Issue #618 - Simplify module resolve hook to be a function pointer

This is an ahead-of time port to try and address #1624.
This is based on BZ 1461751 and Jon Coppeard's work in it.

dom/script/ScriptLoader.cpp

@@ -787,24 +787,20 @@ ScriptLoader::StartFetchingModuleAndDependencies(ModuleLoadRequest* aParent,
 }
 
 // 8.1.3.8.1 HostResolveImportedModule(referencingModule, specifier)
-bool
-HostResolveImportedModule(JSContext* aCx, unsigned argc, JS::Value* vp)
+JSObject*
+HostResolveImportedModule(JSContext* aCx, JS::Handle<JSObject*> aModule,
+                          JS::Handle<JSString*> aSpecifier)
 {
-  MOZ_ASSERT(argc == 2);
-  JS::CallArgs args = JS::CallArgsFromVp(argc, vp);
-  JS::Rooted<JSObject*> module(aCx, &args[0].toObject());
-  JS::Rooted<JSString*> specifier(aCx, args[1].toString());
-
   // Let referencing module script be referencingModule.[[HostDefined]].
-  JS::Value value = JS::GetModuleHostDefinedField(module);
+  JS::Value value = JS::GetModuleHostDefinedField(aModule);
   auto script = static_cast<ModuleScript*>(value.toPrivate());
-  MOZ_ASSERT(script->ModuleRecord() == module);
+  MOZ_ASSERT(script->ModuleRecord() == aModule);
 
   // Let url be the result of resolving a module specifier given referencing
   // module script and specifier.
   nsAutoJSString string;
-  if (!string.init(aCx, specifier)) {
-    return false;
+  if (!string.init(aCx, aSpecifier)) {
+    return nullptr;
   }
 
   nsCOMPtr<nsIURI> uri = ResolveModuleSpecifier(script, string);
@@ -820,27 +816,20 @@ HostResolveImportedModule(JSContext* aCx, unsigned argc, JS::Value* vp)
   MOZ_ASSERT(ms, "Resolved module not found in module map");
 
   MOZ_ASSERT(!ms->HasParseError());
+  MOZ_ASSERT(ms->ModuleRecord());
 
-  *vp = JS::ObjectValue(*ms->ModuleRecord());
-  return true;
+  return ms->ModuleRecord();
 }
 
-static nsresult
+static void
 EnsureModuleResolveHook(JSContext* aCx)
 {
-  if (JS::GetModuleResolveHook(aCx)) {
-    return NS_OK;
+  JSRuntime* rt = JS_GetRuntime(aCx);
+  if (JS::GetModuleResolveHook(rt)) {
+    return;
   }
 
-  JS::Rooted<JSFunction*> func(aCx);
-  func = JS_NewFunction(aCx, HostResolveImportedModule, 2, 0,
-                        "HostResolveImportedModule");
-  if (!func) {
-    return NS_ERROR_FAILURE;
-  }
-
-  JS::SetModuleResolveHook(aCx, func);
-  return NS_OK;
+  JS::SetModuleResolveHook(rt, HostResolveImportedModule);
 }
 
 void
@@ -928,8 +917,7 @@ ScriptLoader::InstantiateModuleTree(ModuleLoadRequest* aRequest)
     return false;
   }
 
-  nsresult rv = EnsureModuleResolveHook(jsapi.cx());
-  NS_ENSURE_SUCCESS(rv, false);
+  EnsureModuleResolveHook(jsapi.cx());
 
   JS::Rooted<JSObject*> module(jsapi.cx(), moduleScript->ModuleRecord());
   bool ok = NS_SUCCEEDED(nsJSUtils::ModuleInstantiate(jsapi.cx(), module));
@@ -1963,8 +1951,7 @@ ScriptLoader::EvaluateScript(ScriptLoadRequest* aRequest)
     }
 
     if (aRequest->IsModuleRequest()) {
-      rv = EnsureModuleResolveHook(cx);
-      NS_ENSURE_SUCCESS(rv, rv);
+      EnsureModuleResolveHook(cx);
 
       ModuleLoadRequest* request = aRequest->AsModuleRequest();
       MOZ_ASSERT(request->mModuleScript);

dom/script/ScriptLoader.h

@@ -579,8 +579,9 @@ private:
   RefPtr<mozilla::GenericPromise> WaitForModuleFetch(nsIURI* aURL);
   ModuleScript* GetFetchedModule(nsIURI* aURL) const;
 
