From cbe9eacb0df1f1e702e6f27009f956cdcc72ad31 Mon Sep 17 00:00:00 2001
From: Toby Henderson <toby.henderson@huddle.com>
Date: Wed, 16 Dec 2015 16:31:28 +0000
Subject: [PATCH] Added a better message than - The operation is not ready for
 invocation. - like what and who

---
 .../OperationModel/MethodBased/MethodBasedOperation.cs   | 5 ++++-
 src/OpenRasta/OperationModel/OperationExtensions.cs      | 9 ++++++++-
 2 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/src/OpenRasta/OperationModel/MethodBased/MethodBasedOperation.cs b/src/OpenRasta/OperationModel/MethodBased/MethodBasedOperation.cs
index 20355015..8bb383b4 100644
--- a/src/OpenRasta/OperationModel/MethodBased/MethodBasedOperation.cs
+++ b/src/OpenRasta/OperationModel/MethodBased/MethodBasedOperation.cs
@@ -53,7 +53,10 @@ public IEnumerable<T> FindAttributes<T>() where T : class
         public IEnumerable<OutputMember> Invoke()
         {
             if (!Inputs.AllReady())
-                throw new InvalidOperationException("The operation is not ready for invocation.");
+            {
+                var notReady = Inputs.WhosNotReady();
+                throw new InvalidOperationException(string.Format("The operation {0} for {1} is not ready for invocation. These members are not ready; {2}", _method.Name, _method.Owner.Name, notReady.Select(x => x.Name).JoinString(", ")));
+            }
 
             var handler = CreateInstance(_ownerType, Resolver);
 
diff --git a/src/OpenRasta/OperationModel/OperationExtensions.cs b/src/OpenRasta/OperationModel/OperationExtensions.cs
index 22ff22f2..5ece7836 100644
--- a/src/OpenRasta/OperationModel/OperationExtensions.cs
+++ b/src/OpenRasta/OperationModel/OperationExtensions.cs
@@ -1,6 +1,8 @@
 using System.Collections.Generic;
 using System.Linq;
 
+using OpenRasta.TypeSystem;
+
 namespace OpenRasta.OperationModel
 {
     public static class OperationExtensions
@@ -10,7 +12,12 @@ public static bool AllReady(this IEnumerable<InputMember> members)
             return members.All(x => x.IsReadyForAssignment);
         }
 
-        /// <summary>
+        public static IEnumerable<IMember> WhosNotReady(this IEnumerable<InputMember> members)
+        {
+            return members.Where(x => x.IsReadyForAssignment == false).Select(x => x.Member);
+        }
+
+    /// <summary>
         /// Returns the number of members ready for invocation (aka either having a default value or having had a value assigned to them).
         /// </summary>
         /// <param name="members"></param>