Fixing NilBehavior

--HG--
branch : 1.x

src/Orchard.Tests/DisplayManagement/CompositeTests.cs

@@ -52,6 +52,7 @@ namespace Orchard.Tests.DisplayManagement {
             Assert.That(foo.Bar, Is.EqualTo("bar"));
             Assert.That(foo.Bar == null, Is.False);
         }
+
     }
 
     public class Animal : Composite {

src/Orchard.Tests/DisplayManagement/NilTests.cs

@@ -0,0 +1,41 @@
+using NUnit.Framework;
+using Orchard.DisplayManagement.Shapes;
+
+namespace Orchard.Tests.DisplayManagement {
+    [TestFixture]
+    public class NilTests {
+
+        [Test]
+        public void NilShouldEqualToNull() {
+            var nil = Nil.Instance;
+
+            Assert.That(nil == null, Is.True);
+            Assert.That(nil != null, Is.False);
+
+            Assert.That(nil == Nil.Instance, Is.True);
+            Assert.That(nil != Nil.Instance, Is.False);
+        }
+
+        [Test]
+        public void NilShouldBeRecursive() {
+            dynamic nil = Nil.Instance;
+
+            Assert.That(nil == null, Is.True);
+            Assert.That(nil.Foo == null, Is.True);
+            Assert.That(nil.Foo.Bar == null, Is.True);
+        }
+
+
+        [Test]
+        public void CallingToStringOnNilShouldReturnEmpty() {
+            var nil = Nil.Instance;
+            Assert.That(nil.ToString(), Is.EqualTo(""));
+        }
+
+        [Test]
+        public void CallingToStringOnDynamicNilShouldReturnEmpty() {
+            dynamic nil = Nil.Instance;
+            Assert.That(nil.Foo.Bar.ToString(), Is.EqualTo(""));
+        }
+    }
+}

src/Orchard.Tests/DisplayManagement/ZoneHoldingTests.cs

@@ -71,10 +71,14 @@ namespace Orchard.Tests.DisplayManagement {
         }
 
         [Test]
-        public void NoneEmptyZonesShouldBeNull() {
+        public void NoneEmptyZonesShouldNotBeNull() {
             Func<dynamic> factory = () => new Shape();
 
             dynamic foo = new ZoneHolding(factory);
+
+            Assert.That(foo.Header == null, Is.True);
+            Assert.That(foo.Header != null, Is.False);
+
             foo.Header.Add("blah");
 
             Assert.That(foo.Header == null, Is.False);

src/Orchard.Tests/Orchard.Framework.Tests.csproj

@@ -217,6 +217,7 @@
     <Compile Include="Data\StubLocator.cs" />
     <Compile Include="DisplayManagement\ArgsUtility.cs" />
     <Compile Include="DisplayManagement\CompositeTests.cs" />
+    <Compile Include="DisplayManagement\NilTests.cs" />
     <Compile Include="DisplayManagement\ZoneHoldingTests.cs" />
     <Compile Include="DisplayManagement\DefaultDisplayManagerTests.cs" />
     <Compile Include="ContainerTestBase.cs" />

src/Orchard/DisplayManagement/Shapes/Composite.cs

@@ -12,7 +12,7 @@ namespace Orchard.DisplayManagement.Shapes {
             return TryGetMemberImpl(binder.Name, out result);
         }
 
-        protected bool TryGetMemberImpl(string name, out object result) {
+        protected virtual bool TryGetMemberImpl(string name, out object result) {
             if (_props.Contains(name)) {
                 result = _props[name];
                 return true;
@@ -94,14 +94,22 @@ namespace Orchard.DisplayManagement.Shapes {
             return true;
         }
 
