+  return ranTasks;
 }
 
 static bool EnqueueJob(JSContext* cx, unsigned argc, Value* vp) {
@@ -1074,14 +1081,19 @@ static void RunShellJobs(JSContext* cx) {
     return;
   }
 
-  // Run microtasks.
-  js::RunJobs(cx);
-  if (sc->quitting) {
-    return;
-  }
+  while (true) {
+    // Run microtasks.
+    js::RunJobs(cx);
+    if (sc->quitting) {
+      return;
+    }
 
-  // Run tasks (only finalization group clean tasks are possible).
-  MaybeRunFinalizationGroupCleanupTasks(cx);
+    // Run tasks (only finalization group clean tasks are possible).
+    bool ranTasks = MaybeRunFinalizationGroupCleanupTasks(cx);
+    if (!ranTasks) {
+      break;
+    }
+  }
 }
 
 static bool DrainJobQueue(JSContext* cx, unsigned argc, Value* vp) {