Support conditional requests and send 304 when possible

src/Microsoft.AspNetCore.ResponseCaching/ResponseCachingContext.cs

@@ -443,41 +443,50 @@ namespace Microsoft.AspNetCore.ResponseCaching
 
                 if (EntryIsFresh(cachedResponseHeaders, age, verifyAgainstRequest: true))
                 {
-                    var response = _httpContext.Response;
+                    // Check conditional request rules
-                    // Copy the cached status code and response headers
+                    if (ConditionalRequestSatisfied(cachedResponseHeaders))
-                    response.StatusCode = cachedResponse.StatusCode;
-                    foreach (var header in cachedResponse.Headers)
                     {
-                        response.Headers.Add(header);
+                        _httpContext.Response.StatusCode = StatusCodes.Status304NotModified;
-                    }
-
-                    response.Headers[HeaderNames.Age] = age.TotalSeconds.ToString("F0", CultureInfo.InvariantCulture);
-
-                    if (_responseType == ResponseType.HeadersOnly)
-                    {
-                        responseServed = true;
-                    }
-                    else if (_responseType == ResponseType.FullReponse)
-                    {
-                        // Copy the cached response body
-                        var body = cachedResponse.Body;
-
-                        // Add a content-length if required
-                        if (response.ContentLength == null && string.IsNullOrEmpty(response.Headers[HeaderNames.TransferEncoding]))
-                        {
-                            response.ContentLength = body.Length;
-                        }
-
-                        if (body.Length > 0)
-                        {
-                            await response.Body.WriteAsync(body, 0, body.Length);
-                        }
-
                         responseServed = true;
                     }
                     else
                     {
-                        throw new InvalidOperationException($"{nameof(_responseType)} not specified or is unrecognized.");
+                        var response = _httpContext.Response;
+                        // Copy the cached status code and response headers
+                        response.StatusCode = cachedResponse.StatusCode;
+                        foreach (var header in cachedResponse.Headers)
+                        {
+                            response.Headers.Add(header);
+                        }
+
+                        response.Headers[HeaderNames.Age] = age.TotalSeconds.ToString("F0", CultureInfo.InvariantCulture);
+
+                        if (_responseType == ResponseType.HeadersOnly)
+                        {
+                            responseServed = true;
+                        }
+                        else if (_responseType == ResponseType.FullReponse)
+                        {
+                            // Copy the cached response body
+                            var body = cachedResponse.Body;
+
+                            // Add a content-length if required
+                            if (response.ContentLength == null && string.IsNullOrEmpty(response.Headers[HeaderNames.TransferEncoding]))
+                            {
+                                response.ContentLength = body.Length;
+                            }
+
+                            if (body.Length > 0)
+                            {
+                                await response.Body.WriteAsync(body, 0, body.Length);
+                            }
+
+                            responseServed = true;
+                        }
+                        else
+                        {
+                            throw new InvalidOperationException($"{nameof(_responseType)} not specified or is unrecognized.");
+                        }
                     }
                 }
                 else
@@ -489,13 +498,42 @@ namespace Microsoft.AspNetCore.ResponseCaching
             if (!responseServed && RequestCacheControl.OnlyIfCached)
             {
                 _httpContext.Response.StatusCode = StatusCodes.Status504GatewayTimeout;
-
                 responseServed = true;
             }
 
             return responseServed;
         }
 
+        internal bool ConditionalRequestSatisfied(ResponseHeaders cachedResponseHeaders)
+        {
+            var ifNoneMatchHeader = RequestHeaders.IfNoneMatch;
+
+            if (ifNoneMatchHeader != null)
+            {
+                if (ifNoneMatchHeader.Count == 1 && ifNoneMatchHeader[0].Equals(EntityTagHeaderValue.Any))
+                {
+                    return true;
+                }
+
+                if (cachedResponseHeaders.ETag != null)
+                {
+                    foreach (var tag in ifNoneMatchHeader)
+                    {
+                        if (cachedResponseHeaders.ETag.Compare(tag, useStrongComparison: true))
+                        {
+                            return true;
+                        }
+                    }
+                }
+            }
+            else if ((cachedResponseHeaders.LastModified ?? cachedResponseHeaders.Date) <= RequestHeaders.IfUnmodifiedSince)
+            {
+                return true;
+            }
+
+            return false;
+        }
+
         internal void FinalizeCachingHeaders()
         {
             if (CacheResponse)

