Implemented extensible way to deal with results of commands. This is …

src/DotVVM.Framework.PerfTests/SerializerTests.cs

@@ -56,7 +56,7 @@ public void Serialize()
         {
             viewModel.Nested.Array[0].MyProperty = Guid.NewGuid().ToString(); // modify a bit
 
-            serializer.BuildViewModel(request);
+            serializer.BuildViewModel(request, null);
             LastViewModel = serializer.SerializeViewModel(request);
             if (allowDiffs) request.ReceivedViewModelJson = (JObject)request.ViewModelJson["viewModel"];
         }

src/DotVVM.Framework/Hosting/DotvvmPresenter.cs

@@ -180,8 +180,8 @@ public async Task ProcessRequestCore(IDotvvmRequestContext context)
                 // run the init phase in the page
                 DotvvmControlCollection.InvokePageLifeCycleEventRecursive(page, LifeCycleEventType.Init);
                 await requestTracer.TraceEvent(RequestTracingConstants.InitCompleted, context);
-                object? commandResult = null;
 
+                object? commandResult = null;
                 if (!isPostBack)
                 {
                     // perform standard get
@@ -268,8 +268,7 @@ public async Task ProcessRequestCore(IDotvvmRequestContext context)
                 }
                 await requestTracer.TraceEvent(RequestTracingConstants.ViewModelSerialized, context);
 
-                ViewModelSerializer.BuildViewModel(context);
-                if (commandResult != null) context.ViewModelJson!["commandResult"] = JToken.FromObject(commandResult);
+                ViewModelSerializer.BuildViewModel(context, commandResult);
 
                 if (!context.IsInPartialRenderingMode)
                 {
@@ -373,7 +372,8 @@ public async Task ProcessStaticCommandRequest(IDotvvmRequestContext context)
 
                 var result = await ExecuteCommand(actionInfo, context, filters);
 
-                await OutputRenderer.WriteStaticCommandResponse(context,
+                await OutputRenderer.WriteStaticCommandResponse(
+                    context,
                     ViewModelSerializer.BuildStaticCommandResponse(context, result));
             }
             finally
@@ -393,17 +393,22 @@ await OutputRenderer.WriteStaticCommandResponse(context,
             }
 
             object? result = null;
-            Task? resultTask = null;
-
             try
             {
+                Task? resultTask = null;
+
                 result = action.Action();
 
                 resultTask = result as Task;
                 if (resultTask != null)
                 {
                     await resultTask;
                 }
+
+                if (resultTask != null)
+                {
+                    result = TaskUtils.GetResult(resultTask);
+                }
             }
             catch (Exception ex)
             {
@@ -428,12 +433,6 @@ await OutputRenderer.WriteStaticCommandResponse(context,
             {
                 throw new Exception("Unhandled exception occurred in the command!", context.CommandException);
             }
-
-            if (resultTask != null)
-            {
-                return TaskUtils.GetResult(resultTask);
-            }
-
             return result;
         }
 

src/DotVVM.Framework/Hosting/DotvvmRequestContext.cs

@@ -110,6 +110,7 @@ public class DotvvmRequestContext : IDotvvmRequestContext
         public IViewModelSerializer ViewModelSerializer => Services.GetRequiredService<IViewModelSerializer>();
 
         private IServiceProvider? _services;
+
         public IServiceProvider Services
         {
             get => _services ?? (_services = Configuration.ServiceProvider ?? throw new NotSupportedException());
@@ -118,6 +119,8 @@ public IServiceProvider Services
 
         public IHttpContext HttpContext { get; set; }
 
+        private readonly Dictionary<string, object> customResponseProperties = new Dictionary<string, object>();
+        public IReadOnlyDictionary<string, object> CustomResponseProperties => customResponseProperties;
         public DotvvmRequestContext(
             IHttpContext httpContext,
             DotvvmConfiguration configuration,
@@ -136,5 +139,14 @@ public static DotvvmRequestContext GetCurrent(IHttpContext httpContext)
             return httpContext.GetItem<DotvvmRequestContext>(HostingConstants.DotvvmRequestContextOwinKey)
                    .NotNull();
         }
+
+        public void AddCustomResponseProperty(string key, object value)
+        {
+            if(customResponseProperties.ContainsKey(key))
+            {
+                throw new InvalidOperationException($"Custom property {key} already exists.");
+            }
+            customResponseProperties[key] = value;
+        }
     }
 }

src/DotVVM.Framework/Hosting/IDotvvmRequestContext.cs

@@ -111,5 +111,7 @@ public interface IDotvvmRequestContext
         string? ResultIdFragment { get; set; }
 
