Closes #60

Release-Notes.md

@@ -14,7 +14,7 @@ Currently in development.
 * Windows Phone 8.1 Silverlight support [#81](https://github.com/jason-roberts/FeatureToggle/issues/81)
 * Windows Universal Apps 8.1 support [#21](https://github.com/jason-roberts/FeatureToggle/issues/21)
 * New toggle decorator that defaults to true when a toggle (configuration) error occurs [#61](https://github.com/jason-roberts/FeatureToggle/issues/61)
-
+* New toggle decorator that defaults to false when a toggle (configuration) error occurs [#60](https://github.com/jason-roberts/FeatureToggle/issues/60)
 
 
 # Version 2.2.1

src/FeatureToggle.Core/DefaultToDisabledOnErrorDecorator.cs

@@ -0,0 +1,46 @@
+using System;
+
+namespace FeatureToggle.Core
+{
+    /// <summary>
+    /// This decorator should be used with care or not at all. It will essentially hide any configuration errors
+    /// or other problems with the wrapped toggle knowing if it should enable the feature or not.
+    /// This feature is provided as a response to a user request.
+    /// </summary>
+    public class DefaultToDisabledOnErrorDecorator : IFeatureToggle
+    {
+        private readonly Action<Exception> _logAction;
+        public IFeatureToggle Toggle { get; private set; }
+
+        /// <summary>
+        /// Decorator constructor that allows the wrapping of another toggle
+        /// </summary>
+        /// <param name="toggle">The toggle to wrap (decorate)</param>
+        /// <param name="logAction">Optional action that gets called if an exception is thrown by the wrapped toggle before returning enabled = false</param>
+        public DefaultToDisabledOnErrorDecorator(IFeatureToggle toggle, Action<Exception> logAction = null)
+        {            
+            Toggle = toggle;
+            _logAction = logAction;
+        }
+
+        public bool FeatureEnabled
+        {
+            get
+            {
+                try
+                {
+                    return Toggle.FeatureEnabled;
+                }
+                catch (Exception ex)
+                {
+                    if (_logAction != null)
+                    {
+                        _logAction(ex);
+                    }
+
+                    return false;
+                }
+            }
+        }
+    }
+}

src/FeatureToggle.Core/FeatureToggle.Core.csproj

@@ -48,6 +48,7 @@
   </ItemGroup>
   <ItemGroup>
     <Compile Include="AlwaysOffFeatureToggle.cs" />
+    <Compile Include="DefaultToDisabledOnErrorDecorator.cs" />
     <Compile Include="DefaultToEnabledOnErrorDecorator.cs" />
     <Compile Include="ToggleConfigurationSettings.cs" />
     <Compile Include="RandomFeatureToggle.cs" />

src/Tests/FeatureToggle.Tests/DefaultToDisabledOnErrorDecoratorShould.cs

@@ -0,0 +1,84 @@
+using System;
+using FeatureToggle.Core;
+using Xunit;
+
+namespace FeatureToggle.Tests
+{
+    public class DefaultToDisabledOnErrorDecoratorShould
+    {
+        [Fact]
+        public void ReturnFalseWhenError()
+        {
+            var sut = new DefaultToDisabledOnErrorDecorator(new FeatureToggleThatThrowsAnException());
+
+            Assert.False(sut.FeatureEnabled);
+        }
+
+
+        [Fact]
+        public void ReturnConfiguredValueWhenNoError()
+        {
+            var sut = new DefaultToDisabledOnErrorDecorator(new FeatureToggleThatDoesNotThrowAnException());
+
+            Assert.False(sut.FeatureEnabled);
+        }
+
+
+        [Fact]
+        public void AllowAccessToWrappedToggle()
+        {
+            var wrappedToggle = new FeatureToggleThatDoesNotThrowAnException();
+
+            var sut = new DefaultToDisabledOnErrorDecorator(wrappedToggle);
+
+            Assert.Same(wrappedToggle, sut.Toggle);
+        }
+
+
+        [Fact]
+        public void CallLoggingActionOnErrorIfSet()
+        {
+            var wrappedToggle = new FeatureToggleThatThrowsAnException();
+
+            string log = "";
+
+            var sut = new DefaultToDisabledOnErrorDecorator(wrappedToggle, ex => log += ex.Message);
+
+
+
+            try
+            {
+                var isEnabled = sut.FeatureEnabled;
+            }
+            catch
+            {
+                // ignore exception so we can assert that the specified action was called
+            }
+
+
+
+            Assert.Equal("Exception for testing purposes", log);
+        }
+
+
+        private class FeatureToggleThatThrowsAnException : IFeatureToggle {
+            public bool FeatureEnabled
+            {
+                get
+                {
+                    throw new Exception("Exception for testing purposes");
+                }
+            }
+        }
+
+
+        private class FeatureToggleThatDoesNotThrowAnException : IFeatureToggle
+        {
+            public bool FeatureEnabled
+            {
+                get { return false; }
+            }
+        }
+
+    }
+}

src/Tests/FeatureToggle.Tests/FeatureToggle.Tests.csproj

@@ -105,6 +105,7 @@
     </CodeAnalysisDependentAssemblyPaths>
   </ItemGroup>
   <ItemGroup>
+    <Compile Include="DefaultToDisabledOnErrorDecoratorShould.cs" />
     <Compile Include="DefaultToEnabledOnErrorDecoratorShould.cs" />
     <Compile Include="RandomFeatureToggleShould.cs" />
     <Compile Include="AlwaysOnFeatureToggleShould.cs" />