test/Microsoft.AspNetCore.ResponseCaching.Tests/ResponseCachingContextTests.cs

@@ -2,6 +2,7 @@
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System;
+using System.Collections.Generic;
 using System.Text;
 using System.Threading;
 using System.Threading.Tasks;
@@ -692,6 +693,140 @@ namespace Microsoft.AspNetCore.ResponseCaching.Tests
             Assert.True(context.EntryIsFresh(httpContext.Response.GetTypedHeaders(), TimeSpan.FromSeconds(3), verifyAgainstRequest: false));
         }
 
+        [Fact]
+        public void ConditionalRequestSatisfied_NotConditionalRequest_Fails()
+        {
+            var context = CreateTestContext(new DefaultHttpContext());
+            var cachedHeaders = new ResponseHeaders(new HeaderDictionary());
+
+            Assert.False(context.ConditionalRequestSatisfied(cachedHeaders));
+        }
+
+        [Fact]
+        public void ConditionalRequestSatisfied_IfUnmodifiedSince_FallsbackToDateHeader()
+        {
+            var utcNow = DateTimeOffset.UtcNow;
+            var cachedHeaders = new ResponseHeaders(new HeaderDictionary());
+            var httpContext = new DefaultHttpContext();
+            var context = CreateTestContext(httpContext);
+
+            httpContext.Request.GetTypedHeaders().IfUnmodifiedSince = utcNow;
+
+            // Verify modifications in the past succeeds
+            cachedHeaders.Date = utcNow - TimeSpan.FromSeconds(10);
+            Assert.True(context.ConditionalRequestSatisfied(cachedHeaders));
+
+            // Verify modifications at present succeeds
+            cachedHeaders.Date = utcNow;
+            Assert.True(context.ConditionalRequestSatisfied(cachedHeaders));
+
+            // Verify modifications in the future fails
+            cachedHeaders.Date = utcNow + TimeSpan.FromSeconds(10);
+            Assert.False(context.ConditionalRequestSatisfied(cachedHeaders));
+        }
+
+        [Fact]
+        public void ConditionalRequestSatisfied_IfUnmodifiedSince_LastModifiedOverridesDateHeader()
+        {
+            var utcNow = DateTimeOffset.UtcNow;
+            var cachedHeaders = new ResponseHeaders(new HeaderDictionary());
+            var httpContext = new DefaultHttpContext();
+            var context = CreateTestContext(httpContext);
+
+            httpContext.Request.GetTypedHeaders().IfUnmodifiedSince = utcNow;
+
+            // Verify modifications in the past succeeds
+            cachedHeaders.Date = utcNow + TimeSpan.FromSeconds(10);
+            cachedHeaders.LastModified = utcNow - TimeSpan.FromSeconds(10);
+            Assert.True(context.ConditionalRequestSatisfied(cachedHeaders));
+
+            // Verify modifications at present
+            cachedHeaders.Date = utcNow + TimeSpan.FromSeconds(10);
+            cachedHeaders.LastModified = utcNow;
+            Assert.True(context.ConditionalRequestSatisfied(cachedHeaders));
+
+            // Verify modifications in the future fails
+            cachedHeaders.Date = utcNow - TimeSpan.FromSeconds(10);
+            cachedHeaders.LastModified = utcNow + TimeSpan.FromSeconds(10);
+            Assert.False(context.ConditionalRequestSatisfied(cachedHeaders));
+        }
+
+        [Fact]
+        public void ConditionalRequestSatisfied_IfNoneMatch_Overrides_IfUnmodifiedSince_ToPass()
+        {
+            var utcNow = DateTimeOffset.UtcNow;
+            var cachedHeaders = new ResponseHeaders(new HeaderDictionary());
