Implemented RoutingKey attribute

Tapeti.Annotations/RoutingKeyAttribute.cs

@@ -0,0 +1,52 @@
+using System;
+
+namespace Tapeti.Annotations
+{
+    /// <inheritdoc />
+    /// <summary>
+    /// Can be attached to a message class to override or extend the generated routing key.
+    /// One of the intended scenarios is for versioning messages, where you want to add for example a
+    /// ".v2" postfix but keep the class name itself the same (in a different namespace of course).
+    /// </summary>
+    /// <remarks>
+    /// The implementation of IRoutingKeyStrategy must explicitly add support for this attribute for it to have effect.
+    /// The default implementation (TypeNameRoutingKeyStrategy) does, of course. Custom implementations can use
+    /// the Tapeti.Helpers.RoutingKeyHelper class to add support and keep up-to-date automatically.
+    /// 
+    /// When using EnableDeclareDurableQueues to automatically generate the queue bindings, both the sender and receiver must
+    /// use a Tapeti version >= 2.5 to support this attribute or the binding will differ from the sent routing key.
+    ///
+    /// The routing keys are no longer used by Tapeti once the message is in the queue, the message handler
+    /// is instead based on the full message class name (thus including namespace), so if the binding is generated in any
+    /// other way this remark does not apply and prior versions of Tapeti are compatible.
+    /// </remarks>
+    [AttributeUsage(AttributeTargets.Class)]
+    public class RoutingKeyAttribute : Attribute
+    {
+        /// <summary>
+        /// If specified, the routing key strategy is skipped altogether and this value is used instead.
+        /// </summary>
+        /// <remarks>
+        /// The Prefix and Postfix properties will not have any effect if the Full property is specified.
+        /// </remarks>
+        public string Full { get; set; }
+
+        /// <summary>
+        /// If specified, the value generated by the default routing key strategy is prefixed with this value.
+        /// No dot will be added after this prefix, if you want to include it add it as part of the value.
+        /// </summary>
+        /// <remarks>
+        /// This property will not have any effect if the Full property is specified. Can be used in combination with Postfix.
+        /// </remarks>
+        public string Prefix { get; set; }
+
+        /// <summary>
+        /// If specified, the value generated by the default routing key strategy is postfixed with this value.
+        /// No dot will be added before this postfix, if you want to include it add it as part of the value.
+        /// </summary>
+        /// <remarks>
+        /// This property will not have any effect if the Full property is specified. Can be used in combination with Prefix.
+        /// </remarks>
+        public string Postfix { get; set; }
+    }
+}

Tapeti.Tests/Default/TypeNameRoutingKeyStrategyTests.cs

@@ -1,4 +1,6 @@
 using System;
+using FluentAssertions;
+using Tapeti.Annotations;
 using Tapeti.Default;
 using Xunit;
 
@@ -60,13 +62,54 @@ namespace Tapeti.Tests.Default
             AssertRoutingKey("acr.test.mixed.case", typeof(ACRTestMIXEDCaseMESSAGE));
         }
 
+
+        [RoutingKey(Prefix = "prefix.")]
+        private class PrefixAttributeTestMessage { }
+
+        [Fact]
+        public void Prefix()
+        {
+            AssertRoutingKey("prefix.prefix.attribute.test", typeof(PrefixAttributeTestMessage));
+        }
+
+
+        [RoutingKey(Postfix = ".postfix")]
+        private class PostfixAttributeTestMessage { }
+
+        [Fact]
+        public void Postfix()
+        {
+            AssertRoutingKey("postfix.attribute.test.postfix", typeof(PostfixAttributeTestMessage));
+        }
+
+
+
+        [RoutingKey(Prefix = "prefix.", Postfix = ".postfix")]
+        private class PrefixPostfixAttributeTestMessage { }
+
+        [Fact]
+        public void PrefixPostfix()
+        {
+            AssertRoutingKey("prefix.prefix.postfix.attribute.test.postfix", typeof(PrefixPostfixAttributeTestMessage));
+        }
+
+
+        [RoutingKey(Full = "andnowforsomethingcompletelydifferent", Prefix = "ignore.", Postfix = ".me")]
+        private class FullAttributeTestMessage { }
+
+        [Fact]
+        public void Full()
+        {
+            AssertRoutingKey("andnowforsomethingcompletelydifferent", typeof(FullAttributeTestMessage));
+        }
+
+
+
         // ReSharper disable once ParameterOnlyUsedForPreconditionCheck.Local
         private static void AssertRoutingKey(string expected, Type messageType)
         {
-            if (expected == null) throw new ArgumentNullException(nameof(expected));
-            if (messageType == null) throw new ArgumentNullException(nameof(messageType));
-
-            Assert.Equal(expected, new TypeNameRoutingKeyStrategy().GetRoutingKey(messageType));
+            var routingKey = new TypeNameRoutingKeyStrategy().GetRoutingKey(messageType);
+            routingKey.Should().Be(expected);
         }
     }
     // ReSharper restore InconsistentNaming

