Make ListResourceTemplatesHandler not required

The server was throwing if this handler wasn't specified, and it should probably be optional anyway.

Author: Redth

src/ModelContextProtocol/Server/McpServer.cs

@@ -147,13 +147,15 @@ private void SetResourcesHandler(McpServerOptions options)
         }
 
         if (resourcesCapability.ListResourcesHandler is not { } listResourcesHandler ||
-            resourcesCapability.ReadResourceHandler is not { } readResourceHandler ||
-            resourcesCapability.ListResourceTemplatesHandler is not { } listResourceTemplatesHandler)
+            resourcesCapability.ReadResourceHandler is not { } readResourceHandler)
         {
             throw new McpServerException("Resources capability was enabled, but ListResources and/or ReadResource handlers were not specified.");
         }
 
-        SetRequestHandler<ListResourceTemplatesRequestParams, ListResourceTemplatesResult>("resources/templates/list", (request, ct) => listResourceTemplatesHandler(new(this, request), ct));
+        if (resourcesCapability.ListResourceTemplatesHandler is { } listResourceTemplatesHandler)
+        {
+            SetRequestHandler<ListResourceTemplatesRequestParams, ListResourceTemplatesResult>("resources/templates/list", (request, ct) => listResourceTemplatesHandler(new(this, request), ct));
+        }
         SetRequestHandler<ListResourcesRequestParams, ListResourcesResult>("resources/list", (request, ct) => listResourcesHandler(new(this, request), ct));
         SetRequestHandler<ReadResourceRequestParams, ReadResourceResult>("resources/read", (request, ct) => readResourceHandler(new(this, request), ct));
 

tests/ModelContextProtocol.Tests/Server/McpServerTests.cs

@@ -319,6 +319,13 @@ await Can_Handle_Requests(
                             ResourceTemplates = [new() { UriTemplate = "test", Name = "Test Resource" }]
                         });
                     },
+                    ListResourcesHandler = (request, ct) =>
+                    {
+                        return Task.FromResult(new ListResourcesResult
+                        {
+                            Resources = [new() { Uri = "test", Name = "Test Resource" }]
+                        });
+                    },
                     ReadResourceHandler = (request, ct) => throw new NotImplementedException(),
                 }
             },