Discussion WriteAllBytesAsync and ReadAllBytesAsync don't work with WebGL

Hey, if anything I want this post to show up when someone googles for this, because I had to find this out on my own.

For those who don't know, WebGL is single threaded - which means any multi-threaded resources won't work in it. A common example is the WebClient library, which should be replaced by the WebRequest library, and more.

That doesn't mean Async and Tasks in general aren't supported - because asyncronous task based programming isn't multi threaded - this is a common misconception.

That said, specifically the WriteAllBytesAsync and ReadAllBytesAsync don't work. This probably means they are multi threaded in their inner workings or there's some other reason I don't know (if someone does, I'm really curious to know)

This is how I've tested it:

Code (CSharp):

1. using System.IO;
2. using UnityEngine;
3.  
4. public class TestingWriteReadInWebGL : MonoBehaviour
5. {
6.  
7.     [SerializeField] private Texture2D tex;
8.    
9.     async void Start()
10.     {
11.         string path = Application.persistentDataPath + "/TestPic.png";
12.         Debug.Log("Writing to path/url: " + path);
13.         byte[] data = tex.GetRawTextureData();
14.         Debug.Log("Data: " + new string(System.Text.Encoding.UTF8.GetString(data).ToCharArray()));
15.         await File.WriteAllBytesAsync(path, data);
16.         Debug.Log("Tried writing to path/url: " + path);
17.         byte[] bytes = await File.ReadAllBytesAsync(path);
18.         Debug.Log("Read from path/url: " + path);
19.         Debug.Log("Data: " + new string(System.Text.Encoding.UTF8.GetString(bytes).ToCharArray()));
20.     }
21. }
22.  

Replace them with their non async counterparts and it works. So I guess we just gotta deal with it.

That's it