         IServiceProvider Services { get; }
+        IReadOnlyDictionary<string, object> CustomResponseProperties { get; }
+        void AddCustomResponseProperty(string key, object value);
     }
 }

src/DotVVM.Framework/Resources/Scripts/global-declarations.ts

@@ -145,6 +145,7 @@ interface DotvvmPostbackHandlerCollection {
 
 type DotvvmStaticCommandResponse = {
     result: any;
+    customData: { [key: string]: any };
 } | {
     action: "redirect";
     url: string;

src/DotVVM.Framework/Resources/Scripts/postback/postback.ts

@@ -68,7 +68,7 @@ export async function postBack(
                 serverResponseObject,
                 wasInterrupted,
                 commandResult: null,
-                response: (err.reason as any).response,
+                response: (err.reason as any)?.response,
                 error: err
             }
             events.afterPostback.trigger(eventArgs);
@@ -78,7 +78,7 @@ export async function postBack(
                 const errorEventArgs: DotvvmErrorEventArgs = {
                     ...options,
                     serverResponseObject,
-                    response: (err.reason as any).response,
+                    response: (err.reason as any)?.response,
                     error: err,
                     handled: false
                 }
@@ -89,7 +89,7 @@ export async function postBack(
                     return {
                         ...options,
                         serverResponseObject,
-                        response: (err.reason as any).response,
+                        response: (err.reason as any)?.response,
                         error: err
                     };
                 }
@@ -153,7 +153,7 @@ export async function applyPostbackHandlers(
                 const errorEventArgs: DotvvmErrorEventArgs = {
                     ...options,
                     serverResponseObject,
-                    response: (err.reason as any).response,
+                    response: (err.reason as any)?.response,
                     error: err,
                     handled: false
                 }
@@ -165,7 +165,7 @@ export async function applyPostbackHandlers(
                     return {
                         ...options,
                         serverResponseObject,
-                        response: (err.reason as any).response,
+                        response: (err.reason as any)?.response,
                         error: err
                     };
                 }
@@ -282,6 +282,7 @@ function shouldTriggerErrorEvent(err: DotvvmPostbackError) {
     return err.reason.type == "network" || err.reason.type == "serverError";
 }
 function extractServerResponseObject(err: DotvvmPostbackError) {
+    if (!err.reason) return null;
     if (err.reason.type == "commit" && err.reason.args) {
         return err.reason.args.serverResponseObject;
     } 
@@ -291,4 +292,4 @@ function extractServerResponseObject(err: DotvvmPostbackError) {
         return err.reason.responseObject;
     }
     return null;
-}
+}

src/DotVVM.Framework/Resources/Scripts/postback/postbackCore.ts

@@ -208,4 +208,5 @@ type PostbackResponse =
         commandResult: any
         action: string
         resultIdFragment?: string
+        customData?: { [key: string]: any }
     }

src/DotVVM.Framework/Resources/Scripts/postback/staticCommand.ts

@@ -56,8 +56,8 @@ export async function staticCommandPostback(sender: HTMLElement, command: string
             methodId: command,
             methodArgs: args,
             error: err,
-            result: (err.reason as any).responseObject, 
-            response: (err.reason as any).response 
+            result: (err.reason as any)?.responseObject, 
+            response: (err.reason as any)?.response 
         })
 
         throw err;

src/DotVVM.Framework/Testing/TestDotvvmRequestContext.cs

@@ -39,10 +39,22 @@ public class TestDotvvmRequestContext : IDotvvmRequestContext
         public DotvvmView View { get; set; }
 
