etag on metadata

Author: thefringeninja

src/SqlStreamStore.HAL.Tests/StreamMetadataTests.cs

@@ -30,6 +30,7 @@ await _fixture.HttpClient.SendAsync(
                     new HttpRequestMessage(HttpMethod.Get, $"/streams/{StreamId}/metadata")))
             {
                 response.StatusCode.ShouldBe(HttpStatusCode.NotFound);
+                response.Headers.ETag.ShouldBe(new EntityTagHeaderValue(@"""-1"""));
 
                 var resource = await response.AsHal();
 
@@ -72,6 +73,7 @@ await _fixture.HttpClient.SendAsync(
                     new HttpRequestMessage(HttpMethod.Get, $"/streams/{StreamId}/metadata")))
             {
                 response.StatusCode.ShouldBe(HttpStatusCode.OK);
+                response.Headers.ETag.ShouldBe(new EntityTagHeaderValue(@"""0"""));
 
                 var resource = await response.AsHal();
 

src/SqlStreamStore.HAL/Resources/GetStreamMetadataOperation.cs

@@ -15,8 +15,6 @@ public GetStreamMetadataOperation(HttpRequest request)
         public string StreamId { get; }
 
         public Task<StreamMetadataResult> Invoke(IStreamStore streamStore, CancellationToken ct)
-        {
-            return streamStore.GetStreamMetadata(StreamId, ct);
-        }
+            => streamStore.GetStreamMetadata(StreamId, ct);
     }
 }

src/SqlStreamStore.HAL/Resources/StreamMetadataResource.cs

@@ -46,7 +46,10 @@ public async Task<Response> Get(
                     .AddEmbeddedResource(
                         Constants.Relations.Metadata,
                         Schemas.SetStreamMetadata),
-                result.MetadataStreamVersion >= 0 ? 200 : 404);
+                result.MetadataStreamVersion >= 0 ? 200 : 404)
+            {
+                Headers = { [Constants.Headers.ETag] = new[] { $@"""{result.MetadataStreamVersion}""" } }
+            };
 
             return response;
         }