Refactoring CacheTagHelper

- Introducing a new distributed cache tag helper
- Sharing base implementation for both cache tag helper
- Preventing concurrent execution of cache tag helpers

Fixes #4147 , Fixes #3867

src/Microsoft.AspNetCore.Mvc.Razor/DependencyInjection/MvcRazorMvcCoreBuilderExtensions.cs

@@ -9,7 +9,9 @@
 using Microsoft.AspNetCore.Mvc.Razor.Internal;
 using Microsoft.AspNetCore.Mvc.Rendering;
 using Microsoft.AspNetCore.Razor.TagHelpers;
+using Microsoft.Extensions.Caching.Distributed;
 using Microsoft.Extensions.Caching.Memory;
+using Microsoft.Extensions.DependencyInjection;
 using Microsoft.Extensions.DependencyInjection.Extensions;
 using Microsoft.Extensions.Options;
 using Microsoft.Extensions.PlatformAbstractions;
@@ -133,6 +135,7 @@ internal static void AddRazorViewEngineServices(IServiceCollection services)
 
             // Consumed by the Cache tag helper to cache results across the lifetime of the application.
             services.TryAddSingleton<IMemoryCache, MemoryCache>();
+            services.TryAddSingleton<IDistributedCache, LocalCache>();
         }
     }
 }

src/Microsoft.AspNetCore.Mvc.TagHelpers/Cache/DistributedCacheTagHelperFormatter.cs

@@ -0,0 +1,47 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System;
+using System.Text;
+using System.Threading.Tasks;
+using Microsoft.AspNetCore.Mvc.Rendering;
+
+namespace Microsoft.AspNetCore.Mvc.TagHelpers.Cache
+{
+    /// <summary>
+    /// Implements <see cref="IDistributedCacheTagHelperFormatter"/> by serializing the content
+    /// in UTF8.
+    /// </summary>
+    public class DistributedCacheTagHelperFormatter : IDistributedCacheTagHelperFormatter
+    {
+
+        /// <inheritdoc />
+        public Task<byte[]> SerializeAsync(DistributedCacheTagHelperFormattingContext context)
+        {
+            if (context == null) 
+            {
+                throw new ArgumentNullException(nameof(context));    
+            }
+
+            if (context.HtmlString == null) 
+            {
+                throw new ArgumentNullException(nameof(context.HtmlString));    
+            }
+
+            var serialized = Encoding.UTF8.GetBytes(context.HtmlString.ToString());
+            return Task.FromResult(serialized);
+        }
+
+        /// <inheritdoc />
+        public Task<HtmlString> DeserializeAsync(byte[] value)
+        {
+            if (value == null) 
+            {
+                throw new ArgumentNullException(nameof(value));    
+            }
+
+            var content = Encoding.UTF8.GetString(value);
+            return Task.FromResult(new HtmlString(content));
+        }
+    }
+}

src/Microsoft.AspNetCore.Mvc.TagHelpers/Cache/DistributedCacheTagHelperFormattingContext.cs

@@ -0,0 +1,24 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using Microsoft.AspNetCore.Mvc.Rendering;
+using Microsoft.AspNetCore.Razor.TagHelpers;
+
+namespace Microsoft.AspNetCore.Mvc.TagHelpers.Cache
+{
+    /// <summary>
+    /// Represents an object containing the information to serialize with <see cref="IDistributedCacheTagHelperFormatter" />.
+    /// </summary>
+    public class DistributedCacheTagHelperFormattingContext
+    {
+        /// <summary>
+        /// Gets the <see cref="TagHelperContext"/> instance.
+        /// </summary>
+        public TagHelperContext Context {get; set; }
+
+        /// <summary>
+        /// Gets the <see cref="HtmlString"/> instance.
+        /// </summary>
+        public HtmlString HtmlString { get; set; }  
+    }
+}

src/Microsoft.AspNetCore.Mvc.TagHelpers/Cache/DistributedCacheTagHelperStorage.cs

