From 8f9343aab1e9ea809835e69cc1277c167946564c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Standa=20Luke=C5=A1?= <exyi@outlook.cz>
Date: Sun, 22 Oct 2023 15:32:04 +0200
Subject: [PATCH] Introduce DataContextStart.CreateCollectionElement

Creates a nested data context with _index and _collection extension parameters
---
 .../GeneralBindingPropertyResolvers.cs        |  5 ++---
 .../ControlTree/DataContextStack.cs           | 19 +++++++++++++++++++
 2 files changed, 21 insertions(+), 3 deletions(-)

diff --git a/src/Framework/Framework/Compilation/Binding/GeneralBindingPropertyResolvers.cs b/src/Framework/Framework/Compilation/Binding/GeneralBindingPropertyResolvers.cs
index e0ffccd615..e29eb171f0 100644
--- a/src/Framework/Framework/Compilation/Binding/GeneralBindingPropertyResolvers.cs
+++ b/src/Framework/Framework/Compilation/Binding/GeneralBindingPropertyResolvers.cs
@@ -427,10 +427,9 @@ public ThisBindingProperty GetThisBinding(IBinding binding, DataContextStack sta
 
         public CollectionElementDataContextBindingProperty GetCollectionElementDataContext(DataContextStack dataContext, ResultTypeBindingProperty resultType)
         {
-            return new CollectionElementDataContextBindingProperty(DataContextStack.Create(
+            return new CollectionElementDataContextBindingProperty(DataContextStack.CreateCollectionElement(
                 ReflectionUtils.GetEnumerableType(resultType.Type).NotNull(),
-                parent: dataContext,
-                extensionParameters: new CollectionElementDataContextChangeAttribute(0).GetExtensionParameters(new ResolvedTypeDescriptor(dataContext.DataContextType)).ToArray()
+                dataContext
             ));
         }
 
diff --git a/src/Framework/Framework/Compilation/ControlTree/DataContextStack.cs b/src/Framework/Framework/Compilation/ControlTree/DataContextStack.cs
index a655cadc35..f43a04f963 100644
--- a/src/Framework/Framework/Compilation/ControlTree/DataContextStack.cs
+++ b/src/Framework/Framework/Compilation/ControlTree/DataContextStack.cs
@@ -4,6 +4,7 @@
 using System.Collections.Immutable;
 using System.Linq;
 using System.Runtime.CompilerServices;
+using DotVVM.Framework.Binding;
 using DotVVM.Framework.Compilation.ControlTree.Resolved;
 using DotVVM.Framework.Utils;
 using FastExpressionCompiler;
@@ -172,5 +173,23 @@ public static DataContextStack Create(Type type,
             var dcs = new DataContextStack(type, parent, imports, extensionParameters, bindingPropertyResolvers);
             return dcs;// internCache.GetValue(dcs, _ => dcs);
         }
+
+
+        /// <summary> Creates a new data context level with _index and _collection extension parameters. </summary>
+        public static DataContextStack CreateCollectionElement(Type elementType,
+            DataContextStack? parent = null,
+            IReadOnlyList<NamespaceImport>? imports = null,
+            IReadOnlyList<BindingExtensionParameter>? extensionParameters = null,
+            IReadOnlyList<Delegate>? bindingPropertyResolvers = null)
+        {
+            var indexParameters = new CollectionElementDataContextChangeAttribute(0).GetExtensionParameters(new ResolvedTypeDescriptor(elementType.MakeArrayType()));
+            extensionParameters = extensionParameters is null ? indexParameters.ToArray() : extensionParameters.Concat(indexParameters).ToArray();
+            return DataContextStack.Create(
+                elementType, parent,
+                imports: imports,
+                extensionParameters: extensionParameters,
+                bindingPropertyResolvers: bindingPropertyResolvers
+            );
+        }
     }
 }