how to call a js function in another js engine safely

[Zaitonn]

now I need to call a function in another js engine in order to create more features for my application

here is my way but maybe there are some errors i think :(

flowchart TD
e1("engine1(JS1)")
e2("engine2(JS2)")
e3("engine3(JS3)")

e1-- export functions -->e2
e1-- export functions -->e3

c1["lock engine1 to call functions which are exported from it in c#"]
e2 --> c1
e3 --> c1
c2["return values to engine2/3"]

c1--->c2

Loading

• C#

  /// <summary>
  /// call the specified function with some arguments
  /// </summary>
  /// <returns>result</returns>
  public static JsValue SafeCall(JsValue func, params JsValue[] arguments)
  {
      if (func is not FunctionInstance functionInstance)
      {
          return JsValue.Undefined;
      }
      Engine engine = functionInstance.Engine;
      bool lockTaken = false;
      Monitor.TryEnter(engine, 1000, ref lockTaken);
      if (!lockTaken)
      {
          throw new TimeoutException();
      }
      try
      {
          return engine.Invoke(functionInstance, arguments);
      }
      finally
      {
          Monitor.Exit(engine);
      }
  }

• Engine1

  function regCommand(handler) {
      // some checking and handling
      return false; // or true
      // in a word, this function will return a boolean value
  }
  
  serein.exports('CHregCommand', regCommand);
  
  // some indifferent codes are hidden XD

• Engine2

  const CHregCommand = serein.imports('CHregCommand');
  
  const handler = {
      name: 'test1',
      triggers:[]
  }
  serein.log(serein.safeCall(CHregCommand, handler))

• Engine3

  const CHregCommand = serein.imports('CHregCommand');
  
  const handler = {
      name: 'test2', // the name is different
      triggers:[]
  }
  serein.log(serein.safeCall(CHregCommand, handler))

serein.exports and serein.imports may not be important. they two only set/get value from a Dictionary<string, JsValue>

i expect that the two engine(2/3) should correctly call the function CHregCommand from engine 1 and get an output of boolean value
but actually it seems that only one of the two can call it but without the output.

I have tried single-step debugging in C#, and it turned out that the code is stuck at line return engine.Invoke(functionInstance, arguments);. I guess SafeCall hasn't returned yet because the code in finally hasn't been executed. and this results that the another engine couldn't access to engine1 and then it threw TimeoutException

are there any mistakes? :(( i have been puzzled at it for days
or are there some alternative ways to reach the purpose?

---

if i remove Monitor.TryEnter(engine, 1000, ref lockTaken); and related checks, it can return correctly.

---

jint: 3.0.0-beta-2048
net: tested in net472 and net6.0-windows
os: windows 10

[Zaitonn]

20230606102749.mp4

[Genteure]

This file does not seems to be playable.

[Zaitonn]

try downloading?
i can play it on my phone

下载试试？（如果放不了我等下重新传一下

[Zaitonn]

2023-06-06.15-09-08.mp4

[Genteure]

Would you benefit from having multiple instances of Engine? If single thread performance is acceptable, having only one Engine would greatly reduce the complexity.

If multiple instances are necessary, I would recommend writing the "bridge" between Engines purely with C# primitive types and strings. Every "Jint object" holds a reference to their "owning" Engine, and creates other objects from that Engine. I could be wrong but I don't think mixing multiple Engines together is a good idea or even a supported use case, you would have a bird nest mesh of objects coming from different Engines mixed together.

Checkout Worker API for inspirations on implementing APIs that passes data between scripting contexts, specifically postMessage() method and message event. Another keyword to search for is "message bus" or "event bus".
You could then optionally write some wrappers based on the above postMessage API to achieve something similar to what you designed right now.
Depending on your use case you could also make a synchronous version of the "postMessage API" that returns the result with the same call, if that's simpler to you.

P.S. The video does play in VLC, but I still can't figure out what's happening.
P.S. 2: I don't have the time to run the code and debug right now, the above recommendation is based on the assumption of mixing multiple Engines is the root cause.

[Zaitonn]

Would you benefit from having multiple instances of Engine?

I use multiple instances of Engine to provide every plugin with a separate environment. Otherwise, there might be some code conflicts when running

thanks for your help very much !! I'll try it later:D

[Genteure]

Modules also provides some degree of separation.

[Zaitonn]

Modules also provide some degree of separation.

thanks for your inspiration!!