-  friend bool
-  HostResolveImportedModule(JSContext* aCx, unsigned argc, JS::Value* vp);
+  friend JSObject*
+  HostResolveImportedModule(JSContext* aCx, JS::Handle<JSObject*> aModule,
+                          JS::Handle<JSString*> aSpecifier);
 
   nsresult CreateModuleScript(ModuleLoadRequest* aRequest);
   nsresult ProcessFetchedModuleSource(ModuleLoadRequest* aRequest);

js/public/Class.h

@@ -779,7 +779,7 @@ struct JSClass {
 // application.
 #define JSCLASS_GLOBAL_APPLICATION_SLOTS 5
 #define JSCLASS_GLOBAL_SLOT_COUNT                                             \
-    (JSCLASS_GLOBAL_APPLICATION_SLOTS + JSProto_LIMIT * 2 + 46)
+    (JSCLASS_GLOBAL_APPLICATION_SLOTS + JSProto_LIMIT * 2 + 45)
 #define JSCLASS_GLOBAL_FLAGS_WITH_SLOTS(n)                                    \
     (JSCLASS_IS_GLOBAL | JSCLASS_HAS_RESERVED_SLOTS(JSCLASS_GLOBAL_SLOT_COUNT + (n)))
 #define JSCLASS_GLOBAL_FLAGS                                                  \

js/src/jsapi.cpp

@@ -4667,21 +4667,16 @@ JS::Evaluate(JSContext* cx, const ReadOnlyCompileOptions& optionsArg,
     return ::Evaluate(cx, optionsArg, filename, rval);
 }
 
-JS_PUBLIC_API(JSFunction*)
-JS::GetModuleResolveHook(JSContext* cx)
+JS_PUBLIC_API(JS::ModuleResolveHook)
+JS::GetModuleResolveHook(JSRuntime* rt)
 {
-    AssertHeapIsIdle(cx);
-    CHECK_REQUEST(cx);
-    return cx->global()->moduleResolveHook();
+    return rt->moduleResolveHook;
 }
 
 JS_PUBLIC_API(void)
-JS::SetModuleResolveHook(JSContext* cx, HandleFunction func)
+JS::SetModuleResolveHook(JSRuntime* rt, JS::ModuleResolveHook func)
 {
-    AssertHeapIsIdle(cx);
-    CHECK_REQUEST(cx);
-    assertSameCompartment(cx, func);
-    cx->global()->setModuleResolveHook(func);
+    rt->moduleResolveHook = func;
 }
 
 JS_PUBLIC_API(bool)

js/src/jsapi.h

@@ -4325,17 +4325,19 @@ extern JS_PUBLIC_API(bool)
 Evaluate(JSContext* cx, const ReadOnlyCompileOptions& options,
          const char* filename, JS::MutableHandleValue rval);
 
-/**
- * Get the HostResolveImportedModule hook for a global.
- */
-extern JS_PUBLIC_API(JSFunction*)
-GetModuleResolveHook(JSContext* cx);
+using ModuleResolveHook = JSObject* (*)(JSContext*, HandleObject, HandleString);
 
 /**
- * Set the HostResolveImportedModule hook for a global to the given function.
+ * Get the HostResolveImportedModule hook for the runtime.
+ */
+extern JS_PUBLIC_API(ModuleResolveHook)
+GetModuleResolveHook(JSRuntime* rt);
+
+/**
+ * Set the HostResolveImportedModule hook for the runtime to the given function.
  */
 extern JS_PUBLIC_API(void)
-SetModuleResolveHook(JSContext* cx, JS::HandleFunction func);
+SetModuleResolveHook(JSRuntime* rt, ModuleResolveHook func);
 
 /**
  * Parse the given source buffer as a module in the scope of the current global

js/src/shell/js.cpp

@@ -274,6 +274,7 @@ struct ShellContext
     JS::PersistentRooted<JobQueue> jobQueue;
     ExclusiveData<ShellAsyncTasks> asyncTasks;
     bool drainingJobQueue;
+    JS::PersistentRootedFunction moduleResolveHook;
 
     /*
      * Watchdog thread state.
@@ -439,7 +440,8 @@ ShellContext::ShellContext(JSContext* cx)
     exitCode(0),
     quitting(false),
     readLineBufPos(0),
-    spsProfilingStackSize(0)
+    spsProfilingStackSize(0),
+    moduleResolveHook(cx)
 {}
 
 static ShellContext*
@@ -4030,13 +4032,34 @@ SetModuleResolveHook(JSContext* cx, unsigned argc, Value* vp)
         return false;
     }
 
-    RootedFunction hook(cx, &args[0].toObject().as<JSFunction>());
-    Rooted<GlobalObject*> global(cx, cx->global());
-    global->setModuleResolveHook(hook);
+    ShellContext* sc = GetShellContext(cx);
+    sc->moduleResolveHook = &args[0].toObject().as<JSFunction>();
+
     args.rval().setUndefined();
     return true;
 }
 
