From 9dc9381ae4cddf2661818014b6e95fae99019f4b Mon Sep 17 00:00:00 2001
From: Pranav K <prkrishn@hotmail.com>
Date: Mon, 20 Nov 2017 09:08:55 -0800
Subject: [PATCH] Re-order execution in CacheTagHelper to avoid setting the
 result too early

Re-enable skipped tests
Fixes #7042
---
 .../CacheTagHelper.cs                         | 25 +++++++++++--------
 .../HtmlGenerationTest.cs                     |  4 +--
 .../CacheTagHelperTest.cs                     |  2 +-
 3 files changed, 17 insertions(+), 14 deletions(-)

diff --git a/src/Microsoft.AspNetCore.Mvc.TagHelpers/CacheTagHelper.cs b/src/Microsoft.AspNetCore.Mvc.TagHelpers/CacheTagHelper.cs
index e42bb67883..4a7bb989b7 100644
--- a/src/Microsoft.AspNetCore.Mvc.TagHelpers/CacheTagHelper.cs
+++ b/src/Microsoft.AspNetCore.Mvc.TagHelpers/CacheTagHelper.cs
@@ -108,8 +108,9 @@ namespace Microsoft.AspNetCore.Mvc.TagHelpers
             // The returned value is ignored, we only do this so that
             // the compiler doesn't complain about the returned task
             // not being awaited
-            var localTcs = MemoryCache.Set(cacheKey, tcs.Task, options);
+            _ = MemoryCache.Set(cacheKey, tcs.Task, options);
 
+            IHtmlContent content;
             try
             {
                 // The entry is set instead of assigning a value to the
@@ -118,24 +119,26 @@ namespace Microsoft.AspNetCore.Mvc.TagHelpers
 
                 // Use the CreateEntry to ensure a cache scope is created that will copy expiration tokens from
                 // cache entries created from the GetChildContentAsync call to the current entry.
-                IHtmlContent content;
                 var entry = MemoryCache.CreateEntry(cacheKey);
 
-                    // The result is processed inside an entry
-                    // such that the tokens are inherited.
+                // The result is processed inside an entry
+                // such that the tokens are inherited.
 
-                    var result = ProcessContentAsync(output);
-                    content = await result;
-                    options.SetSize(GetSize(content));
-                    entry.SetOptions(options);
+                var result = ProcessContentAsync(output);
+                content = await result;
+                options.SetSize(GetSize(content));
+                entry.SetOptions(options);
 
-                    entry.Value = result;
+                entry.Value = result;
 
-                tcs.SetResult(content);
                 // An entry gets committed to the cache when disposed gets called. We only want to do this when
                 // the content has been correctly generated (didn't throw an exception). For that reason the entry
                 // can't be put inside a using block.
                 entry.Dispose();
+
+                // Set the result on the TCS once we've commited the entry to the cache since commiting to the cache
+                // may throw.
+                tcs.SetResult(content);
                 return content;
             }
             catch (Exception ex)
@@ -144,7 +147,7 @@ namespace Microsoft.AspNetCore.Mvc.TagHelpers
                 tokenSource.Cancel();
 
                 // Fail the TCS so other awaiters see the exception.
-                tcs.SetException(ex);
+                tcs.TrySetException(ex);
                 throw;
             }
             finally
diff --git a/test/Microsoft.AspNetCore.Mvc.FunctionalTests/HtmlGenerationTest.cs b/test/Microsoft.AspNetCore.Mvc.FunctionalTests/HtmlGenerationTest.cs
index 2d6e5d0faf..1579544e7c 100644
--- a/test/Microsoft.AspNetCore.Mvc.FunctionalTests/HtmlGenerationTest.cs
+++ b/test/Microsoft.AspNetCore.Mvc.FunctionalTests/HtmlGenerationTest.cs
@@ -255,7 +255,7 @@ namespace Microsoft.AspNetCore.Mvc.FunctionalTests
 #endif
         }
 
-        [Fact(Skip = "https://github.com/aspnet/Mvc/issues/7042")]
+        [Fact]
         public async Task CacheTagHelper_CanCachePortionsOfViewsPartialViewsAndViewComponents()
         {
             // Arrange
@@ -440,7 +440,7 @@ namespace Microsoft.AspNetCore.Mvc.FunctionalTests
             Assert.Equal(expected2, response4.Trim());
         }
 
-        [Fact(Skip = "https://github.com/aspnet/Mvc/issues/7042")]
+        [Fact]
         public async Task CacheTagHelper_BubblesExpirationOfNestedTagHelpers()
         {
             // Arrange & Act - 1
diff --git a/test/Microsoft.AspNetCore.Mvc.TagHelpers.Test/CacheTagHelperTest.cs b/test/Microsoft.AspNetCore.Mvc.TagHelpers.Test/CacheTagHelperTest.cs
index abcb437274..589ce007f8 100644
--- a/test/Microsoft.AspNetCore.Mvc.TagHelpers.Test/CacheTagHelperTest.cs
+++ b/test/Microsoft.AspNetCore.Mvc.TagHelpers.Test/CacheTagHelperTest.cs
@@ -801,7 +801,7 @@ namespace Microsoft.AspNetCore.Mvc.TagHelpers
             Assert.Equal(childContent, tagHelperOutput4.Content.GetContent());
         }
 
-        [Fact(Skip = "https://github.com/aspnet/Mvc/issues/7042")]
+        [Fact]
         public async Task ProcessAsync_WorksForNestedCacheTagHelpers()
         {
             // Arrange