+        public static bool operator ==(Composite a, Nil b) {
+            return ReferenceEquals(a, b) || null == a;
+        }
+
+        public static bool operator !=(Composite a, Nil b) {
+            return !(a == b);
+        }
+
         public IDictionary Properties {
             get { return _props; }
         }
     }
 
     public class Nil : DynamicObject {
-        static readonly object Singleton = new Nil();
-        public static object Instance { get { return Singleton; } }
+        static readonly Nil Singleton = new Nil();
+        public static Nil Instance { get { return Singleton; } }
 
         private Nil() {
         }
@@ -116,22 +124,60 @@ namespace Orchard.DisplayManagement.Shapes {
             return true;
         }
 
+        public override bool TryInvokeMember(InvokeMemberBinder binder, object[] args, out object result) {
+            result = Nil.Instance;
+            return true;
+        }
+
+
         public override bool TryBinaryOperation(BinaryOperationBinder binder, object arg, out object result) {
             switch (binder.Operation) {
                 case ExpressionType.Equal:
-                    result = ReferenceEquals(arg, Nil.Instance) || arg == null;
+                    result = ReferenceEquals(arg, Nil.Instance) || (object)arg == null;
                     return true;
                 case ExpressionType.NotEqual:
-                    result = !ReferenceEquals(arg, Nil.Instance) && arg != null;
+                    result = !ReferenceEquals(arg, Nil.Instance) && (object)arg != null;
                     return true;
             }
 
             return base.TryBinaryOperation(binder, arg, out result);
         }
 
+        public static bool operator ==(Nil a, Nil b) {
+            return true;
+        }
+
+        public static bool operator !=(Nil a, Nil b) {
+            return false;
+        }
+
+        public static bool operator ==(Nil a, object b) {
+            return ReferenceEquals(a, b) || (object)b == null;
+        }
+
+        public static bool operator !=(Nil a, object b) {
+            return !(a == b);
+        }
+
+        public override bool Equals(object obj) {
+            if (obj == null) {
+                return true;
+            }
+
+            return ReferenceEquals(obj, Nil.Instance);
+        }
+
+        public override int GetHashCode() {
+            return 0;
+        }
+
         public override bool TryConvert(ConvertBinder binder, out object result) {
             result = null;
             return true;
         }
+
+        public override string ToString() {
+            return string.Empty;
+        }
     }
 }

src/Orchard/UI/Zones/ZoneHoldingBehavior.cs

@@ -38,7 +38,7 @@ namespace Orchard.UI.Zones {
         public override bool TryGetMember(System.Dynamic.GetMemberBinder binder, out object result) {
             var name = binder.Name;
 
-            if (!base.TryGetMember(binder, out result) || ((dynamic)result) == null) {
+            if (!base.TryGetMember(binder, out result) || (null == result)) {
                 // substitute nil results with a robot that turns adds a zone on
                 // the parent when .Add is invoked
                 result = new ZoneOnDemand(_zoneFactory, this, name);
@@ -67,7 +67,7 @@ namespace Orchard.UI.Zones {
             return TryGetMemberImpl(binder.Name, out result);
         }
 
-        private bool TryGetMemberImpl(string name, out object result) {
+        protected override bool TryGetMemberImpl(string name, out object result) {
 
             var parentMember = ((dynamic)_parent)[name];
             if (parentMember == null) {
@@ -139,18 +139,18 @@ namespace Orchard.UI.Zones {
         }
 
         public override bool TryConvert(System.Dynamic.ConvertBinder binder, out object result) {
-            result = null;
+            result = Nil.Instance;
             return true;
         }
 
-        public static bool operator ==(ZoneOnDemand expr, object arg) {
+        public static bool operator ==(ZoneOnDemand a, object b) {
             // if ZoneOnDemand is compared to null it must return true
-            return arg == null || ReferenceEquals(arg, Nil.Instance);
+            return b == null || ReferenceEquals(b, Nil.Instance);
         }
 
-        public static bool operator !=(ZoneOnDemand expr, object arg) {
+        public static bool operator !=(ZoneOnDemand a, object b) {
             // if ZoneOnDemand is compared to null it must return true
-            return arg != null && !ReferenceEquals(arg, Nil.Instance);
+            return !(a == b);
         }
 
         public override bool Equals(object obj) {