+static JSObject*
+CallModuleResolveHook(JSContext* cx, HandleObject module, HandleString specifier)
+{
+    ShellContext* sc = GetShellContext(cx);
+
+    JS::AutoValueArray<2> args(cx);
+    args[0].setObject(*module);
+    args[1].setString(specifier);
+
+    RootedValue result(cx);
+    if (!JS_CallFunction(cx, nullptr, sc->moduleResolveHook, args, &result))
+        return nullptr;
+
+    if (!result.isObject() || !result.toObject().is<ModuleObject>()) {
+         JS_ReportErrorASCII(cx, "Module resolve hook did not return Module object");
+         return nullptr;
+    }
+
+    return &result.toObject();
+}
+
 static bool
 GetModuleLoadPath(JSContext* cx, unsigned argc, Value* vp)
 {
@@ -7962,6 +7985,8 @@ main(int argc, char** argv, char** envp)
 
     js::SetPreserveWrapperCallback(cx, DummyPreserveWrapperCallback);
 
+    JS::SetModuleResolveHook(cx->runtime(), CallModuleResolveHook);
+
     result = Shell(cx, &op, envp);
 
 #ifdef DEBUG

js/src/vm/GlobalObject.h

@@ -119,7 +119,6 @@ class GlobalObject : public NativeObject
         DEBUGGERS,
         INTRINSICS,
         FOR_OF_PIC_CHAIN,
-        MODULE_RESOLVE_HOOK,
         WINDOW_PROXY,
         GLOBAL_THIS_RESOLVED,
 
@@ -879,19 +878,6 @@ class GlobalObject : public NativeObject
         setReservedSlot(WINDOW_PROXY, ObjectValue(*windowProxy));
     }
 
-    void setModuleResolveHook(HandleFunction hook) {
-        MOZ_ASSERT(hook);
-        setSlot(MODULE_RESOLVE_HOOK, ObjectValue(*hook));
-    }
-
-    JSFunction* moduleResolveHook() {
-        Value value = getSlotRef(MODULE_RESOLVE_HOOK);
-        if (value.isUndefined())
-            return nullptr;
-
-        return &value.toObject().as<JSFunction>();
-    }
-
     // Returns either this global's star-generator function prototype, or null
     // if that object was never created.  Dodgy; for use only in also-dodgy
     // GlobalHelperThreadState::mergeParseTaskCompartment().

js/src/vm/Runtime.cpp

@@ -241,8 +241,10 @@ JSRuntime::JSRuntime(JSRuntime* parentRuntime)
     lastAnimationTime(0),
     performanceMonitoring(thisFromCtor()),
     ionLazyLinkListSize_(0),
-    stackFormat_(parentRuntime ? js::StackFormat::Default
-                               : js::StackFormat::SpiderMonkey)
+    stackFormat_(parentRuntime ?
+                 js::StackFormat::Default :
+                 js::StackFormat::SpiderMonkey),
+    moduleResolveHook()
 {
     setGCStoreBufferPtr(&gc.storeBuffer);
 

js/src/vm/Runtime.h

@@ -1294,6 +1294,9 @@ struct JSRuntime : public JS::shadow::Runtime,
     // For inherited heap state accessors.
     friend class js::gc::AutoTraceSession;
     friend class JS::AutoEnterCycleCollection;
+
+    // The implementation-defined abstract operation HostResolveImportedModule.
+    JS::ModuleResolveHook moduleResolveHook;
 };
 
 namespace js {

js/src/vm/SelfHosting.cpp

@@ -2026,25 +2026,26 @@ intrinsic_HostResolveImportedModule(JSContext* cx, unsigned argc, Value* vp)
 {
     CallArgs args = CallArgsFromVp(argc, vp);
     MOZ_ASSERT(args.length() == 2);
-    MOZ_ASSERT(args[0].toObject().is<ModuleObject>());
-    MOZ_ASSERT(args[1].isString());
+    RootedModuleObject module(cx, &args[0].toObject().as<ModuleObject>());
+    RootedString specifier(cx, args[1].toString());
 
-    RootedFunction moduleResolveHook(cx, cx->global()->moduleResolveHook());
+    JS::ModuleResolveHook moduleResolveHook = cx->runtime()->moduleResolveHook;
     if (!moduleResolveHook) {
         JS_ReportErrorASCII(cx, "Module resolve hook not set");
         return false;
     }
 
-    RootedValue result(cx);
-    if (!JS_CallFunction(cx, nullptr, moduleResolveHook, args, &result))
+    RootedObject result(cx);
+    result = moduleResolveHook(cx, module, specifier);
+    if (!result)
         return false;
 
-    if (!result.isObject() || !result.toObject().is<ModuleObject>()) {
+    if (!result->is<ModuleObject>()) {
         JS_ReportErrorASCII(cx, "Module resolve hook did not return Module object");
         return false;
     }
 
-    args.rval().set(result);
+    args.rval().setObject(*result);
     return true;
 }