@@ -0,0 +1,49 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System;
+using System.Threading.Tasks;
+using Microsoft.Extensions.Caching.Distributed;
+
+namespace Microsoft.AspNetCore.Mvc.TagHelpers.Cache
+{
+    /// <summary>
+    /// Implements <see cref="IDistributedCacheTagHelperStorage"/> by storing the content
+    /// in using <see cref="IDistributedCache"/> as the store.
+    /// </summary>
+    public class DistributedCacheTagHelperStorage : IDistributedCacheTagHelperStorage
+    {
+        private readonly IDistributedCache _distributedCache;
+
+        /// <summary>
+        /// Creates a new <see cref="DistributedCacheTagHelperStorage"/>.
+        /// </summary>
+        /// <param name="distributedCache">The <see cref="IDistributedCache"/> to use.</param>
+        public DistributedCacheTagHelperStorage(IDistributedCache distributedCache)
+        {
+            _distributedCache = distributedCache;
+        }
+
+        /// <inheritdoc />
+        public Task<byte[]> GetAsync(string key)
+        {
+            return _distributedCache.GetAsync(key);
+        }
+
+        /// <inheritdoc />
+        public Task SetAsync(string key, byte[] value, DistributedCacheEntryOptions options)
+        {
+            if (key == null)
+            {
+                throw new ArgumentNullException(nameof(key));
+            }
+
+            if (value == null)
+            {
+                throw new ArgumentNullException(nameof(value));
+            }
+
+            return _distributedCache.SetAsync(key, value, options);
+        }
+    }
+}

src/Microsoft.AspNetCore.Mvc.TagHelpers/Cache/IDistributedCacheTagHelperFormatter.cs

@@ -0,0 +1,29 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System.Threading.Tasks;
+using Microsoft.AspNetCore.Mvc.Rendering;
+
+namespace Microsoft.AspNetCore.Mvc.TagHelpers.Cache
+{
+    /// <summary>
+    /// An implementation of this interface provides a service to 
+    /// serialize html fragments for being store by <see cref="IDistributedCacheTagHelperStorage" />
+    /// </summary>
+    public interface IDistributedCacheTagHelperFormatter 
+    {
+        /// <summary>
+        /// Serializes some html content.
+        /// </summary>
+        /// <param name="context">The <see cref="DistributedCacheTagHelperFormattingContext" /> to serialize.</param>
+        /// <returns>The serialized result.</returns>
+        Task<byte[]> SerializeAsync(DistributedCacheTagHelperFormattingContext context);
+
+        /// <summary>
+        /// Deserialize some html content.
+        /// </summary>
+        /// <param name="value">The value to deserialize.</param>
+        /// <returns>The deserialized content, <value>null</value> otherwise.</returns>
+        Task<HtmlString> DeserializeAsync(byte[] value);
+    }
+}

src/Microsoft.AspNetCore.Mvc.TagHelpers/Cache/IDistributedCacheTagHelperStorage.cs

@@ -0,0 +1,31 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System.Threading.Tasks;
+using Microsoft.Extensions.Caching.Distributed;
+
+namespace Microsoft.AspNetCore.Mvc.TagHelpers.Cache
+{
+    /// <summary>
+    /// An implementation of this interface provides a service to 
+    /// cache distributed html fragments from the &lt;distributed-cache&gt;
+    /// tag helper.
+    /// </summary>
+    public interface IDistributedCacheTagHelperStorage
+    {
+        /// <summary>
+        /// Gets the content from the cache and deserializes it.
+        /// </summary>
+        /// <param name="key">The unique key to use in the cache.</param>
+        /// <returns>The stored value if it exists, <value>null</value> otherwise.</returns>
+        Task<byte[]> GetAsync(string key);
+
+        /// <summary>
+        /// Sets the content in the cache and serialized it.
+        /// </summary>
+        /// <param name="key">The unique key to use in the cache.</param>
+        /// <param name="value">The value to cache.</param>
+        /// <param name="options">The cache entry options.</param>
+        Task SetAsync(string key, byte[] value, DistributedCacheEntryOptions options);
+    }
+}