IO: Add GetActualCasing to File and Directory.

Uses kernel32 interoped method `GetLongPathName` to determine the
actual casing of file and directory paths on disk as well as network.

Issue-URL: #1086.

src/System.IO.FileSystem/src/System/IO/Directory.cs

@@ -115,7 +115,41 @@ public static DateTime GetCreationTimeUtc(String path)
         {
             return File.GetCreationTimeUtc(path);
         }
-
+
+        // Gets actual casing of path. The result is string with exact path
+        // as disk or network.
+        //
+        // Your application must have Read permissions to the directory.
+        //
+        public static string GetActualCasing(string path)
+        {
+            // TODO: Check permissions and throw SecurityException
+            //       once FIleIOPermissions is available on CoreFX.
+
+            StringBuilder builder = new StringBuilder(32767);
+
+            if (path.StartsWith(@"\\"))
+                path = @"\\?\UNC" + path.Substring(1);
+            else
+                path = @"\\?\" + path;
+
+            try
+            {
+                Interop.mincore.GetLongPathName(path, builder, builder.Capacity);
+
+                string returnedPathTrimmed = builder.Replace(@"\\?\UNC\", @"\\").Replace(@"\\?\", "").ToString();
+
+                if (Directory.Exists(returnedPathTrimmed))
+                    return returnedPathTrimmed;
+                else
+                    throw new Exception();
+            }
+            catch (Exception)
+            {
+                throw new DirectoryNotFoundException();
+            }
+        }
+
         public static void SetLastWriteTime(String path, DateTime lastWriteTime)
         {
             String fullPath = PathHelpers.GetFullPathInternal(path);
@@ -604,4 +638,3 @@ public static void Delete(String path, bool recursive)
         }
     }
 }
-

src/System.IO.FileSystem/src/System/IO/File.cs

@@ -2,6 +2,7 @@
 // Licensed under the MIT license. See LICENSE file in the project root for full license information.
 
 using System;
+using System.Linq;
 using System.Runtime.InteropServices;
 using System.Collections.Generic;
 using System.Diagnostics;
@@ -150,7 +151,7 @@ public static FileStream Create(String path, int bufferSize, FileOptions options
             return new FileStream(path, FileMode.Create, FileAccess.ReadWrite,
                                   FileShare.None, bufferSize, options);
         }
- 
+
         // Deletes a file. The file specified by the designated path is deleted.
         // If the file does not exist, Delete succeeds without throwing
         // an exception.
@@ -329,6 +330,46 @@ public static FileAttributes GetAttributes(String path)
             return FileSystem.Current.GetAttributes(fullPath);
         }
 
+        // Gets actual casing of path. The result is string with exact path
+        // as disk or network.
+        //
+        // Your application must have Read permission to the file.
+        //
+        public static string GetActualCasing(string path)
+        {
+            // TODO: Check permissions and throw SecurityException
+            //       once FIleIOPermissions is available on CoreFX.
+
+            StringBuilder builder = new StringBuilder(32767);
+
+            if (path.StartsWith(@"\\"))
+                path = @"\\?\UNC" + path.Substring(1);
+            else
+                path = @"\\?\" + path;
+
+            try
+            {
+                Interop.mincore.GetLongPathName(path, builder, builder.Capacity);
+
+                string returnedPathTrimmed = builder.Replace(@"\\?\UNC\", @"\\").Replace(@"\\?\", "").ToString();
+
+                if (Directory.Exists(returnedPathTrimmed))
+                    throw new Exception();
+
+                // unfortunately, the file part is not corrected by GetLongPathName
+                FileInfo fileInfo = new FileInfo(returnedPathTrimmed);
+
+                return fileInfo.Directory
+                      .GetFileSystemInfos()
+                      .FirstOrDefault(s => s.FullName.Equals(fileInfo.FullName, StringComparison.CurrentCultureIgnoreCase))
+                      .FullName;
+            }
+            catch (Exception)
+            {
+                throw new FileNotFoundException();
+            }
+        }
+
         [System.Security.SecurityCritical]
         public static void SetAttributes(String path, FileAttributes fileAttributes)
         {

src/System.IO.FileSystem/src/project.json

@@ -7,6 +7,7 @@
     "System.Globalization": "4.0.10-beta-*",
     "System.IO": "4.0.10-beta-*",
     "System.IO.FileSystem.Primitives": "4.0.0-beta-*",
+    "System.Linq": "4.0.0-beta-*",
     "System.Reflection": "4.0.10-beta-*",
     "System.Reflection.Primitives": "4.0.0-beta-*",
     "System.Resources.ResourceManager": "4.0.0-beta-*",

