Support PostBack.Handlers in CompositeControls

src/Framework/Framework/Compilation/ControlPrecompilationVisitor.cs

@@ -164,7 +164,10 @@ void checkProperty(IControlAttributeDescriptor property, Type targetType)
             var content = runtimeControl.ExecuteGetContents(null!);
 
             var config = services.GetService<DotvvmConfiguration>();
-            return content.Select(c => ResolvedControlHelper.FromRuntimeControl(c, control.DataContextTypeStack, config)).ToArray();
+            return content.Select(c => {
+                runtimeControl.CopyPostBackHandlersRecursive(c);
+                return ResolvedControlHelper.FromRuntimeControl(c, control.DataContextTypeStack, config);
+            }).ToArray();
         }
 
         /// Returns true if we can send binding into the property without evaluating it

src/Framework/Framework/Controls/CompositeControl.cs

@@ -13,6 +13,9 @@
 using DotVVM.Framework.Utils;
 using DotVVM.Framework.Compilation;
 using FastExpressionCompiler;
+using DotVVM.Framework.Compilation.Directives;
+using System.Windows.Input;
+using System.Diagnostics.Tracing;
 
 namespace DotVVM.Framework.Controls
 {
@@ -128,6 +131,106 @@ internal IEnumerable<DotvvmControl> ExecuteGetContents(IDotvvmRequestContext con
                 return Array.Empty<DotvvmControl>();
         }
 
+        /// <summary> Copies postback handlers onto controls with copied command bindings from this control.
+        /// Then adds those control into the Children collection (we have to this in one iteration to avoid enumerating the IEnumerable twice) </summary>
+        private void CopyPostbackHandlersAndAdd(IEnumerable<DotvvmControl> childControls)
+        {
+            if (this.GetValue(PostBack.HandlersProperty) is not PostBackHandlerCollection handlers || handlers.Count == 0)
+            {
+                foreach (var child in childControls)
+                    this.Children.Add(child);
+                return;
+            }
+
+            var commands = new List<(string, ICommandBinding)>();
+            foreach (var (property, value) in this.Properties)
+            {
+                if (value is ICommandBinding command)
+                    commands.Add((property.Name, command));
+            }
+
+            foreach (var child in childControls)
+            {
+                CopyPostBackHandlersRecursive(handlers, commands, child);
+                this.Children.Add(child);
+            }
+
+        }
+
+        /// <summary>
+        /// Copies postback handlers declared on the CompositeControl to the target child control, its children and properties recursively (including CloneTemplate, but not other ITemplate implementations).
+        /// Only postback handlers with a matching command binding are copied - Note that you have to set the command bindings before calling this method.
+        /// DotVVM copies the postback handlers automatically onto all controls returned from the GetContents method, but you might need to call this method to copy the handlers onto controls inside DelegateTemplate
+        /// </summary>
+        protected internal T CopyPostBackHandlersRecursive<T>(T target)
+            where T: DotvvmBindableObject
+        {
+            if (this.GetValue(PostBack.HandlersProperty) is not PostBackHandlerCollection handlers || handlers.Count == 0)
+                return target;
+
+            var commands = new List<(string, ICommandBinding)>();
+            foreach (var (property, value) in this.Properties)
+            {
+                if (value is ICommandBinding command)
+                    commands.Add((property.Name, command));
+            }
+            CopyPostBackHandlersRecursive(handlers, commands, target);
+
+            return target;
+        }
+
+        private static void CopyPostBackHandlersRecursive(PostBackHandlerCollection handlers, List<(string, ICommandBinding)> commands, DotvvmBindableObject target)
+        {
+            PostBackHandlerCollection? childHandlers = null;
+            foreach (var (property, value) in target.Properties)
+            {
+                if (value is ICommandBinding command)
+                {
+                    foreach (var (oldName, matchedCommand) in commands)
+                    {
+                        if (object.ReferenceEquals(command, matchedCommand))
+                        {
+                            CopyMatchingPostBackHandlers(handlers, oldName, property.Name, ref childHandlers);
+                            break;
+                        }
+                    }
+                }
+                else if (value is CloneTemplate template)
+                {
+                    foreach (var c in template.Controls)
+                    {
+                        CopyPostBackHandlersRecursive(handlers, commands, c);
+                    }
+                }
+                else if (value is DotvvmBindableObject child)
+                {
+                    CopyPostBackHandlersRecursive(handlers, commands, child);
+                }
+            }
+            if (childHandlers is { })
+                target.SetValue(PostBack.HandlersProperty, childHandlers);
+
+            if (target is DotvvmControl targetControl)
+                foreach (var c in targetControl.Children)
+                {
+                    CopyPostBackHandlersRecursive(handlers, commands, c);
+                }
+        }
+        static void CopyMatchingPostBackHandlers(PostBackHandlerCollection handlers, string oldName, string newName, ref PostBackHandlerCollection? newHandlers)
+        {
+            foreach (var h in handlers)
+            {
+                var name = h.EventName;
+                if (name == oldName || name is null)
+                {
+                    var newHandler = (PostBackHandler)h.CloneControl();
+                    newHandler.EventName = newName;
+                    newHandlers ??= new();
+                    newHandlers.Add(newHandler);
+                }
+            }
+        }
+
         protected internal override void OnLoad(IDotvvmRequestContext context)
         {
             if (!this.HasOnlyWhiteSpaceContent())
@@ -140,8 +243,7 @@ protected internal override void OnLoad(IDotvvmRequestContext context)
             if (this.Children.Count > 0)
                 throw new DotvvmControlException(this, $"{GetType().Name}.GetContents may not modify the Children collection, it should return the new children and it will be handled automatically.");
 
