How to export JavaScript object that has Promise functions?

babayaga22 · April 30, 2020, 9:41am

I have a module that handles database pool creation. I created an export function to expose database pool for other fivem modules.

exports('getPool', () => {
    return pool;
});

Now I can access this pool from other resources, however this object has a method getConnection(), which returns connection via a JavaScript Promise API. When I call this method an empty object is returned to me in code.

const dbPool = exports["my-resource"].getPool(); // Object.keys(dbPool) has all functions
const conn = await dbPool.getConnection(); // <-- will be completely unrelated object where Object.keys(conn) === []

Of course it works when I will duplicate pool code in this resource, but this will cause a problem of having multiple database pools in runtime.

Maybe somebody has encountered similar problem and can help me.

nta · April 30, 2020, 10:46am

Not supported at this time. You could provide a PR that implements __cfx_async_retval support similar to C# and Lua have already.

(update in 2022 as people still find this post: implemented fine as of this PR feat(scripting/v8): Add support for __cfx_async_retval by dunak-debug · Pull Request #975 · citizenfx/fivem · GitHub)

babayaga22 · April 30, 2020, 10:54am

Can you link me to a GitHub project, so I could take a look? Thanks.

nta · April 30, 2020, 11:22am

github.com

citizenfx/fivem/blob/8def3a3a9625f4e3c59fb07840aeda2dbe157336/data/shared/citizen/scripting/v8/main.js

// CFX JS runtime
/// <reference path="./natives_blank.d.ts" />
/// <reference path="./natives_server.d.ts" />

const EXT_FUNCREF = 10;
const EXT_LOCALFUNCREF = 11;

(function (global) {
	let boundaryIdx = 1;
	let lastBoundaryStart = null;
	
	// temp
	global.FormatStackTrace = function(args, argLength) {
		return Citizen.invokeNativeByHash(0, 0xd70c3bca, args, argLength, Citizen.resultAsString());
	}
	
	function getBoundaryFunc(pushFunc, id) {
		return (func, ...args) => {
			const boundary = id || (boundaryIdx++);
			pushFunc(boundary);

This file has been truncated. show original

github.com

citizenfx/fivem/blob/8def3a3a9625f4e3c59fb07840aeda2dbe157336/data/shared/citizen/scripting/lua/scheduler.lua

local debug = debug

-- temp
local function FormatStackTrace()
	return Citizen.InvokeNative(`FORMAT_STACK_TRACE` & 0xFFFFFFFF, nil, 0, Citizen.ResultAsString())
end

local function ProfilerEnterScope(scopeName)
	return Citizen.InvokeNative(`PROFILER_ENTER_SCOPE` & 0xFFFFFFFF, scopeName)
end

local function ProfilerExitScope()
	return Citizen.InvokeNative(`PROFILER_EXIT_SCOPE` & 0xFFFFFFFF)
end

local newThreads = {}
local threads = setmetatable({}, {
	-- This circumvents undefined behaviour in "next" (and therefore "pairs")
	__newindex = newThreads,
	-- This is needed for CreateThreadNow to work correctly

This file has been truncated. show original

github.com

citizenfx/fivem/blob/1d0743f9d418de6260597df2ed67c0c42064c87d/code/client/clrcore/MsgPackDeserializer.cs#L278




				var returnData = Deserialize(returnByteData) as List<object>;



				if (returnData == null || returnData.Count == 0)

				{

					return null;

				}



				if (returnData[0] is IDictionary<string, object> obj)

				{

					if (obj.TryGetValue("__cfx_async_retval", out dynamic asyncRef))

					{

						var tcs = new TaskCompletionSource<object>();



						asyncRef(new Action<dynamic, dynamic>((res, err) =>

						{

							if (err != null && err != false)

							{

								tcs.SetException(new Exception(err.ToString()));

							}

							else

github.com

citizenfx/fivem/blob/8987679a4ea5d72fbdf90dc6ca24bba71937728f/code/client/clrcore/FunctionReference.cs#L67




            var method = funcRef.m_method;



            // deserialize the passed arguments

            var argList = (List<object>)MsgPackDeserializer.Deserialize(arguments);

            var argArray = CallUtilities.GetPassArguments(method.Method, argList.ToArray(), string.Empty);



			// the Lua runtime expects this to be an array, so it be an array.

			var rv = method.DynamicInvoke(argArray);



			// is this actually an asynchronous method?

			if (rv is Task)

			{

				dynamic rt = rv;



				rv = new

				{

					__cfx_async_retval = new Action<dynamic>(rvcb =>

					{

						rt.ContinueWith(new Action<Task>(t =>

						{

licccboeh · May 1, 2020, 12:16pm

How to build Linux artifacts out of fork?

I did look at gitlab-ci and “build_server_proot.sh” script, but there are some env variables like FIVEM_PRIVATE_URI, which I don’t seem to find any documentation on. Plan was to quickly spin up CI process and start testing the changes.

Unless, there is a better way to do it, which I haven’t found.

Thanks!

nta · May 1, 2020, 7:06pm

Just check what the .travis.yml does.

Christian_Moen · May 9, 2021, 3:21pm

There’s a PR here, that’s currently a draft… Any info on what’s missing in this to have it worth a merge?

babayaga22 · May 12, 2021, 12:36pm

No idea it’s not my pull request. I forked the repo in 2020 and tried modifying the engine (through trial & error) to support async & Promise, but I never got it working. My fork can be found here Commits · bound2/fivem · GitHub