Limit content item recursions to 20

src/OrchardCore.Modules/OrchardCore.Contents/Liquid/BuildDisplayFilter.cs

@@ -14,6 +14,8 @@ namespace OrchardCore.Contents.Liquid
 {
     public class BuildDisplayFilter : ILiquidFilter
     {
+        private const int DefaultMaxContentItemRecursions = 20;
+
         public ValueTask<FluidValue> ProcessAsync(FluidValue input, FilterArguments arguments, TemplateContext ctx)
         {
             static async ValueTask<FluidValue> Awaited(Task<IShape> task)
@@ -49,8 +51,11 @@ static async ValueTask<FluidValue> Awaited(Task<IShape> task)
 
             var buildDisplayRecursionHelper = serviceProvider.GetRequiredService<IContentItemRecursionHelper<BuildDisplayFilter>>();
 
-            // When {{ Model.ContentItem | shape_build_display | shape_render }} is called prevent recursion.
-            if (buildDisplayRecursionHelper.IsRecursive(contentItem))
+            // When {{ Model.ContentItem | shape_build_display | shape_render }} is called prevent unlimited recursions.
+            // max_recursions is an optional argument to override the default limit of 20.
+            var maxRecursions = arguments["max_recursions"];
+            var recursionLimit = maxRecursions.Type == FluidValues.Number ? Convert.ToInt32(maxRecursions.ToNumberValue()) : DefaultMaxContentItemRecursions;
+            if (buildDisplayRecursionHelper.IsRecursive(contentItem, recursionLimit))
             {
                 return new ValueTask<FluidValue>(NilValue.Instance);
             }

src/OrchardCore.Modules/OrchardCore.Contents/Liquid/ContentItemRecursionHelper.cs

@@ -13,24 +13,35 @@ public interface IContentItemRecursionHelper<T> where T : ILiquidFilter
         /// <summary>
         /// Returns <see langword="True"/> when the <see cref="ContentItem"/> has already been evaluated during this request by the particular filter./>
         /// </summary>
-        bool IsRecursive(ContentItem contentItem);
+        bool IsRecursive(ContentItem contentItem, int maxRecursions = 1);
     }
 
     /// <inheritdocs />
     public class ContentItemRecursionHelper<T> : IContentItemRecursionHelper<T> where T : ILiquidFilter
     {
-        private HashSet<string> _contentItemIds = new HashSet<string>(StringComparer.OrdinalIgnoreCase);
+        private Dictionary<ContentItem, int> _recursions = new Dictionary<ContentItem, int>();
 
         /// <inheritdocs />
-        public bool IsRecursive(ContentItem contentItem)
+        public bool IsRecursive(ContentItem contentItem, int maxRecursions = 1)
         {
-            if (_contentItemIds.Contains(contentItem.ContentItemId))
+            if (_recursions.ContainsKey(contentItem))
             {
-                return true;
-            }
+                var counter = _recursions[contentItem];
+                if (maxRecursions < 1)
+                {
+                    maxRecursions = 1;
+                }
+
+                if (counter > maxRecursions)
+                {
+                    return true;
+                }
 
-            _contentItemIds.Add(contentItem.ContentItemId);
+                _recursions[contentItem] = counter + 1;
+                return false;
+            }
 
+            _recursions[contentItem] = 1;
             return false;
         }
     }

src/OrchardCore.Modules/OrchardCore.Contents/Startup.cs

@@ -140,8 +140,7 @@ public override void ConfigureServices(IServiceCollection services)
             services.AddLiquidFilter<DisplayUrlFilter>("display_url");
             services.AddLiquidFilter<FullTextFilter>("full_text");
 
-            services.AddScoped<IContentItemRecursionHelper<FullTextFilter>, ContentItemRecursionHelper<FullTextFilter>>();
-            services.AddScoped<IContentItemRecursionHelper<BuildDisplayFilter>, ContentItemRecursionHelper<BuildDisplayFilter>>();
+            services.AddScoped(typeof(IContentItemRecursionHelper<>), typeof(ContentItemRecursionHelper<>));
         }
 
         public override void Configure(IApplicationBuilder builder, IEndpointRouteBuilder routes, IServiceProvider serviceProvider)