-            foreach (var child in content)
-                this.Children.Add(child);
+            CopyPostbackHandlersAndAdd(content);
 
             base.OnLoad(context);
         }

src/Tests/ControlTests/CompositeControlTests.cs

@@ -131,6 +131,8 @@ public async Task BindingMapping()
             check.CheckString(r.FormattedHtml, fileExtension: "html");
         }
 
+
+        [TestMethod]
         public async Task CommandDataContextChange()
         {
             // RepeatedButton2 creates button in repeater, but also 
@@ -151,6 +153,34 @@ public async Task CommandDataContextChange()
             Assert.AreEqual(15, (int)r.ViewModel.@int);
         }
 
+        [TestMethod]
+        public async Task AutoclonedPostbackHandlers()
+        {
+            var r = await cth.RunPage(typeof(BasicTestViewModel), """
+                <!-- command -->
+                <cc:RepeatedButton2 DataSource={value: List}
+                                    ItemClick={command: Integer = 15}
+                                    Precompile=false>
+                    <PostBack.Handlers>
+                        <dot:ConfirmPostBackHandler Message='Test not precompiled' />
+                    </PostBack.Handlers>
+                </cc:RepeatedButton2>
+                <cc:RepeatedButton2 DataSource={value: List}
+                                    ItemClick={command: Integer = 15}
+                                    Precompile=true>
+                    <PostBack.Handlers>
+                        <dot:ConfirmPostBackHandler Message='Test precompiled' />
+                    </PostBack.Handlers>
+                </cc:RepeatedButton2>
+                """
+            );
+
+            check.CheckString(r.FormattedHtml, fileExtension: "html");
+
+            XAssert.Contains("Test not precompiled", r.OutputString);
+            XAssert.Contains("Test precompiled", r.OutputString);
+        }
+
         [TestMethod]
         public async Task MarkupControlCreatedFromCodeControl()
         {
@@ -394,15 +424,20 @@ public static DotvvmControl GetContents(
         }
     }
 
-    [ControlMarkupOptions(Precompile = ControlPrecompilationMode.Always)]
+    [ControlMarkupOptions(Precompile = ControlPrecompilationMode.IfPossible)]
     public class RepeatedButton2: CompositeControl
     {
-        public static DotvvmControl GetContents(
+        public DotvvmControl GetContents(
             IValueBinding<IEnumerable<string>> dataSource,
 
-            ICommandBinding itemClick = null
+            ICommandBinding itemClick = null,
+            bool precompile = true
         )
         {
+            if (!precompile && this.GetValue(Internal.RequestContextProperty) is null)
+            {
+                throw new SkipPrecompilationException();
+            }
             // Places itemClick in two different data contexts
             var repeater = new Repeater() {
                 RenderAsNamedTemplate = false,

src/Tests/ControlTests/testoutputs/CompositeControlTests.AutoclonedPostbackHandlers.html