         private IServiceProvider _services;
+
         public IServiceProvider Services
         {
             get => _services ?? Configuration?.ServiceProvider ?? throw new NotSupportedException();
             set => _services = value;
         }
+
+        private readonly Dictionary<string, object> customResponseProperties = new Dictionary<string, object>();
+        public IReadOnlyDictionary<string, object> CustomResponseProperties => customResponseProperties;
+        public void AddCustomResponseProperty(string key, object value)
+        {
+            if (customResponseProperties.ContainsKey(key))
+            {
+                throw new InvalidOperationException($"Custom property {key} already exists.");
+            }
+            customResponseProperties[key] = value;
+        }
     }
 }

src/DotVVM.Framework/ViewModel/Serialization/DefaultViewModelSerializer.cs

@@ -59,7 +59,7 @@ public string SerializeViewModel(IDotvvmRequestContext context)
         /// <summary>
         /// Builds the view model for the client.
         /// </summary>
-        public void BuildViewModel(IDotvvmRequestContext context)
+        public void BuildViewModel(IDotvvmRequestContext context, object commandResult)
         {
             // serialize the ViewModel
             var serializer = CreateJsonSerializer();
@@ -121,6 +121,9 @@ public void BuildViewModel(IDotvvmRequestContext context)
             }
             // TODO: do not send on postbacks
             if (validationRules?.Count > 0) result["validationRules"] = validationRules;
+
+            if (commandResult != null) result["commandResult"] = WriteCommandData(commandResult, serializer, "result");
+            AddCustomPropertiesIfAny(context, serializer, result);
 
             context.ViewModelJson = result;
         }
@@ -140,18 +143,33 @@ public string BuildStaticCommandResponse(IDotvvmRequestContext context, object r
                 UsedSerializationMaps = new HashSet<ViewModelSerializationMap>()
             };
             serializer.Converters.Add(viewModelConverter);
-            var writer = new JTokenWriter();
             var response = new JObject();
+            response["result"] = WriteCommandData(result, serializer, "result");
+            AddCustomPropertiesIfAny(context, serializer, response);
+            return response.ToString(JsonFormatting);
+        }
+
+        private static void AddCustomPropertiesIfAny(IDotvvmRequestContext context, JsonSerializer serializer, JObject response)
+        {
+            if (context.CustomResponseProperties != null && context.CustomResponseProperties.Count > 0)
+            {
+                response["customProperties"] = WriteCommandData(context.CustomResponseProperties, serializer, "custom properties");
+            }
+        }
+
+        private static JToken WriteCommandData(object data, JsonSerializer serializer, string description)
+        {
+            var writer = new JTokenWriter();
             try
             {
-                serializer.Serialize(writer, result);
+                serializer.Serialize(writer, data);
             }
             catch (Exception ex)
             {
-                throw new Exception($"Could not serialize viewModel of type { context.ViewModel.GetType().Name }. Serialization failed at property { writer.Path }. {GeneralViewModelRecommendations}", ex);
+                throw new Exception($"Could not serialize static command {description} of type '{ data.GetType().FullName}'. Serialization failed at property { writer.Path }. {GeneralViewModelRecommendations}", ex);
             }
-            response["result"] = writer.Token;
-            return response.ToString(JsonFormatting);
+
+            return writer.Token;
         }
 
         protected virtual JsonSerializer CreateJsonSerializer() => DefaultSerializerSettingsProvider.Instance.Settings.Apply(JsonSerializer.Create);

src/DotVVM.Framework/ViewModel/Serialization/IViewModelSerializer.cs

@@ -7,9 +7,9 @@ namespace DotVVM.Framework.ViewModel.Serialization
 {
     public interface IViewModelSerializer
     {
-        void BuildViewModel(IDotvvmRequestContext context);
+        void BuildViewModel(IDotvvmRequestContext context, object commandResult);
 
