Null-check PagedBufferedStringWriter

samples/MvcSandbox/Startup.cs

@@ -1,6 +1,7 @@
 // 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.IO;
 using Microsoft.AspNetCore.Builder;
 using Microsoft.AspNetCore.Hosting;
 using Microsoft.Extensions.DependencyInjection;
@@ -34,6 +35,7 @@ namespace MvcSandbox
         {
             var host = new WebHostBuilder()
                 .UseDefaultHostingConfiguration(args)
+                .UseContentRoot(Directory.GetCurrentDirectory())
                 .UseIISPlatformHandlerUrl()
                 .UseKestrel()
                 .UseStartup<Startup>()

samples/MvcSandbox/project.json

@@ -18,6 +18,9 @@
     "Microsoft.Extensions.Logging.Console": "1.0.0-*",
     "Microsoft.NETCore.Platforms": "1.0.1-*"
   },
+  "content": [
+    "Views"
+  ],
   "tools": {
     "dotnet-razor-tooling": "1.0.0-*"
   },

src/Microsoft.AspNetCore.Mvc.ViewFeatures/Internal/PagedBufferedTextWriter.cs

@@ -83,11 +83,21 @@ namespace Microsoft.AspNetCore.Mvc.ViewFeatures.Internal
 
         public override void Write(char[] buffer)
         {
+            if (buffer == null)
+            {
+                return;
+            }
+
             Write(buffer, 0, buffer.Length);
         }
 
         public override void Write(char[] buffer, int index, int count)
         {
+            if (buffer == null)
+            {
+                throw new ArgumentNullException(nameof(buffer));
+            }
+
             while (count > 0)
             {
                 var page = GetCurrentPage();
@@ -110,6 +120,11 @@ namespace Microsoft.AspNetCore.Mvc.ViewFeatures.Internal
 
         public override void Write(string value)
         {
+            if (value == null)
+            {
+                return;
+            }
+
             var index = 0;
             var count = value.Length;
 

test/Microsoft.AspNetCore.Mvc.ViewFeatures.Test/Internal/PagedBufferedTextWriterTest.cs

@@ -1,6 +1,7 @@
 // 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.Buffers;
 using System.Collections.Generic;
 using System.IO;
@@ -9,11 +10,11 @@ using Xunit;
 
 namespace Microsoft.AspNetCore.Mvc.ViewFeatures.Internal
 {
-    public class PagedBufferedStringWriterTest
+    public class PagedBufferedTextWriterTest
     {
         private static readonly char[] Content;
 
-        static PagedBufferedStringWriterTest()
+        static PagedBufferedTextWriterTest()
         {
             Content = new char[4 * PagedBufferedTextWriter.PageSize];
             for (var i = 0; i < Content.Length; i++)
@@ -43,6 +44,24 @@ namespace Microsoft.AspNetCore.Mvc.ViewFeatures.Internal
             Assert.Equal<char>(Content, inner.ToString().ToCharArray());
         }
 
+        [Fact]
+        public async Task Write_CharArray_Null()
+        {
+            // Arrange
+            var pool = new TestArrayPool();
+            var inner = new StringWriter();
+
+            var writer = new PagedBufferedTextWriter(pool, inner);
+
+            // Act
+            writer.Write((char[])null);
+
+            await writer.FlushAsync();
+
+            // Assert
+            Assert.Empty(inner.ToString());
+        }
+
         [Fact]
         public async Task Write_CharArray()
         {
@@ -82,6 +101,19 @@ namespace Microsoft.AspNetCore.Mvc.ViewFeatures.Internal
             Assert.Equal<char>(Content, inner.ToString().ToCharArray());
         }
 
+        [Fact]
+        public void Write_CharArray_Bounded_Null()
+        {
+            // Arrange
+            var pool = new TestArrayPool();
+            var inner = new StringWriter();
+
+            var writer = new PagedBufferedTextWriter(pool, inner);
+
+            // Act & Assert
+            Assert.Throws<ArgumentNullException>("buffer", () => writer.Write(null, 0, 0));
+        }
+
         [Fact]
         public async Task Write_CharArray_Bounded()
         {
@@ -109,6 +141,24 @@ namespace Microsoft.AspNetCore.Mvc.ViewFeatures.Internal
             Assert.Equal<char>(Content, inner.ToString().ToCharArray());
         }
 
+        [Fact]
+        public async Task Write_String_Null()
+        {
+            // Arrange
+            var pool = new TestArrayPool();
+            var inner = new StringWriter();
+
+            var writer = new PagedBufferedTextWriter(pool, inner);
+
+            // Act
+            writer.Write((string)null);
+
+            await writer.FlushAsync();
+
+            // Assert
+            Assert.Empty(inner.ToString());
+        }
+
         [Fact]
         public async Task Write_String()
         {
@@ -158,7 +208,7 @@ namespace Microsoft.AspNetCore.Mvc.ViewFeatures.Internal
             Assert.Equal(3, pool.Returned.Count);
         }
 
-        private class TestArrayPool: ArrayPool<char>
+        private class TestArrayPool : ArrayPool<char>
         {
             public IList<char[]> Returned { get; } = new List<char[]>();