Bug 1482153 - Replace ModuleObject's host defined field with one on top-level JSScripts r=jandem r=hsivonen

dom/script/ModuleScript.cpp

@@ -56,9 +56,8 @@ ModuleScript::UnlinkScript()
 {
   // Remove module's back reference to this object request if present.
   if (mScript) {
-    MOZ_ASSERT(JS::GetModuleHostDefinedField(mScript).toPrivate() ==
-               this);
-    JS::SetModuleHostDefinedField(mScript, JS::UndefinedValue());
+    MOZ_ASSERT(JS::GetTopLevelScriptPrivate(mScript) == this);
+    JS::SetTopLevelScriptPrivate(mScript, nullptr);
     mScript = nullptr;
   }
 }
@@ -81,7 +80,7 @@ ModuleScript::SetScript(JS::Handle<JSScript*> aScript)
 
   // Make module's host defined field point to this module script object.
   // This is cleared in the UnlinkScript().
-  JS::SetModuleHostDefinedField(mScript, JS::PrivateValue(this));
+  JS::SetTopLevelScriptPrivate(mScript, this);
   HoldJSObjects(this);
 }
 

dom/script/ScriptLoader.cpp

@@ -760,8 +760,13 @@ HostResolveImportedModule(JSContext* aCx, JS::Handle<JSScript*> aScript,
                           JS::Handle<JSString*> aSpecifier)
 {
   // Let referencing module script be referencingModule.[[HostDefined]].
-  JS::Value value = JS::GetModuleHostDefinedField(aScript);
-  auto script = static_cast<ModuleScript*>(value.toPrivate());
+  void* value = JS::GetTopLevelScriptPrivate(aScript);
+  if (!value) {
+    JS_ReportErrorASCII(aCx, "Module script not found");
+    return nullptr;
+  }
+
+  auto script = static_cast<ModuleScript*>(value);
   MOZ_ASSERT(script->Script() == aScript);
 
   // Let url be the result of resolving a module specifier given referencing
@@ -794,13 +799,13 @@ HostPopulateImportMeta(JSContext* aCx, JS::Handle<JSScript*> aScript,
 {
   MOZ_DIAGNOSTIC_ASSERT(aScript);
 
-  JS::Value value = JS::GetModuleHostDefinedField(aScript);
-  if (value.isUndefined()) {
+  void* value = JS::GetTopLevelScriptPrivate(aScript);
+  if (!value) {
     JS_ReportErrorASCII(aCx, "Module script not found");
     return false;
   }
 
-  auto script = static_cast<ModuleScript*>(value.toPrivate());
+  auto script = static_cast<ModuleScript*>(value);
   MOZ_DIAGNOSTIC_ASSERT(script->Script() == aScript);
 
   nsAutoCString url;

js/src/builtin/ModuleObject.cpp

@@ -1010,18 +1010,6 @@ ModuleObject::setMetaObject(JSObject* obj)
     setReservedSlot(MetaObjectSlot, ObjectValue(*obj));
 }
 
-Value
-ModuleObject::hostDefinedField() const
-{
-    return getReservedSlot(HostDefinedSlot);
-}
-
-void
-ModuleObject::setHostDefinedField(const JS::Value& value)
-{
-    setReservedSlot(HostDefinedSlot, value);
-}
-
 Scope*
 ModuleObject::enclosingScope() const
 {

js/src/builtin/ModuleObject.h

@@ -255,7 +255,6 @@ class ModuleObject : public NativeObject
         StatusSlot,
         EvaluationErrorSlot,
         MetaObjectSlot,
-        HostDefinedSlot,
         RequestedModulesSlot,
         ImportEntriesSlot,
         LocalExportEntriesSlot,
@@ -306,7 +305,6 @@ class ModuleObject : public NativeObject
     bool hadEvaluationError() const;
     Value evaluationError() const;
     JSObject* metaObject() const;
-    Value hostDefinedField() const;
     ArrayObject& requestedModules() const;
     ArrayObject& importEntries() const;
     ArrayObject& localExportEntries() const;
@@ -319,8 +317,6 @@ class ModuleObject : public NativeObject
 
     void setMetaObject(JSObject* obj);
 
