Improve robustness of MailBnfHelper + add tests

Author: jamesqo

src/System.Net.Http/src/Internal/Mail/MailBnfHelper.cs

@@ -47,7 +47,7 @@ internal static class MailBnfHelper
         internal static readonly char EndSquareBracket = ']';
         internal static readonly char Comma = ',';
         internal static readonly char Dot = '.';
-        internal static readonly IList<char> Whitespace = CreateAllowedWhitespace();
+        internal static readonly List<char> Whitespace = CreateAllowedWhitespace();
 
         private static List<char> CreateAllowedWhitespace()
         {
@@ -293,6 +293,9 @@ internal static string ReadToken(string data, ref int offset, StringBuilder buil
 
         private static string[] s_months = new string[] { null, "Jan", "Feb", "Mar", "Apr", "May", "Jun", "Jul", "Aug", "Sep", "Oct", "Nov", "Dec" };
 
+        // Given a DateTime like Jul 8 2009, 6:05:04
+        // this method will return something like
+        // "8 Jul 2009 06:05:04 +0000" (where 00:00 is the UTC offset)
         internal static string GetDateTimeString(DateTime value, StringBuilder builder)
         {
             StringBuilder localBuilder = (builder != null ? builder : new StringBuilder());
@@ -331,7 +334,18 @@ internal static string GetDateTimeString(DateTime value, StringBuilder builder)
             }
 
             int colonIndex = offset.IndexOf(':');
+            if (colonIndex == -1)
+            {
+                throw new InvalidOperationException("TimeSpan.ToString() should contain at least one colon.");
+            }
+
             int nextColonIndex = offset.IndexOf(':', colonIndex + 1);
+            if (nextColonIndex == -1)
+            {
+                // Set it past the end of the string
+                nextColonIndex = offset.Length;
+            }
+
             localBuilder.Append(offset, 0, colonIndex);
             localBuilder.Append(offset, colonIndex + 1, nextColonIndex - (colonIndex + 1));
             return (builder != null ? null : localBuilder.ToString());

src/System.Net.Http/tests/UnitTests/Internal/MailBnfHelperTest.cs

@@ -0,0 +1,49 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Net.Mime;
+using System.Text;
+using System.Threading.Tasks;
+using Xunit;
+
+namespace System.Net.Http.Tests
+{
+    public class MailBnfHelperTest
+    {
+        public static IEnumerable<DateTime> GetDateTimeString_TestDates()
+        {
+            yield return new DateTime(2009, 1, 1, 8, 7, 39);
+            yield return new DateTime(2010, 2, 3, 5, 10, 32);
+            yield return new DateTime(2019, 12, 12, 20, 18, 0);
+            
+            for (int i = 1; i < 12; i++)
+                yield return new DateTime(2006, i, i, i, i, i);
+        }
+
+        // Given a DateTime like Jul 8 2009, 6:05:04
+        // GetDateTimeString should return something like
+        // "8 Jul 2009 06:05:04 +0000" (where 00:00 is the UTC offset)
+        public static IEnumerable<object[]> GetDateTimeString_TestData()
+        {
+            foreach (var dateTime in GetDateTimeString_TestDates())
+            {
+                var offset = TimeZoneInfo.Local.GetUtcOffset(dateTime);
+                char prefix = offset >= TimeSpan.Zero ? '+' : '-';
+                yield return new object[] { dateTime, $"{dateTime:d MMM yyyy HH:mm:ss} {prefix}{offset:hhmm}" };
+            }
+        }
+
+        [Theory]
+        [MemberData(nameof(GetDateTimeString_TestData))]
+        public void GetDateTimeString(DateTime input, string expected)
+        {
+            var builder = new StringBuilder();
+            MailBnfHelper.GetDateTimeString(input, builder);
+            Assert.Equal(expected, builder.ToString());
+        }
+    }
+}

src/System.Net.Http/tests/UnitTests/System.Net.Http.Unit.Tests.csproj

@@ -1,4 +1,4 @@
-<?xml version="1.0" encoding="utf-8"?>
+<?xml version="1.0" encoding="utf-8"?>
 <Project ToolsVersion="12.0" xmlns="http://schemas.microsoft.com/developer/msbuild/2003" DefaultTargets="Build">
   <PropertyGroup>
     <Configuration Condition="'$(Configuration)'==''">Windows_Debug</Configuration>
@@ -14,7 +14,6 @@
     <StringResourcesPath>../../src/Resources/Strings.resx</StringResourcesPath>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
   </PropertyGroup>
-  
   <!-- Help VS understand available configurations -->
   <PropertyGroup Condition="'$(Configuration)|$(Platform)' == 'FreeBSD_Debug|AnyCPU'" />
   <PropertyGroup Condition="'$(Configuration)|$(Platform)' == 'FreeBSD_Release|AnyCPU'" />
@@ -23,8 +22,7 @@
   <PropertyGroup Condition="'$(Configuration)|$(Platform)' == 'OSX_Debug|AnyCPU'" />
   <PropertyGroup Condition="'$(Configuration)|$(Platform)' == 'OSX_Release|AnyCPU'" />
   <PropertyGroup Condition="'$(Configuration)|$(Platform)' == 'Windows_Debug|AnyCPU'" />
-  <PropertyGroup Condition="'$(Configuration)|$(Platform)' == 'Windows_Release|AnyCPU'" />  
-  
+  <PropertyGroup Condition="'$(Configuration)|$(Platform)' == 'Windows_Release|AnyCPU'" />
   <ItemGroup>
     <Compile Include="$(CommonPath)\System\NotImplemented.cs">
       <Link>ProductionCode\Common\System\NotImplemented.cs</Link>
@@ -343,10 +341,11 @@
     <Compile Include="Headers\WarningHeaderValueTest.cs" />
     <Compile Include="HttpContentTest.cs" />
     <Compile Include="HttpRuleParserTest.cs" />
+    <Compile Include="Internal\MailBnfHelperTest.cs" />
     <Compile Include="MockContent.cs" />
   </ItemGroup>
   <ItemGroup>
     <None Include="project.json" />
   </ItemGroup>
   <Import Project="$([MSBuild]::GetDirectoryNameOfFileAbove($(MSBuildThisFileDirectory), dir.targets))\dir.targets" />
-</Project>
+</Project>