Exit early when appending empty event list (#42)

Author: Tomas Lycken

src/RdbmsEventStore.EntityFramework.Tests/EventStoreTests/WriteEventTests.cs

@@ -4,6 +4,7 @@
 using System.Threading.Tasks;
 using RdbmsEventStore.EntityFramework.Tests.Infrastructure;
 using RdbmsEventStore.EntityFramework.Tests.TestData;
+using Moq;
 using Xunit;
 
 
@@ -34,6 +35,25 @@ public async Task CommittingWithOutOfSyncDataThrowsConflictException()
             await Assert.ThrowsAsync<ConflictException>(() => store.Append(stream, 0, new[] { new FooEvent { Foo = "Qux" } }));
         }
 
+        [Fact]
+        public async Task CommittingNoEventsExitsEarly() {
+            var context = new Mock<EventStoreContext<GuidGuidPersistedEvent>>(MockBehavior.Strict);
+            var set = new Mock<DbSet<GuidGuidPersistedEvent>>(MockBehavior.Strict);
+            context.Setup(c => c.Set<GuidGuidPersistedEvent>()).Returns(set.Object);
+            var stream = Guid.NewGuid();
+
+            var store = _fixture.BuildEventStore(context.Object);
+
+            try {
+                await store.Append(stream, 0, new object[] { });
+            } catch (NotImplementedException) {
+                // Thrown by the mock DbSet if we try to query for existing events
+                // This indicates that we didn't exit early
+
+                Assert.False(true, "Expected to exit early, but apparently didn't.");
+            }
+        }
+
         [Fact]
         public async Task CommittingMultipleEventsStoresAllEventsInContext()
         {
@@ -77,4 +97,4 @@ public async Task CommittingMultipleEventsIncrementsVersionForEachEvent()
                 bar => Assert.Equal(2, bar.Version));
         }
     }
-}
+}

src/RdbmsEventStore.EntityFramework.Tests/RdbmsEventStore.EntityFramework.Tests.csproj

@@ -11,6 +11,7 @@
     <PackageReference Include="Effort.EF6" Version="1.3.0" />
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="15.3.0" />
     <PackageReference Include="tlycken.Extensions" Version="0.5.0" />
+    <PackageReference Include="Moq" Version="4.7.145" />
     <PackageReference Include="xunit" Version="2.3.0" />
     <PackageReference Include="xunit.runner.visualstudio" Version="2.3.0" />
   </ItemGroup>

src/RdbmsEventStore.EntityFramework/EntityFrameworkEventStore.cs

@@ -45,6 +45,10 @@ public async Task<IEnumerable<TEvent>> Events(Func<IQueryable<TEventMetadata>, I
 
         public async Task Append(TStreamId streamId, long versionBefore, IEnumerable<object> payloads)
         {
+            if (!payloads.Any()) {
+                return;
+            }
+
             using (await _writeLock.Aquire(streamId))
             {
                 var highestVersionNumber = await _context.Events