-    void setHostDefinedField(const JS::Value& value);
-
     // For BytecodeEmitter.
     bool noteFunctionDeclaration(JSContext* cx, HandleAtom name, HandleFunction fun);
 

js/src/builtin/SelfHostingDefines.h

@@ -99,8 +99,8 @@
 #define MODULE_OBJECT_ENVIRONMENT_SLOT        1
 #define MODULE_OBJECT_STATUS_SLOT             3
 #define MODULE_OBJECT_EVALUATION_ERROR_SLOT   4
-#define MODULE_OBJECT_DFS_INDEX_SLOT          14
-#define MODULE_OBJECT_DFS_ANCESTOR_INDEX_SLOT 15
+#define MODULE_OBJECT_DFS_INDEX_SLOT          13
+#define MODULE_OBJECT_DFS_ANCESTOR_INDEX_SLOT 14
 
 #define MODULE_STATUS_UNINSTANTIATED  0
 #define MODULE_STATUS_INSTANTIATING   1

js/src/jsapi.cpp

@@ -4869,17 +4869,17 @@ JS::CompileModule(JSContext* cx, const ReadOnlyCompileOptions& options,
 }
 
 JS_PUBLIC_API(void)
-JS::SetModuleHostDefinedField(JSScript* script, const JS::Value& value)
+JS::SetTopLevelScriptPrivate(JSScript* script, void* value)
 {
-    MOZ_ASSERT(script->module());
-    script->module()->setHostDefinedField(value);
+    MOZ_ASSERT(script);
+    script->setTopLevelPrivate(value);
 }
 
-JS_PUBLIC_API(JS::Value)
-JS::GetModuleHostDefinedField(JSScript* script)
+JS_PUBLIC_API(void*)
+JS::GetTopLevelScriptPrivate(JSScript* script)
 {
-    MOZ_ASSERT(script->module());
-    return script->module()->hostDefinedField();
+    MOZ_ASSERT(script);
+    return script->maybeTopLevelPrivate();
 }
 
 JS_PUBLIC_API(bool)

js/src/jsapi.h

@@ -3915,17 +3915,16 @@ CompileModule(JSContext* cx, const ReadOnlyCompileOptions& options,
               SourceBufferHolder& srcBuf, JS::MutableHandleScript script);
 
 /**
- * Set the [[HostDefined]] field of a source text module record to the given
- * value.
+ * Set the [[HostDefined]] field of a classic script or module script.
  */
 extern JS_PUBLIC_API(void)
-SetModuleHostDefinedField(JSScript* module, const JS::Value& value);
+SetTopLevelScriptPrivate(JSScript* script, void* value);
 
 /**
- * Get the [[HostDefined]] field of a source text module record.
+ * Get the [[HostDefined]] field of a classic script or module script.
  */
-extern JS_PUBLIC_API(JS::Value)
-GetModuleHostDefinedField(JSScript* script);
+extern JS_PUBLIC_API(void*)
+GetTopLevelScriptPrivate(JSScript* script);
 
 /*
  * Perform the ModuleInstantiate operation on the given source text module

js/src/vm/JSScript.cpp

@@ -4491,6 +4491,35 @@ JSScript::AutoDelazify::dropScript()
     script_ = nullptr;
 }
 