+            var httpContext = new DefaultHttpContext();
+            var requestHeaders = httpContext.Request.GetTypedHeaders();
+            var context = CreateTestContext(httpContext);
+
+            // This would fail the IfUnmodifiedSince checks
+            requestHeaders.IfUnmodifiedSince = utcNow;
+            cachedHeaders.LastModified = utcNow + TimeSpan.FromSeconds(10);
+
+            requestHeaders.IfNoneMatch = new List<EntityTagHeaderValue>(new[] { EntityTagHeaderValue.Any });
+            Assert.True(context.ConditionalRequestSatisfied(cachedHeaders));
+        }
+
+        [Fact]
+        public void ConditionalRequestSatisfied_IfNoneMatch_Overrides_IfUnmodifiedSince_ToFail()
+        {
+            var utcNow = DateTimeOffset.UtcNow;
+            var cachedHeaders = new ResponseHeaders(new HeaderDictionary());
+            var httpContext = new DefaultHttpContext();
+            var requestHeaders = httpContext.Request.GetTypedHeaders();
+            var context = CreateTestContext(httpContext);
+
+            // This would pass the IfUnmodifiedSince checks
+            requestHeaders.IfUnmodifiedSince = utcNow;
+            cachedHeaders.LastModified = utcNow - TimeSpan.FromSeconds(10);
+
+            requestHeaders.IfNoneMatch = new List<EntityTagHeaderValue>(new[] { new EntityTagHeaderValue("\"E1\"") });
+            Assert.False(context.ConditionalRequestSatisfied(cachedHeaders));
+        }
+
+        [Fact]
+        public void ConditionalRequestSatisfied_IfNoneMatch_AnyWithoutETagInResponse_Passes()
+        {
+            var cachedHeaders = new ResponseHeaders(new HeaderDictionary());
+            var httpContext = new DefaultHttpContext();
+            var context = CreateTestContext(httpContext);
+
+            httpContext.Request.GetTypedHeaders().IfNoneMatch = new List<EntityTagHeaderValue>(new[] { new EntityTagHeaderValue("\"E1\"") });
+
+            Assert.False(context.ConditionalRequestSatisfied(cachedHeaders));
+        }
+
+        [Fact]
+        public void ConditionalRequestSatisfied_IfNoneMatch_ExplicitWithMatch_Passes()
+        {
+            var cachedHeaders = new ResponseHeaders(new HeaderDictionary())
+            {
+                ETag = new EntityTagHeaderValue("\"E1\"")
+            };
+            var httpContext = new DefaultHttpContext();
+            var context = CreateTestContext(httpContext);
+
+            httpContext.Request.GetTypedHeaders().IfNoneMatch = new List<EntityTagHeaderValue>(new[] { new EntityTagHeaderValue("\"E1\"") });
+
+            Assert.True(context.ConditionalRequestSatisfied(cachedHeaders));
+        }
+
+        [Fact]
+        public void ConditionalRequestSatisfied_IfNoneMatch_ExplicitWithoutMatch_Fails()
+        {
+            var cachedHeaders = new ResponseHeaders(new HeaderDictionary())
+            {
+                ETag = new EntityTagHeaderValue("\"E2\"")
+            };
+            var httpContext = new DefaultHttpContext();
+            var context = CreateTestContext(httpContext);
+
+            httpContext.Request.GetTypedHeaders().IfNoneMatch = new List<EntityTagHeaderValue>(new[] { new EntityTagHeaderValue("\"E1\"") });
+
+            Assert.False(context.ConditionalRequestSatisfied(cachedHeaders));
+        }
+
         private static ResponseCachingContext CreateTestContext(HttpContext httpContext)
         {
             return CreateTestContext(

