Proto.Promises.PromiseYieldExtensions exception on Android?

[drew-512]

I'm turning the corner on this forthcoming release (excited to show ya Tim!) and just recently have an Android build since a long period. I'm getting a 100% reproducible exception within PP:

Exception: Exception: Failed to read 'jar:file:///data/app/~~fvfP2-kEXeOGS9xNYiyy2w==/com.soundpspectrum.tunr--JUWMsMNG0Kq_1ryachGLQ==/base.apk!/assets/Bundled/app.vars.factory.json'
System.NullReferenceException: Object reference not set to an instance of an object.
  at Proto.Promises.PromiseYieldExtensions+AwaitInstructionAwaiter`1[TAwaitInstruction].OnCompleted (System.Action continuation) [0x00000] in <00000000000000000000000000000000>:0 
  at Proto.Promises.Internal+CriticalAwaitOverrider`1[TAwaiter].DefaultAwaitOnCompleted (TAwaiter& awaiter, Proto.Promises.Internal+PromiseRefBase asyncPromiseRef, System.Action continuation) [0x00000] in <00000000000000000000000000000000>:0 
  at Amp.App.ReadAllBytes (System.String absPath, System.Boolean suppressFNF) [0x00000] in <00000000000000000000000000000000>:0 
  at Amp.AssetService.loadTextureUsingWebRequest (Amp.AssetRequest assetReq) [0x00000] in <00000000000000000000000000000000>:0 
  at Amp.App.ReadAllBytes (System.String absPath, System.Boolean suppressFNF) [0x00000] in <00000000000000000000000000000000>:0 
  at Amp.App.ReadAllText (System.String absPath, System.Boolean suppressFNF) [0x00000] in <00000000000000000000000000000000>:0 
  at Amp.AssetService.loadTextureUsingWebRequest (Amp.AssetRequest assetReq) [0x00000] in <00000000000000000000000000000000>:0 
  at Amp.App.ReadAllText (System.String absPath, System.Boolean suppressFNF) [0x00000] in <00000000000000000000000000000000>:0 
  at Amp.App.readAppVars () [0x00000] in <00000000000000000000000000000000>:0 
  at Amp.AssetService.loadTextureUsingWebRequest (Amp.AssetRequest assetReq) [0x00000] in <00000000000000000000000000000000>:0 
  at Amp.App.readAppVars () [0x00000] in <00000000000000000000000000000000>:0 
  at Amp.App.OnApplicationStart () [0x00000] in <00000000000000000000000000000000>:0 
  at Amp.AssetService.loadTextureUsingWebRequest (Amp.AssetRequest assetReq) [0x00000] in <00000000000000000000000000000000>:0 
  at Amp.App.OnApplicationStart () [0x00000] in <00000000000000000000000000000000>:0 
  at Amp.App.Awake () [0x00000] in <00000000000000000000000000000000>:0 
  at System.Runtime.CompilerServices.AsyncVoidMethodBuilder.Start[TStateMachine] (TStateMachine& stateMachine) [0x00000] in <00000000000000000000000000000000>:0 
  at Amp.App.Awake () [0x00000] in <00000000000000000000000000000000>:0 

Offending function:

        public static async Promise<byte[]>     ReadAllBytes(string absPath, bool suppressFNF = false) {
            byte[] buf = null;
            string err = null;
            
            if (absPath.StartsWith("jar:file:")) {
                using (var req = UnityWebRequest.Get(absPath)) {
                    req.downloadHandler = new DownloadHandlerBuffer();
                    await PromiseYielder.WaitForAsyncOperation(req.SendWebRequest());  // << Exception 
                    ...
                }
            } else {
                ...
            }
            ...
            return buf;
        }

Before the switch to PP, the above function look like and was in production:

        public static async Task<byte[]>        ReadAllBytes(string absPath, bool suppressFNF = false) {
            byte[] buf = null;
            string err = null;
            
            if (absPath.StartsWith("jar:file:")) {
                using (var req = UnityWebRequest.Get(absPath)) {
                    req.downloadHandler = new DownloadHandlerBuffer();
                    await req.SendWebRequest();
                    ...
                }
            } else {
                ...
            }
            ...
            return buf;
        }

Looking at the stack trace, it's suspicious to see another async call loadTextureUsingWebRequest is unexpectedly interleaved and thinking I'm doing something fooling elsewhere? For reference, here's those other (unrelated but possibly concurrent) functions:

        AsyncSemaphore _maxFileLoads = new AsyncSemaphore(4);
        AsyncSemaphore _maxWebReqs   = new AsyncSemaphore(2);

        async void loadTextureFromFile(AssetRequest texReq, string pathname) {
            await Promise.SwitchToBackgroundAwait(true);
            
            byte[] texData = null;
            using (await _maxFileLoads.EnterScopeAsync()) {
                ...
                try {
                    texData = File.ReadAllBytes(pathname);
                } catch (Exception e) {
                    texReq.Fail($"failed to read file '{pathname}': {e.Message}");
                    return;
                }
            }
            
            await Promise.SwitchToForegroundAwait();

            Texture2D tex2D = new Texture2D(1,1);
            if (tex2D.LoadImage(texData)) {
                texReq.Resolve(tex2D);
            } else {
                Destroy(tex2D);
                texReq.Fail($"failed to load texture from file '{pathname}'");
            }
        }
        
        async void loadTextureUsingWebRequest(AssetRequest assetReq) {
            using (await _maxWebReqs.EnterScopeAsync()) {
                string url = assetReq.Get.URL;
                using (var req = UnityWebRequestTexture.GetTexture(url, false)) {
                    await PromiseYielder.WaitForAsyncOperation(req.SendWebRequest());
                    
                    if (req.result == UnityWebRequest.Result.Success) {
                        assetReq.Resolve(((DownloadHandlerTexture) req.downloadHandler).texture);
                    } else {
                        assetReq.Fail(req.error);
                    }
                }
            }
        }

[timcassell]

Are you able to reproduce in editor by chance? Or is it only happening on device?

[timcassell]

Also, at what point in the program is that running? Before Awake? Looking at the code, the only thing that could be null there is InternalHelper.PromiseBehaviour.Instance which gets initialized in [RuntimeInitializeOnLoadMethod(RuntimeInitializeLoadType.BeforeSceneLoad)], so if it's running before that it could break.

[drew-512]

I don't have the setup for a simulator and this is on my vanilla testing Android I'm using.

The call happens from Awake() on my root "App" MonoBehavior:

        
        async void                          Awake() {
            ...
            DontDestroyOnLoad(this.gameObject);
            await OnApplicationStart();
            ...
        }
        
    
        public async Promise                OnApplicationStart() {
            ...
            await readAppVars();
            ...
        }
        

[timcassell]

Does #513 fix it?

[drew-512]

Fix confirmed good to go, appreciate your diligence!

[timcassell]

Well, I found the actual cause. I create the PromiseBehaviour instance in BeforeSceneLoad, but I don't actually assign the s_instance field until Start. So your Awake is being ran before it. I'm surprised you didn't observe the same bug in editor. I don't remember the exact reason why I did that, probably some weird Unity quirk I was trying to work around.

So #513 was only a half-fix. I'm working on a comprehensive fix now.

[drew-512]

ah, ok great -- appreciate your efforts!