Weak Etag.

src/Squidex/AppServices.cs

@@ -19,6 +19,7 @@ using Squidex.Domain.Apps.Entities.Contents;
 using Squidex.Extensions.Actions.Twitter;
 using Squidex.Infrastructure.Commands;
 using Squidex.Infrastructure.Diagnostics;
+using Squidex.Pipeline;
 using Squidex.Pipeline.Robots;
 
 namespace Squidex
@@ -60,6 +61,8 @@ namespace Squidex
                 config.GetSection("robots"));
             services.Configure<GCHealthCheckOptions>(
                 config.GetSection("healthz:gc"));
+            services.Configure<ETagOptions>(
+                config.GetSection("etags"));
 
             services.Configure<MyContentsControllerOptions>(
                 config.GetSection("contentsController"));

src/Squidex/Pipeline/CommandMiddlewares/ETagCommandMiddleware.cs

@@ -33,16 +33,23 @@ namespace Squidex.Pipeline.CommandMiddlewares
                 return;
             }
 
+            context.Command.ExpectedVersion = EtagVersion.Any;
+
             var headers = httpContextAccessor.HttpContext.Request.Headers;
-            var headerMatch = headers[HeaderNames.IfMatch].ToString();
 
-            if (!string.IsNullOrWhiteSpace(headerMatch) && long.TryParse(headerMatch, NumberStyles.Any, CultureInfo.InvariantCulture, out var expectedVersion))
-            {
-                context.Command.ExpectedVersion = expectedVersion;
-            }
-            else
+            if (headers.TryGetValue(HeaderNames.ETag, out var etag) && !string.IsNullOrWhiteSpace(etag))
             {
-                context.Command.ExpectedVersion = EtagVersion.Any;
+                var etagValue = etag.ToString();
+
+                if (etagValue.StartsWith("W/", StringComparison.OrdinalIgnoreCase))
+                {
+                    etagValue = etagValue.Substring(2);
+                }
+
+                if (long.TryParse(etagValue, NumberStyles.Any, CultureInfo.InvariantCulture, out var expectedVersion))
+                {
+                    context.Command.ExpectedVersion = expectedVersion;
+                }
             }
 
             await next();

src/Squidex/Pipeline/ETagFilter.cs

@@ -9,12 +9,20 @@ using System.Threading.Tasks;
 using Microsoft.AspNetCore.Http;
 using Microsoft.AspNetCore.Mvc;
 using Microsoft.AspNetCore.Mvc.Filters;
+using Microsoft.Extensions.Options;
 using Microsoft.Net.Http.Headers;
 
 namespace Squidex.Pipeline
 {
     public sealed class ETagFilter : IAsyncActionFilter
     {
+        private readonly ETagOptions options;
+
+        public ETagFilter(IOptions<ETagOptions> options)
+        {
+            this.options = options.Value;
+        }
+
         public async Task OnActionExecutionAsync(ActionExecutingContext context, ActionExecutionDelegate next)
         {
             var resultContext = await next();
@@ -22,14 +30,21 @@ namespace Squidex.Pipeline
             var httpContext = context.HttpContext;
 
             if (HttpMethods.IsGet(httpContext.Request.Method) &&
-                httpContext.Request.Headers.TryGetValue(HeaderNames.IfNoneMatch, out var noneMatch) &&
                 httpContext.Response.StatusCode == 200 &&
-                httpContext.Response.Headers.TryGetValue(HeaderNames.ETag, out var etag) &&
-                !string.IsNullOrWhiteSpace(noneMatch) &&
-                !string.IsNullOrWhiteSpace(etag) &&
-                string.Equals(etag, noneMatch, System.StringComparison.Ordinal))
+                httpContext.Response.Headers.TryGetValue(HeaderNames.ETag, out var etag) && !string.IsNullOrWhiteSpace(etag))
             {
-                resultContext.Result = new StatusCodeResult(304);
+                if (!options.Strong)
+                {
+                    httpContext.Response.Headers[HeaderNames.ETag] = "W/" + etag;
+                }
+
+                if (httpContext.Request.Headers.TryGetValue(HeaderNames.IfNoneMatch, out var noneMatch) && !string.IsNullOrWhiteSpace(noneMatch))
+                {
+                    if (string.Equals(etag, noneMatch, System.StringComparison.Ordinal))
+                    {
+                        resultContext.Result = new StatusCodeResult(304);
+                    }
+                }
             }
         }
     }

src/Squidex/Pipeline/ETagOptions.cs

@@ -0,0 +1,14 @@
+// ==========================================================================
+//  Squidex Headless CMS
+// ==========================================================================
+//  Copyright (c) Squidex UG (haftungsbeschraenkt)
+//  All rights reserved. Licensed under the MIT license.
+// ==========================================================================
+
+namespace Squidex.Pipeline
+{
+    public sealed class ETagOptions
+    {
+        public bool Strong { get; set; }
+    }
+}

src/Squidex/appsettings.json

@@ -18,6 +18,13 @@
     "enforceHttps": false
   },
 
+  "etags": {
+    /*
+     * Set to true, to use strong etags.
+     */
+    "strong": false
+  },
+
   "ui": {
     /*
      * Regex suggestions for the UI

tests/Squidex.Tests/Pipeline/CommandMiddlewares/ETagCommandMiddlewareTests.cs

@@ -48,7 +48,20 @@ namespace Squidex.Pipeline.CommandMiddlewares
         [Fact]
         public async Task Should_add_expected_version_to_command()
         {
-            requestHeaders["If-Match"] = "13";
+            requestHeaders[HeaderNames.ETag] = "13";
+
+            var command = new CreateContent();
+            var context = new CommandContext(command, commandBus);
+
+            await sut.HandleAsync(context);
+
+            Assert.Equal(13, context.Command.ExpectedVersion);
+        }
+
+        [Fact]
+        public async Task Should_add_weak_etag_as_expected_version_to_command()
+        {
+            requestHeaders[HeaderNames.ETag] = "W/13";
 
             var command = new CreateContent();
             var context = new CommandContext(command, commandBus);