+void
+JSScript::setTopLevelPrivate(void* value)
+{
+    MOZ_ASSERT(module() || isGlobalCode());
+
+    Scope* scope = bodyScope();
+    if (scope->is<GlobalScope>())
+        scope->as<GlobalScope>().setTopLevelPrivate(value);
+    else if (scope->is<ModuleScope>())
+        scope->as<ModuleScope>().setTopLevelPrivate(value);
+    else
+        MOZ_CRASH("Unexpected scope kind");
+}
+
+void*
+JSScript::maybeTopLevelPrivate() const
+{
+    if (!module() || !isGlobalCode())
+        return nullptr;
+
+    Scope* scope = bodyScope();
+    if (scope->is<GlobalScope>())
+        return scope->as<GlobalScope>().topLevelPrivate();
+    else if (scope->is<ModuleScope>())
+        return scope->as<ModuleScope>().topLevelPrivate();
+
+    MOZ_CRASH("Unexpected scope kind");
+}
+
 JS::ubi::Node::Size
 JS::ubi::Concrete<JSScript>::size(mozilla::MallocSizeOf mallocSizeOf) const
 {

js/src/vm/JSScript.h

@@ -1760,8 +1760,13 @@ class JSScript : public js::gc::TenuredCell
      *
      * If this script has a function associated to it, then it is not the
      * top-level of a file.
+     *
+     * Note that this can returns true for eval scripts as well as global
+     * scripts and modules.
      */
-    bool isTopLevel() { return code() && !functionNonDelazifying(); }
+    bool isTopLevel() const {
+        return code() && !functionNonDelazifying();
+    }
 
     /* Ensure the script has a TypeScript. */
     inline bool ensureHasTypes(JSContext* cx, js::AutoKeepTypeScripts&);
@@ -2084,6 +2089,12 @@ class JSScript : public js::gc::TenuredCell
     uint32_t stepModeCount() { return bitFields_.hasDebugScript_ ? debugScript()->stepMode : 0; }
 #endif
 
+    // Set/get a embedding pointer that can be associated with top-level (global
+    // or module) scripts. Note that although isTopLevel() can return true for
+    // eval scripts, these are not supported.
+    void setTopLevelPrivate(void* value);
+    void* maybeTopLevelPrivate() const;
+
     void finalize(js::FreeOp* fop);
 
     static const JS::TraceKind TraceKind = JS::TraceKind::Script;

js/src/vm/Scope.h

@@ -419,6 +419,17 @@ class Scope : public js::gc::TenuredCell
 class BaseScopeData
 {};
 
+/*
+ * Scope for a top level script: either a global (classic) script or a module
+ * script.
+ */
+class TopLevelScopeData : public BaseScopeData
+{
+  public:
+    // Private data for use by the embedding.
+    void* privateData = nullptr;
+};
+
 template<class Data>
 inline size_t
 SizeOfData(uint32_t numBindings)
@@ -772,7 +783,7 @@ class GlobalScope : public Scope
   public:
     // Data is public because it is created by the frontend. See
     // Parser<FullParseHandler>::newGlobalScopeData.
-    struct Data : BaseScopeData
+    struct Data : public TopLevelScopeData
     {
         // Bindings are sorted by kind.
         // `vars` includes top-level functions which is distinguished by a bit
@@ -826,6 +837,14 @@ class GlobalScope : public Scope
     bool hasBindings() const {
         return data().length > 0;
     }
+
+    void setTopLevelPrivate(void* value) {
+        data().privateData = value;
+    }
+
+    void* topLevelPrivate() const {
+        return data().privateData;
+    }
 };
 
 template <>
@@ -964,7 +983,7 @@ class ModuleScope : public Scope
   public:
     // Data is public because it is created by the frontend. See
     // Parser<FullParseHandler>::newModuleScopeData.
-    struct Data : BaseScopeData
+    struct Data : public TopLevelScopeData
     {
         // The module of the scope.
         GCPtr<ModuleObject*> module = {};
@@ -1021,6 +1040,14 @@ class ModuleScope : public Scope
 
     JSScript* script() const;
 
+    void setTopLevelPrivate(void* value) {
+        data().privateData = value;
+    }
+
+    void* topLevelPrivate() const {
+        return data().privateData;
+    }
+
     static Shape* getEmptyEnvironmentShape(JSContext* cx);
 };