#18298: Preventing infinite loops in url alternates

Work Item: 18298

--HG--
branch : 1.x

src/Orchard.Web/Modules/Orchard.DesignerTools/Services/UrlAlternatesFactory.cs

@@ -10,17 +10,19 @@ namespace Orchard.DesignerTools.Services {
     [OrchardFeature("UrlAlternates")]
     public class UrlAlternatesFactory : ShapeDisplayEvents {
         private readonly IHttpContextAccessor _httpContextAccessor;
-        private readonly List<string> _urlAlternates;
+        private readonly Lazy<List<string>> _urlAlternates;
 
         public UrlAlternatesFactory(IHttpContextAccessor httpContextAccessor) {
             _httpContextAccessor = httpContextAccessor;
-            var httpContext = _httpContextAccessor.Current();
 
-            if(httpContext == null) {
+            _urlAlternates = new Lazy<List<string>>(() => {
-                return;
+                var httpContext = _httpContextAccessor.Current();
-            }
 
-            var request = _httpContextAccessor.Current().Request;
+                if (httpContext == null) {
+                    return null;
+                }
+
+                var request = _httpContextAccessor.Current().Request;
 
                 // extract each segment of the url
                 var urlSegments = VirtualPathUtility.ToAppRelative(request.Path.ToLower())
@@ -29,26 +31,34 @@ namespace Orchard.DesignerTools.Services {
                     .Select(url => url.Replace("-", "__").Replace(".", "_")) // format the alternate
                     .ToArray();
 
-                if ( String.IsNullOrWhiteSpace(urlSegments[0]) ) {
+                if (String.IsNullOrWhiteSpace(urlSegments[0])) {
                     urlSegments[0] = "homepage";
                 }
 
-                _urlAlternates = Enumerable.Range(1, urlSegments.Count()).Select(range => String.Join("__", urlSegments.Take(range))).ToList();
+                return Enumerable.Range(1, urlSegments.Count()).Select(range => String.Join("__", urlSegments.Take(range))).ToList();
+            });
         }
 
         public override void Displaying(ShapeDisplayingContext context) {
-            if (_urlAlternates == null || !_urlAlternates.Any()) {
+
-                return;
-            }
-     
             context.ShapeMetadata.OnDisplaying(displayedContext => {
+
+                if (_urlAlternates.Value == null || !_urlAlternates.Value.Any()) {
+                    return;
+                }
+
+                // prevent applying alternate again, c.f. http://orchard.codeplex.com/workitem/18298
+                if(displayedContext.ShapeMetadata.Alternates.Any(x => x.Contains("__url__"))) {
+                    return;
+                }
+
                 // appends Url alternates to current ones
                 displayedContext.ShapeMetadata.Alternates = displayedContext.ShapeMetadata.Alternates.SelectMany(
-                    alternate => new [] { alternate }.Union(_urlAlternates.Select(a => alternate + "__url__" + a))
+                    alternate => new [] { alternate }.Union(_urlAlternates.Value.Select(a => alternate + "__url__" + a))
                     ).ToList();
 
                 // appends [ShapeType]__url__[Url] alternates
-                displayedContext.ShapeMetadata.Alternates = _urlAlternates.Select(url => displayedContext.ShapeMetadata.Type + "__url__" + url)
+                displayedContext.ShapeMetadata.Alternates = _urlAlternates.Value.Select(url => displayedContext.ShapeMetadata.Type + "__url__" + url)
                     .Union(displayedContext.ShapeMetadata.Alternates)
                     .ToList();
             });