-        string BuildStaticCommandResponse(IDotvvmRequestContext context, object result);
+        string BuildStaticCommandResponse(IDotvvmRequestContext context, object commandResult);
 
         string SerializeViewModel(IDotvvmRequestContext context);
 

src/DotVVM.Samples.Common/DotVVM.Samples.Common.csproj

@@ -60,6 +60,7 @@
     <None Remove="Views\FeatureSamples\Resources\LocationFallback.dothtml" />
     <None Remove="Views\FeatureSamples\Resources\RequiredOnPostback.dothtml" />
     <None Remove="Views\FeatureSamples\Serialization\DeserializationVirtualElements.dothtml" />
+    <None Remove="Views\FeatureSamples\CustomResponseProperties\SimpleExceptionFilter.dothtml" />
     <None Remove="Views\FeatureSamples\StaticCommand\StaticCommand_ArrayAssigment.dothtml" />
     <None Remove="Views\FeatureSamples\StaticCommand\StaticCommand_LoadComplexDataFromService.dothtml" />
     <None Remove="Views\FeatureSamples\StaticCommand\StaticCommand_NullAssignment.dothtml" />

src/DotVVM.Samples.Common/ViewModels/FeatureSamples/CustomResponseProperties/SimpleExceptionFilterViewModel.cs

@@ -0,0 +1,54 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using DotVVM.Framework.Hosting;
+using DotVVM.Framework.Runtime.Filters;
+using DotVVM.Framework.ViewModel;
+
+namespace DotVVM.Samples.Common.ViewModels.FeatureSamples.CustomResponseProperties
+{
+    public class PageErrorModel
+    {
+        public string Message { get; set; }
+    }
+    public class ClientExceptionFilterAttribute : ExceptionFilterAttribute
+    {
+        protected override Task OnCommandExceptionAsync(IDotvvmRequestContext context, ActionInfo actionInfo, Exception exception)
+        {
+            if (exception is UIException clientError)
+            {
+                context.AddCustomResponseProperty("validation-errors",new PageErrorModel {
+                    Message = clientError.Message
+                });
+                context.AddCustomResponseProperty("Message", "Hello there");
+
+                context.IsCommandExceptionHandled = true;
+            }
+            return Task.FromResult(0);
+        }
+    }
+    public class UIException : Exception
+    {
+        public UIException(string message) : base(message)
+        {
+        }
+    }
+    public class SimpleExceptionFilterViewModel : DotvvmViewModelBase
+    {
+        [AllowStaticCommand]
+        [ClientExceptionFilter]
+        public static void StaticCommand()
+        {
+            throw new UIException("Problem!");
+        }
+
+        [ClientExceptionFilter]
+        public void Command()
+        {
+            throw new UIException("Problem!");
+        }
+    }
+}
+

src/DotVVM.Samples.Common/Views/FeatureSamples/CustomResponseProperties/SimpleExceptionFilter.dothtml

@@ -0,0 +1,33 @@
+@viewModel DotVVM.Samples.Common.ViewModels.FeatureSamples.CustomResponseProperties.SimpleExceptionFilterViewModel, DotVVM.Samples.Common
+@import model = DotVVM.Samples.Common.ViewModels.FeatureSamples.CustomResponseProperties.SimpleExceptionFilterViewModel
+
+<html>
+<head>
+</head>
+<body>
+    <div>
+        <dot:Button Click="{staticCommand: model.StaticCommand()}" data-ui="staticCommand" Text="Static Command Test" />
+        <dot:Button Click="{command: Command()}" Text="Command Test"  data-ui="command" />
+        <dot:Button onclick="javascript: clearTexts()" Text="Clear" data-ui="clear"></dot:Button>
+    </div>
+    <p>
+        <span data-ui="customProperties"></span><br />
+    </p>
+    <dot:InlineScript>
+        function clearTexts(){
+            var customProperties = document.querySelector('[data-ui="customProperties"]');
+            customProperties.innerText = "";
+        }
+        dotvvm.events.staticCommandMethodInvoked.subscribe(e => {
+            var customPropertiesInput = document.querySelector('[data-ui="customProperties"]');
+            customPropertiesInput.innerText = e.serverResponseObject.customProperties.Message;
+        });
+
+        dotvvm.events.postbackResponseReceived.subscribe(e => {
+            var customPropertiesInput = document.querySelector('[data-ui="customProperties"]');
+            customPropertiesInput.innerText = e.serverResponseObject.customProperties.Message;
+        });
+    </dot:InlineScript>
+</body>
+</html>
+