test/Microsoft.AspNetCore.ResponseCaching.Tests/ResponseCachingTests.cs

@@ -636,6 +636,122 @@ namespace Microsoft.AspNetCore.ResponseCaching.Tests
             Assert.NotEqual(await initialResponse.Content.ReadAsStringAsync(), await subsequentResponse.Content.ReadAsStringAsync());
         }
 
+        [Fact]
+        public async void Serves304_IfIfModifiedSince_Satisfied()
+        {
+            var builder = CreateBuilderWithResponseCaching(async (context) =>
+            {
+                var uniqueId = Guid.NewGuid().ToString();
+                var headers = context.Response.GetTypedHeaders();
+                headers.CacheControl = new CacheControlHeaderValue()
+                {
+                    Public = true,
+                    MaxAge = TimeSpan.FromSeconds(10)
+                };
+                headers.Date = DateTimeOffset.UtcNow;
+                headers.Headers["X-Value"] = uniqueId;
+                await context.Response.WriteAsync(uniqueId);
+            });
+
+            using (var server = new TestServer(builder))
+            {
+                var client = server.CreateClient();
+                var initialResponse = await client.GetAsync("");
+                client.DefaultRequestHeaders.IfUnmodifiedSince = DateTimeOffset.MaxValue;
+                var subsequentResponse = await client.GetAsync("");
+
+                initialResponse.EnsureSuccessStatusCode();
+                Assert.Equal(System.Net.HttpStatusCode.NotModified, subsequentResponse.StatusCode);
+            }
+        }
+
+        [Fact]
+        public async void ServesCachedContent_IfIfModifiedSince_NotSatisfied()
+        {
+            var builder = CreateBuilderWithResponseCaching(async (context) =>
+            {
+                var uniqueId = Guid.NewGuid().ToString();
+                var headers = context.Response.GetTypedHeaders();
+                headers.CacheControl = new CacheControlHeaderValue()
+                {
+                    Public = true,
+                    MaxAge = TimeSpan.FromSeconds(10)
+                };
+                headers.Date = DateTimeOffset.UtcNow;
+                headers.Headers["X-Value"] = uniqueId;
+                await context.Response.WriteAsync(uniqueId);
+            });
+
+            using (var server = new TestServer(builder))
+            {
+                var client = server.CreateClient();
+                var initialResponse = await client.GetAsync("");
+                client.DefaultRequestHeaders.IfUnmodifiedSince = DateTimeOffset.MinValue;
+                var subsequentResponse = await client.GetAsync("");
+
+                await AssertResponseCachedAsync(initialResponse, subsequentResponse);
+            }
+        }
+
+        [Fact]
+        public async void Serves304_IfIfNoneMatch_Satisfied()
+        {
+            var builder = CreateBuilderWithResponseCaching(async (context) =>
+            {
+                var uniqueId = Guid.NewGuid().ToString();
+                var headers = context.Response.GetTypedHeaders();
+                headers.CacheControl = new CacheControlHeaderValue()
+                {
+                    Public = true,
+                    MaxAge = TimeSpan.FromSeconds(10)
+                };
+                headers.Date = DateTimeOffset.UtcNow;
+                headers.Headers["X-Value"] = uniqueId;
+                headers.ETag = new EntityTagHeaderValue("\"E1\"");
+                await context.Response.WriteAsync(uniqueId);
+            });
+
+            using (var server = new TestServer(builder))
+            {
+                var client = server.CreateClient();
+                var initialResponse = await client.GetAsync("");
+                client.DefaultRequestHeaders.IfNoneMatch.Add(new System.Net.Http.Headers.EntityTagHeaderValue("\"E1\""));
+                var subsequentResponse = await client.GetAsync("");
+
+                initialResponse.EnsureSuccessStatusCode();
+                Assert.Equal(System.Net.HttpStatusCode.NotModified, subsequentResponse.StatusCode);
+            }
+        }
+
+        [Fact]
+        public async void ServesCachedContent_IfIfNoneMatch_NotSatisfied()
+        {
+            var builder = CreateBuilderWithResponseCaching(async (context) =>
+            {
+                var uniqueId = Guid.NewGuid().ToString();
+                var headers = context.Response.GetTypedHeaders();
+                headers.CacheControl = new CacheControlHeaderValue()
+                {
+                    Public = true,
+                    MaxAge = TimeSpan.FromSeconds(10)
+                };
+                headers.Date = DateTimeOffset.UtcNow;
+                headers.Headers["X-Value"] = uniqueId;
+                headers.ETag = new EntityTagHeaderValue("\"E1\"");
+                await context.Response.WriteAsync(uniqueId);
+            });
+
+            using (var server = new TestServer(builder))
+            {
+                var client = server.CreateClient();
+                var initialResponse = await client.GetAsync("");
+                client.DefaultRequestHeaders.IfNoneMatch.Add(new System.Net.Http.Headers.EntityTagHeaderValue("\"E2\""));
+                var subsequentResponse = await client.GetAsync("");
+
+                await AssertResponseCachedAsync(initialResponse, subsequentResponse);
+            }
+        }
+
         private static IWebHostBuilder CreateBuilderWithResponseCaching(RequestDelegate requestDelegate) =>
             CreateBuilderWithResponseCaching(app => { }, requestDelegate);