Bug 1440269 - Defer calling debugger onNewScript hook for preloaded modules r=nbp

dom/script/ScriptLoader.cpp

@@ -2074,7 +2074,9 @@ ScriptLoader::FillCompileOptionsForRequest(const AutoJSAPI&jsapi,
     aOptions->setMutedErrors(!subsumes);
   }
 
-  if (!aRequest->IsModuleRequest()) {
+  if (aRequest->IsModuleRequest()) {
+    aOptions->hideScriptFromDebugger = true;
+  } else {
     JSContext* cx = jsapi.cx();
     JS::Rooted<JS::Value> elementVal(cx);
     MOZ_ASSERT(aRequest->mElement);
@@ -2245,6 +2247,10 @@ ScriptLoader::EvaluateScript(ScriptLoadRequest* aRequest)
         rv = nsJSUtils::InitModuleSourceElement(cx, module, aRequest->mElement);
         NS_ENSURE_SUCCESS(rv, rv);
         moduleScript->SetSourceElementAssociated();
+
+        // The script is now ready to be exposed to the debugger.
+        JS::Rooted<JSScript*> script(cx, JS::GetModuleScript(module));
+        JS::ExposeScriptToDebugger(cx, script);
       }
 
       rv = nsJSUtils::ModuleEvaluate(cx, module);

js/src/jsapi.cpp

@@ -3993,6 +3993,7 @@ JS::TransitiveCompileOptions::copyPODTransitiveOptions(const TransitiveCompileOp
     introductionOffset = rhs.introductionOffset;
     hasIntroductionInfo = rhs.hasIntroductionInfo;
     isProbablySystemOrAddonCode = rhs.isProbablySystemOrAddonCode;
+    hideScriptFromDebugger = rhs.hideScriptFromDebugger;
 };
 
 void
@@ -4678,6 +4679,17 @@ JS::InitScriptSourceElement(JSContext* cx, HandleScript script,
     return ScriptSourceObject::initElementProperties(cx, sso, element, elementAttrName);
 }
 
+JS_PUBLIC_API(void)
+JS::ExposeScriptToDebugger(JSContext* cx, HandleScript script)
+{
+    MOZ_ASSERT(cx);
+    MOZ_ASSERT(CurrentThreadCanAccessRuntime(cx->runtime()));
+
+    MOZ_ASSERT(script->hideScriptFromDebugger());
+    script->clearHideScriptFromDebugger();
+    Debugger::onNewScript(cx, script);
+}
+
 JS_PUBLIC_API(JSString*)
 JS_DecompileScript(JSContext* cx, HandleScript script)
 {

js/src/jsapi.h

@@ -3565,6 +3565,7 @@ class JS_FRIEND_API(TransitiveCompileOptions)
         sourceIsLazy(false),
         allowHTMLComments(true),
         isProbablySystemOrAddonCode(false),
+        hideScriptFromDebugger(false),
         introductionType(nullptr),
         introductionLineno(0),
         introductionOffset(0),
@@ -3600,6 +3601,7 @@ class JS_FRIEND_API(TransitiveCompileOptions)
     bool sourceIsLazy;
     bool allowHTMLComments;
     bool isProbablySystemOrAddonCode;
+    bool hideScriptFromDebugger;
 
     // |introductionType| is a statically allocated C string:
     // one of "eval", "Function", or "GeneratorFunction".
@@ -4007,6 +4009,13 @@ extern JS_PUBLIC_API(bool)
 InitScriptSourceElement(JSContext* cx, HandleScript script,
                         HandleObject element, HandleString elementAttrName = nullptr);
 
+/*
+ * For a script compiled with the hideScriptFromDebugger option, expose the
+ * script to the debugger by calling the debugger's onNewScript hook.
+ */
+extern JS_PUBLIC_API(void)
+ExposeScriptToDebugger(JSContext* cx, HandleScript script);
+
 } /* namespace JS */
 
 extern JS_PUBLIC_API(JSString*)

js/src/vm/Debugger.h

@@ -1800,6 +1800,11 @@ Debugger::onNewScript(JSContext* cx, HandleScript script)
     MOZ_ASSERT_IF(!script->compartment()->creationOptions().invisibleToDebugger() &&
                   !script->selfHosted(),
                   script->compartment()->firedOnNewGlobalObject);
+
+    // The script may not be ready to be interrogated by the debugger.
+    if (script->hideScriptFromDebugger())
+        return;
+
     if (script->compartment()->isDebuggee())
         slowPathOnNewScript(cx, script);
 }

js/src/vm/JSScript.cpp

@@ -2732,6 +2732,8 @@ JSScript::Create(JSContext* cx, const ReadOnlyCompileOptions& options,
     script->toStringStart_ = toStringStart;
     script->toStringEnd_ = toStringEnd;
 
+    script->hideScriptFromDebugger_ = options.hideScriptFromDebugger;
+
 #ifdef MOZ_VTUNE
     script->vtuneMethodId_ = vtune::GenerateUniqueMethodID();
 #endif
@@ -3625,6 +3627,7 @@ js::detail::CopyScript(JSContext* cx, HandleScript src, HandleScript dst,
     dst->isAsync_ = src->isAsync_;
     dst->hasRest_ = src->hasRest_;
     dst->isExprBody_ = src->isExprBody_;
+    dst->hideScriptFromDebugger_ = src->hideScriptFromDebugger_;
 
     if (nconsts != 0) {
         GCPtrValue* vector = Rebase<GCPtrValue>(dst, src, src->consts()->vector);

js/src/vm/JSScript.h

@@ -1142,6 +1142,9 @@ class JSScript : public js::gc::TenuredCell
     bool hasRest_:1;
     bool isExprBody_:1;
 
+    // True if the debugger's onNewScript hook has not yet been called.
+    bool hideScriptFromDebugger_:1;
+
     // Add padding so JSScript is gc::Cell aligned. Make padding protected
     // instead of private to suppress -Wunused-private-field compiler warnings.
   protected:
@@ -1463,6 +1466,13 @@ class JSScript : public js::gc::TenuredCell
         isExprBody_ = true;
     }
 
+    bool hideScriptFromDebugger() const {
+        return hideScriptFromDebugger_;
+    }
+    void clearHideScriptFromDebugger() {
+        hideScriptFromDebugger_ = false;
+    }
+
     void setNeedsHomeObject() {
         needsHomeObject_ = true;
     }