@@ -0,0 +1,19 @@
+<html>
+	<head></head>
+	<body>
+
+		<!-- command -->
+		<div>
+			<div data-bind="foreach: { data: List }">
+				<input onclick="dotvvm.postBack(this,[&quot;List/[$index]&quot;],&quot;IYZcgJXAUDcvRzk7&quot;,&quot;&quot;,ko.contextFor(this).$parentContext,[[&quot;confirm&quot;,{message:&quot;Test not precompiled&quot;}]],[],undefined).catch(dotvvm.log.logPostBackScriptError);event.stopPropagation();return false;" type="button" value="Item">
+			</div>
+			<input onclick="dotvvm.postBack(this,[],&quot;IYZcgJXAUDcvRzk7&quot;,&quot;&quot;,null,[[&quot;confirm&quot;,{message:&quot;Test not precompiled&quot;}]],[],undefined).catch(dotvvm.log.logPostBackScriptError);event.stopPropagation();return false;" type="button" value="Last Item">
+		</div>
+		<div>
+			<div data-bind="foreach: { data: List }">
+				<input onclick="dotvvm.postBack(this,[&quot;List/[$index]&quot;],&quot;/cYhsuIE/4DfszAC&quot;,&quot;&quot;,ko.contextFor(this).$parentContext,[[&quot;confirm&quot;,{message:&quot;Test precompiled&quot;}]],[],undefined).catch(dotvvm.log.logPostBackScriptError);event.stopPropagation();return false;" type="button" value="Item">
+			</div>
+			<input onclick="dotvvm.postBack(this,[],&quot;/cYhsuIE/4DfszAC&quot;,&quot;&quot;,null,[[&quot;confirm&quot;,{message:&quot;Test precompiled&quot;}]],[],undefined).catch(dotvvm.log.logPostBackScriptError);event.stopPropagation();return false;" type="button" value="Last Item">
+		</div>
+	</body>
+</html>

src/Tests/ControlTests/testoutputs/CompositeControlTests.CommandDataContextChange.html

@@ -4,18 +4,22 @@
 
 		<!-- command -->
 		<div>
-			<div data-bind="foreach: { &quot;data&quot;: List }">
+			<div data-bind="foreach: { data: List }">
 				<input onclick="dotvvm.postBack(this,[&quot;List/[$index]&quot;],&quot;IYZcgJXAUDcvRzk7&quot;,&quot;&quot;,ko.contextFor(this).$parentContext,[],[],undefined).catch(dotvvm.log.logPostBackScriptError);event.stopPropagation();return false;" type="button" value="Item">
 			</div>
 			<input onclick="dotvvm.postBack(this,[],&quot;IYZcgJXAUDcvRzk7&quot;,&quot;&quot;,null,[],[],undefined).catch(dotvvm.log.logPostBackScriptError);event.stopPropagation();return false;" type="button" value="Last Item">
 		</div>
 
 		<!-- staticCommand -->
 		<div>
-			<div data-bind="foreach: { &quot;data&quot;: List }">
-				<input onclick="dotvvm.applyPostbackHandlers((options) => options.knockoutContext.$parent.int(12).int(),this).catch(dotvvm.log.logPostBackScriptError);event.stopPropagation();return false;" type="button" value="Item">
+			<div data-bind="foreach: { data: List }">
+				<input onclick="dotvvm.applyPostbackHandlers((options) => {
+	options.knockoutContext.$parent.int(12);
+},this).catch(dotvvm.log.logPostBackScriptError);event.stopPropagation();return false;" type="button" value="Item">
 			</div>
-			<input onclick="dotvvm.applyPostbackHandlers((options) => options.viewModel.int(12).int(),this).catch(dotvvm.log.logPostBackScriptError);event.stopPropagation();return false;" type="button" value="Last Item">
+			<input onclick="dotvvm.applyPostbackHandlers((options) => {
+	options.viewModel.int(12);
+},this).catch(dotvvm.log.logPostBackScriptError);event.stopPropagation();return false;" type="button" value="Last Item">
 		</div>
 	</body>
 </html>