Tapeti.Tests/Helpers/ConnectionStringParser.cs

@@ -1,4 +1,5 @@
-using Tapeti.Helpers;
+using FluentAssertions;
+using Tapeti.Helpers;
 using Xunit;
 
 namespace Tapeti.Tests.Helpers
@@ -185,12 +186,12 @@ namespace Tapeti.Tests.Helpers
         {
             var parsed = ConnectionStringParser.Parse(connectionstring);
 
-            Assert.Equal(expected.HostName, parsed.HostName);
-            Assert.Equal(expected.Port, parsed.Port);
-            Assert.Equal(expected.VirtualHost, parsed.VirtualHost);
-            Assert.Equal(expected.Username, parsed.Username);
-            Assert.Equal(expected.Password, parsed.Password);
-            Assert.Equal(expected.PrefetchCount, parsed.PrefetchCount);
+            parsed.HostName.Should().Be(expected.HostName);
+            parsed.Port.Should().Be(expected.Port);
+            parsed.VirtualHost.Should().Be(expected.VirtualHost);
+            parsed.Username.Should().Be(expected.Username);
+            parsed.Password.Should().Be(expected.Password);
+            parsed.PrefetchCount.Should().Be(expected.PrefetchCount);
         }
     }
 }

Tapeti.Tests/Tapeti.Tests.csproj

@@ -9,6 +9,7 @@
   </PropertyGroup>
 
   <ItemGroup>
+    <PackageReference Include="FluentAssertions" Version="5.10.3" />
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="16.10.0" />
     <PackageReference Include="xunit" Version="2.4.1" />
     <PackageReference Include="xunit.runner.visualstudio" Version="2.4.3">

Tapeti/Default/TypeNameRoutingKeyStrategy.cs

@@ -3,6 +3,7 @@ using System.Collections.Concurrent;
 using System.Collections.Generic;
 using System.Linq;
 using System.Text.RegularExpressions;
+using Tapeti.Helpers;
 
 namespace Tapeti.Default
 {
@@ -45,15 +46,18 @@ namespace Tapeti.Default
         /// <param name="messageType"></param>
         protected virtual string BuildRoutingKey(Type messageType)
         {
-            // Split PascalCase into dot-separated parts. If the class name ends in "Message" leave that out.
-            var words = SplitPascalCase(messageType.Name);
-            if (words == null)
-                return "";
+            return RoutingKeyHelper.Decorate(messageType, () =>
+            {
+                // Split PascalCase into dot-separated parts. If the class name ends in "Message" leave that out.
+                var words = SplitPascalCase(messageType.Name);
+                if (words == null)
+                    return "";
 
-            if (words.Count > 1 && words.Last().Equals("Message", StringComparison.InvariantCultureIgnoreCase))
-                words.RemoveAt(words.Count - 1);
+                if (words.Count > 1 && words.Last().Equals("Message", StringComparison.InvariantCultureIgnoreCase))
+                    words.RemoveAt(words.Count - 1);
 
-            return string.Join(".", words.Select(s => s.ToLower()));
+                return string.Join(".", words.Select(s => s.ToLower()));
+            });
         }
 
 

Tapeti/Helpers/RoutingKeyHelper.cs

@@ -0,0 +1,31 @@
+using System;
+using System.Reflection;
+using Tapeti.Annotations;
+
+namespace Tapeti.Helpers
+{
+    /// <summary>
+    /// Helper class for compositing a routing key with support for the RoutingKey attribute.
+    /// Should be used by all implementations of IRoutingKeyStrategy unless there is a good reason not to.
+    /// </summary>
+    public static class RoutingKeyHelper
+    {
+        /// <summary>
+        /// Applies the RoutingKey attribute for the specified messageClass.
+        /// </summary>
+        /// <param name="messageType"></param>
+        /// <param name="applyStrategy">Called when the strategy needs to be applied to the message class to generate a routing key.
+        /// Will not be called if the Full property is specified on the RoutingKey attribute.</param>
+        public static string Decorate(Type messageType, Func<string> applyStrategy)
+        {
+            var routingKeyAttribute = messageType.GetCustomAttribute<RoutingKeyAttribute>();
+            if (routingKeyAttribute == null)
+                return applyStrategy();
+
+            if (!string.IsNullOrEmpty(routingKeyAttribute.Full))
+                return routingKeyAttribute.Full;
+
+            return (routingKeyAttribute.Prefix ?? "") + applyStrategy() + (routingKeyAttribute.Postfix ?? "");
+        }
+    }
+}