src/System.IO.FileSystem/src/project.lock.json

@@ -82,6 +82,21 @@
           "lib/dotnet/System.IO.FileSystem.Primitives.dll": {}
         }
       },
+      "System.Linq/4.0.0-beta-23024": {
+        "dependencies": {
+          "System.Runtime": "4.0.20-beta-23024",
+          "System.Collections": "4.0.10-beta-23024",
+          "System.Resources.ResourceManager": "4.0.0-beta-23024",
+          "System.Diagnostics.Debug": "4.0.10-beta-23024",
+          "System.Runtime.Extensions": "4.0.10-beta-23024"
+        },
+        "compile": {
+          "ref/dotnet/System.Linq.dll": {}
+        },
+        "runtime": {
+          "lib/dotnet/System.Linq.dll": {}
+        }
+      },
       "System.Private.Uri/4.0.0-beta-23024": {
         "runtime": {
           "lib/DNXCore50/System.Private.Uri.dll": {}

src/System.IO.FileSystem/tests/Directory/GetActualCasing.cs

@@ -0,0 +1,37 @@
+// Copyright (c) Microsoft. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+using System;
+using System.IO;
+using Xunit;
+
+public class Directory_GetActualPath
+{
+    [Theory]
+    [PlatformSpecific(PlatformID.Windows)]
+    [InlineData(TestInfo.CurrentDirectory)]
+    [InlineData(@"\\localhost\" + TestInfo.CurrentDirectory.Replace(':', '$'))]
+    public static void TrueCasingTest_Truthy(string path)
+    {
+        Assert.Equal(path, Directory.GetActualCasing(path.ToUpper()));
+    }
+
+    [Theory]
+    [PlatformSpecific(PlatformID.Windows)]
+    [InlineData(Environment.SystemDirectory)]
+    [InlineData(Environment.SystemDirectory.ToUpper())]
+    public static void TrueCasingTest_Falsy(string path)
+    {
+        Assert.NotEqual(path, Directory.GetActualCasing(path));
+    }
+
+    [Theory]
+    [PlatformSpecific(PlatformID.Windows)]
+    [InlineData(@"\\rand0m-server\devnul")]
+    [InlineData(Environment.SystemDirectory + @"\KERNEL32.DlL")]
+    [InlineData(Environment.SystemDirectory + @"\RANDOM-NON_EXISTING-Slug\")]
+    public static void TrueCasingTest_Throwy(string path)
+    {
+        Assert.Throws(typeof(DirectoryNotFoundException), Directory.GetActualCasing(path));
+    }
+}

src/System.IO.FileSystem/tests/File/GetActualCasing.cs

@@ -0,0 +1,44 @@
+// Copyright (c) Microsoft. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+using System;
+using System.IO;
+using Xunit;
+
+public class File_GetActualPath
+{
+    [Fact]
+    [PlatformSpecific(PlatformID.Windows)]
+    public static void TrueCasingTest_Truthy()
+    {
+        string unicodedFileName = Path.Combine(TestInfo.CurrentDirectory, "тратата.text.txt");
+
+        File.Create(unicodedFileName).Dispose();
+
+        Assert.Equal(unicodedFileName, File.GetActualCasing(unicodedFileName.ToUpper()));
+
+        File.Delete(unicodedFileName);
+
+        string path = @"\\localhost\" + Environment.SystemDirectory.Replace(':', '$') + @"\kernel32.dll";
+
+        Assert.Equal(path, File.GetActualCasing(path.ToUpper()));
+    }
+
+    [Theory]
+    [PlatformSpecific(PlatformID.Windows)]
+    [InlineData(Environment.SystemDirectory + @"\KERNEL32.DlL")]
+    [InlineData(Environment.SystemDirectory.ToUpper() + @"\kernel32.dll")]
+    public static void TrueCasingTest_Falsy(string path)
+    {
+        Assert.NotEqual(path, File.GetActualCasing(path));
+    }
+
+    [Theory]
+    [PlatformSpecific(PlatformID.Windows)]
+    [InlineData(@"\\rand0m-server\devnul\blah.txt")]
+    [InlineData(Environment.SystemDirectory + @"\RANDOM-NON_EXISTING-Slug\KERNEL32_INVALID.DlL")]
+    public static void TrueCasingTest_Throwy(string path)
+    {
+        Assert.Throws(typeof(FileNotFoundException), File.GetActualCasing(path));
+    }
+}

src/System.IO.FileSystem/tests/System.IO.FileSystem.Tests.csproj

@@ -37,6 +37,7 @@
     <Compile Include="DirectoryInfo\Delete.cs" />
     <Compile Include="DirectoryInfo\Delete_bool.cs" />
     <Compile Include="DirectoryInfo\Exists.cs" />
+    <Compile Include="Directory\GetActualCasing.cs" />
     <Compile Include="FileStream\Flush.Sharing.cs" />
     <Compile Include="FileStream\Flush_toDisk.cs" />
     <Compile Include="FileStream\SafeFileHandle.cs" />
@@ -72,6 +73,7 @@
     <Compile Include="FileStream\ctor_str_fm_fa_fs.cs" />
     <Compile Include="FileStream\ctor_str_fm_fa.cs" />
     <Compile Include="FileStream\ctor_str_fm.cs" />
+    <Compile Include="File\GetActualCasing.cs" />
     <Compile Include="UnseekableFileStream.cs" />
     <Compile Include="FSAssert.cs" />
     <Compile Include="FileSystemTest.cs" />