Provide more details when keys not found.

A request was made to provide the original key as well as the member
that was not found. In compound keys {{Customer.Address.ZipCode}}, any
of the names could be invalid, but knowing the fully-qualified name is
useful for error handling.

I also detected a bug where the code wasn't handling the case that a
sub-key didn't exist. This needs to be handled using the KeyNotFound
event.

mustache-sharp.test/FormatCompilerTester.cs

@@ -151,6 +151,31 @@ namespace mustache.test
             Assert.AreEqual(expected, actual, "The wrong message was generated.");
         }
 
+        /// <summary>
+        /// If part of a key is wrong, the full details should be provided.
+        /// </summary>
+        [TestMethod]
+        public void TestCompile_MultipartKey_PartMissing_ProvidesFullDetail()
+        {
+            FormatCompiler compiler = new FormatCompiler();
+            const string format = @"{{Customer.Name}}";
+            Generator generator = compiler.Compile(format);
+            generator.KeyNotFound += (obj, args) =>
+            {
+                args.Substitute = args.Key + "," + args.MissingMember;
+                args.Handled = true;
+            };
+            string actual = generator.Render(new
+            {
+                Customer = new
+                {
+                    FirstName = "Bob"
+                }
+            });
+            string expected = "Customer.Name,Name";
+            Assert.AreEqual(expected, actual, "The wrong message was generated.");
+        }
+
         /// <summary>
         /// If we specify an alignment with a key, the alignment should
         /// be used when rending the value.

mustache-sharp.test/Properties/AssemblyInfo.cs

@@ -31,5 +31,5 @@ using System.Runtime.InteropServices;
 //
 // You can specify all the values or you can default the Build and Revision Numbers 
 // by using the '*' as shown below:
-[assembly: AssemblyVersion("0.0.4.0")]
-[assembly: AssemblyFileVersion("0.0.4.0")]
+[assembly: AssemblyVersion("0.0.5.0")]
+[assembly: AssemblyFileVersion("0.0.5.0")]

mustache-sharp/KeyScope.cs

@@ -1,6 +1,7 @@
 using System;
 using System.Collections.Generic;
 using System.Globalization;
+using System.Linq;
 using mustache.Properties;
 
 namespace mustache
@@ -63,39 +64,47 @@ namespace mustache
             object nextLevel = _source;
             if (member != "this")
             {
-                nextLevel = find(member);
+                nextLevel = find(name, member);
             }
             for (int index = 1; index < names.Length; ++index)
             {
                 IDictionary<string, object> context = toLookup(nextLevel);
                 member = names[index];
-                nextLevel = context[member];
+                if (!context.TryGetValue(member, out nextLevel))
+                {
+                    nextLevel = handleKeyNotFound(name, member);
+                }
             }
             return nextLevel;
         }
 
-        private object find(string name)
+        private object find(string fullName, string memberName)
         {
             IDictionary<string, object> lookup = toLookup(_source);
-            if (lookup.ContainsKey(name))
+            if (lookup.ContainsKey(memberName))
             {
-                return lookup[name];
+                return lookup[memberName];
             }
             if (_parent == null)
             {
-                MissingKeyEventArgs args = new MissingKeyEventArgs(name);
-                if (KeyNotFound != null)
-                {
-                    KeyNotFound(this, args);
-                }
-                if (args.Handled)
-                {
-                    return args.Substitute;
-                }
-                string message = String.Format(CultureInfo.CurrentCulture, Resources.KeyNotFound, name);
-                throw new KeyNotFoundException(message);
+                return handleKeyNotFound(fullName, memberName);
             }
-            return _parent.find(name);
+            return _parent.find(fullName, memberName);
+        }
+
+        private object handleKeyNotFound(string fullName, string memberName)
+        {
+            MissingKeyEventArgs args = new MissingKeyEventArgs(fullName, memberName);
+            if (KeyNotFound != null)
+            {
+                KeyNotFound(this, args);
+            }
+            if (args.Handled)
+            {
+                return args.Substitute;
+            }
+            string message = String.Format(CultureInfo.CurrentCulture, Resources.KeyNotFound, memberName);
+            throw new KeyNotFoundException(message);
         }
 
         private static IDictionary<string, object> toLookup(object value)

mustache-sharp/MissingKeyEventArgs.cs

@@ -10,16 +10,23 @@ namespace mustache
         /// <summary>
         /// Initializes a new instance of a MissingKeyEventArgs.
         /// </summary>
-        /// <param name="missingKey">The key that had no match.</param>
-        internal MissingKeyEventArgs(string missingKey)
+        /// <param name="key">The fully-qualified key.</param>
+        /// <param name="missingMember">The part of the key that could not be found.</param>
+        internal MissingKeyEventArgs(string key, string missingMember)
         {
-            MissingKey = missingKey;
+            Key = key;
+            MissingMember = missingMember;
         }
 
         /// <summary>
-        /// Gets the key that could not be found.
+        /// Gets the fully-qualified key.
         /// </summary>
-        public string MissingKey { get; private set; }
+        public string Key { get; private set; }
+
+        /// <summary>
+        /// Gets the part of the key that could not be found.
+        /// </summary>
+        public string MissingMember { get; private set; }
 
         /// <summary>
         /// Gets or sets whether to use the substitute.

mustache-sharp/Properties/AssemblyInfo.cs

@@ -34,6 +34,6 @@ using System.Runtime.CompilerServices;
 // You can specify all the values or you can default the Build and Revision Numbers 
 // by using the '*' as shown below:
 // [assembly: AssemblyVersion("1.0.*")]
-[assembly: AssemblyVersion("0.0.4.0")]
+[assembly: AssemblyVersion("0.0.5.0")]
 [assembly: AssemblyFileVersion("0.0.4.0")]
 [assembly: InternalsVisibleTo("mustache-sharp.test")]