Support the import.meta property

Through the `import.meta` property the engine can pass some values to
the module. Currently only the `path` of the script file is exposed.

source/scriptinterface/ModuleLoader.cpp

@@ -160,6 +160,10 @@ ModuleLoader::CompiledModule::CompiledModule(const ScriptRequest& rq, const VfsP
 		throw std::invalid_argument{fmt::format("Unable to compile module: \"{}\".",
 			filePathStr)};
 	}
+
+	JS::RootedValue modInfo{rq.cx};
+	Script::CreateObject(rq, &modInfo, "path", filePathStr);
+	JS::SetModulePrivate(m_ModuleObject, modInfo);
 }
 
 ModuleLoader::Future::Future(const ScriptRequest& rq, ModuleLoader& loader, const VfsPath& modulePath):
@@ -236,6 +240,26 @@ void ModuleLoader::Future::SetReservedSlot(JS::Value privateValue) noexcept
 	return Future{rq, *this, modulePath};
 }
 
+/**
+ * This is only executed once per module. Following accesses of `import.meta`
+ * evaluate to the same object.
+ */
+[[nodiscard]] bool ModuleLoader::MetadataHook(JSContext* cx, JS::HandleValue privateValue,
+	JS::HandleObject metaObject) noexcept
+{
+	const ScriptRequest rq{cx};
+
+	JS::RootedValue path{cx};
+	if (!Script::GetProperty(rq, privateValue, "path", &path))
+		return false;
+
+	JS::RootedValue metaValue{cx, JS::ObjectValue(*metaObject)};
+	if (!Script::SetProperty(rq, metaValue, "path", path))
+		return false;
+
+	return true;
+}
+
 [[nodiscard]] JSObject* ModuleLoader::ResolveHook(JSContext* cx, JS::HandleValue,
 	JS::HandleObject moduleRequest) noexcept
 {

source/scriptinterface/ModuleLoader.h

@@ -100,6 +100,8 @@ public:
 
 private:
 	// Functions used by the `ScriptContext`.
+	[[nodiscard]] static bool MetadataHook(JSContext* cx, JS::HandleValue privateValue,
+		JS::HandleObject metaObject) noexcept;
 	[[nodiscard]] static JSObject* ResolveHook(JSContext* cx, JS::HandleValue,
 		JS::HandleObject moduleRequest) noexcept;
 	[[nodiscard]] static bool DynamicImportHook(JSContext* cx, JS::HandleValue referencingPrivate,

source/scriptinterface/ScriptContext.cpp

@@ -155,6 +155,7 @@ ScriptContext::ScriptContext(int contextSize, uint32_t heapGrowthBytesGCTrigger)
 	JS::SetPromiseRejectionTrackerCallback(m_cx, &Script::UnhandledRejectedPromise);
 
 	JSRuntime* runtime{JS_GetRuntime(m_cx)};
+	JS::SetModuleMetadataHook(runtime, &Script::ModuleLoader::MetadataHook);
 	JS::SetModuleResolveHook(runtime, &Script::ModuleLoader::ResolveHook);
 	JS::SetModuleDynamicImportHook(runtime, &Script::ModuleLoader::DynamicImportHook);
 }
@@ -166,6 +167,7 @@ ScriptContext::~ScriptContext()
 	JSRuntime* runtime{JS_GetRuntime(m_cx)};
 	JS::SetModuleDynamicImportHook(runtime, nullptr);
 	JS::SetModuleResolveHook(runtime, nullptr);
+	JS::SetModuleMetadataHook(runtime, nullptr);
 
 	// Switch back to normal performance mode to avoid assertion in debug mode.
 	js::gc::SetPerformanceHint(m_cx, js::gc::PerformanceHint::Normal);

source/scriptinterface/tests/test_Module.h

@@ -401,4 +401,24 @@ public:
 		TS_ASSERT_LESS_THAN(pi, 3.1416);
 		TS_ASSERT_LESS_THAN(3.1415, pi);
 	}
+
+	void test_Meta()
+	{
+		ScriptInterface script{"Test", "Test", g_ScriptContext};
+		const ScriptRequest rq{script};
+
+		auto future = script.GetModuleLoader().LoadModule(rq, "meta.js");
+
+		g_ScriptContext->RunJobs();
+
+		JS::RootedObject ns{rq.cx, future.Get()};
+		const JS::RootedValue modNamespace{rq.cx, JS::ObjectValue(*ns)};
+
+		JS::RootedValue meta{rq.cx};
+		TS_ASSERT(ScriptFunction::Call(rq, modNamespace, "getMeta", &meta));
+
+		std::string path;
+		TS_ASSERT(Script::GetProperty(rq, meta, "path", path));
+		TS_ASSERT_STR_EQUALS(path, "meta.js");
+	}
 };