Response Caching: Cache Head with Content-Length (dotnet#12652)

* Response Caching: Cache Head with Content-Length

Author: alefranz

src/Middleware/ResponseCaching/src/ResponseCachingMiddleware.cs

@@ -5,7 +5,6 @@
 using System.Collections.Generic;
 using System.Threading.Tasks;
 using Microsoft.AspNetCore.Http;
-using Microsoft.AspNetCore.Http.Features;
 using Microsoft.Extensions.Caching.Memory;
 using Microsoft.Extensions.Logging;
 using Microsoft.Extensions.ObjectPool;
@@ -345,7 +344,9 @@ internal void FinalizeCacheBody(ResponseCachingContext context)
             {
                 var contentLength = context.HttpContext.Response.ContentLength;
                 var bufferStream = context.ResponseCachingStream.GetBufferStream();
-                if (!contentLength.HasValue || contentLength == bufferStream.Length)
+                if (!contentLength.HasValue || contentLength == bufferStream.Length
+                    || (bufferStream.Length == 0
+                        && string.Equals(context.HttpContext.Request.Method, "HEAD", StringComparison.OrdinalIgnoreCase)))
                 {
                     var response = context.HttpContext.Response;
                     // Add a content-length if required

src/Middleware/ResponseCaching/test/ResponseCachingMiddlewareTests.cs

@@ -723,8 +723,10 @@ public async Task FinalizeCacheBody_Cache_IfContentLengthMatches()
                 LoggedMessage.ResponseCached);
         }
 
-        [Fact]
-        public async Task FinalizeCacheBody_DoNotCache_IfContentLengthMismatches()
+        [Theory]
+        [InlineData("GET")]
+        [InlineData("HEAD")]
+        public async Task FinalizeCacheBody_DoNotCache_IfContentLengthMismatches(string method)
         {
             var cache = new TestResponseCache();
             var sink = new TestSink();
@@ -734,6 +736,7 @@ public async Task FinalizeCacheBody_DoNotCache_IfContentLengthMismatches()
             context.ShouldCacheResponse = true;
             middleware.ShimResponseStream(context);
             context.HttpContext.Response.ContentLength = 9;
+            context.HttpContext.Request.Method = method;
 
             await context.HttpContext.Response.WriteAsync(new string('0', 10));
 
@@ -749,6 +752,39 @@ public async Task FinalizeCacheBody_DoNotCache_IfContentLengthMismatches()
                 LoggedMessage.ResponseContentLengthMismatchNotCached);
         }
 
+        [Theory]
+        [InlineData(false)]
+        [InlineData(true)]
+        public async Task FinalizeCacheBody_RequestHead_Cache_IfContentLengthPresent_AndBodyAbsentOrOfSameLength(bool includeBody)
+        {
+            var cache = new TestResponseCache();
+            var sink = new TestSink();
+            var middleware = TestUtils.CreateTestMiddleware(testSink: sink, cache: cache);
+            var context = TestUtils.CreateTestContext();
+
+            context.ShouldCacheResponse = true;
+            middleware.ShimResponseStream(context);
+            context.HttpContext.Response.ContentLength = 10;
+            context.HttpContext.Request.Method = "HEAD";
+
+            if (includeBody)
+            {
+                // A response to HEAD should not include a body, but it may be present
+                await context.HttpContext.Response.WriteAsync(new string('0', 10));
+            }
+
+            context.CachedResponse = new CachedResponse();
+            context.BaseKey = "BaseKey";
+            context.CachedResponseValidFor = TimeSpan.FromSeconds(10);
+
+            middleware.FinalizeCacheBody(context);
+
+            Assert.Equal(1, cache.SetCount);
+            TestUtils.AssertLoggedMessages(
+                sink.Writes,
+                LoggedMessage.ResponseCached);
+        }
+
         [Fact]
         public async Task FinalizeCacheBody_Cache_IfContentLengthAbsent()
         {

src/Middleware/ResponseCaching/test/ResponseCachingTests.cs

@@ -2,13 +2,9 @@
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System;
-using System.IO;
 using System.Net.Http;
-using System.Threading;
 using System.Threading.Tasks;
-using Microsoft.AspNetCore.Builder;
 using Microsoft.AspNetCore.Http;
-using Microsoft.AspNetCore.Http.Features;
 using Microsoft.AspNetCore.TestHost;
 using Microsoft.Net.Http.Headers;
 using Xunit;
@@ -775,6 +771,24 @@ public async Task ServesCachedContent_IfCachedVaryByNotUpdated_OnCacheMiss()
             }
         }
 
+        [Fact]
+        public async Task ServesCachedContent_IfAvailable_UsingHead_WithContentLength()
+        {
+            var builders = TestUtils.CreateBuildersWithResponseCaching();
+
+            foreach (var builder in builders)
+            {
+                using (var server = new TestServer(builder))
+                {
+                    var client = server.CreateClient();
+                    var initialResponse = await client.SendAsync(TestUtils.CreateRequest("HEAD", "?contentLength=10"));
+                    var subsequentResponse = await client.SendAsync(TestUtils.CreateRequest("HEAD", "?contentLength=10"));
+
+                    await AssertCachedResponseAsync(initialResponse, subsequentResponse);
+                }
+            }
+        }
+
         private static void Assert304Headers(HttpResponseMessage initialResponse, HttpResponseMessage subsequentResponse)
         {
             // https://tools.ietf.org/html/rfc7232#section-4.1

src/Middleware/ResponseCaching/test/TestUtils.cs

@@ -4,11 +4,9 @@
 using System;
 using System.Collections.Generic;
 using System.IO;
-using System.IO.Pipelines;
 using System.Linq;
 using System.Net.Http;
 using System.Text;
-using System.Threading;
 using System.Threading.Tasks;
 using Microsoft.AspNetCore.Builder;
 using Microsoft.AspNetCore.Hosting;
@@ -23,7 +21,6 @@
 using Microsoft.Extensions.Primitives;
 using Microsoft.Net.Http.Headers;
 using Xunit;
-using ISystemClock = Microsoft.AspNetCore.ResponseCaching.ISystemClock;
 
 namespace Microsoft.AspNetCore.ResponseCaching.Tests
 {
@@ -61,6 +58,12 @@ private static bool TestRequestDelegate(HttpContext context, string guid)
             headers.Date = DateTimeOffset.UtcNow;
             headers.Headers["X-Value"] = guid;
 
+            var contentLength = context.Request.Query["ContentLength"];
+            if (!string.IsNullOrEmpty(contentLength))
+            {
+                headers.ContentLength = long.Parse(contentLength);
+            }
+
             if (context.Request.Method != "HEAD")
             {
                 return true;