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Use a real rename for File.Move(overwrite) polyfill #664

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Merged
SimonCropp merged 1 commit into from
Oct 11, 2026
Merged

Use a real rename for File.Move(overwrite) polyfill #664

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144 changes: 135 additions & 9 deletions src/Polyfill/FilePolyfill.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -3,6 +3,7 @@ namespace Polyfills;
using System;
using System.IO;
using System.Collections.Generic;
using System.ComponentModel;
using System.Diagnostics;
using System.Diagnostics.CodeAnalysis;
using System.Text;
Expand Down Expand Up @@ -132,20 +133,12 @@ public static Task AppendAllBytesAsync(string path, ReadOnlyMemory<byte> bytes,
//Link: https://learn.microsoft.com/en-us/dotnet/api/system.io.file.move?view=net-11.0#system-io-file-move(system-string-system-string-system-boolean)
public static void Move(string sourceFileName, string destFileName, bool overwrite)
{
sourceFileName = Path.GetFullPath(sourceFileName);
destFileName = Path.GetFullPath(destFileName);
if (sourceFileName == destFileName)
{
return;
}

#if NETCOREAPP3_0_OR_GREATER
File.Move(sourceFileName, destFileName, overwrite: overwrite);
#else
if (overwrite)
{
File.Copy(sourceFileName, destFileName, overwrite: true);
File.Delete(sourceFileName);
FileMoveHelper.MoveAndOverwrite(sourceFileName, destFileName);
}
else
{
Expand Down Expand Up @@ -379,6 +372,139 @@ public static async IAsyncEnumerable<string> ReadLinesAsync(string path, Encodin
#endif

}

#if !NETCOREAPP3_0_OR_GREATER
[ExcludeFromCodeCoverage]
[DebuggerNonUserCode]
#if PolyUseEmbeddedAttribute
[global::Microsoft.CodeAnalysis.EmbeddedAttribute]
#endif
static class FileMoveHelper
{
const uint MOVEFILE_REPLACE_EXISTING = 1;
const uint MOVEFILE_COPY_ALLOWED = 2;

const int ERROR_FILE_NOT_FOUND = 2;
const int ERROR_PATH_NOT_FOUND = 3;
const int ERROR_ACCESS_DENIED = 5;

const int EPERM = 1;
const int ENOENT = 2;
const int EACCES = 13;
const int EXDEV = 18;

// A rename that replaces the destination, as File.Move(string, string, bool) does on netcoreapp3.0 and up.
internal static void MoveAndOverwrite(string sourceFileName, string destFileName)
{
ValidatePath(sourceFileName, nameof(sourceFileName));
ValidatePath(destFileName, nameof(destFileName));

var source = Path.GetFullPath(sourceFileName);
var dest = Path.GetFullPath(destFileName);

if (!File.Exists(source))
{
throw new FileNotFoundException($"Could not find file '{source}'.", source);
}

#if FeatureRuntimeInformation
if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows))
#else
if (Environment.OSVersion.Platform == PlatformID.Win32NT)
#endif
{
if (!MoveFileExW(ToExtendedPath(source), ToExtendedPath(dest), MOVEFILE_REPLACE_EXISTING | MOVEFILE_COPY_ALLOWED))
{
throw CreateWindowsException(Marshal.GetLastWin32Error(), source);
}

return;
}

if (rename(source, dest) == 0)
{
return;
}

var error = Marshal.GetLastWin32Error();
if (error == EXDEV)
{
// rename does not cross file systems
File.Copy(source, dest, overwrite: true);
File.Delete(source);
return;
}

throw CreateUnixException(error, source, dest);
}

static void ValidatePath(string path, string paramName)
{
if (path is null)
{
throw new ArgumentNullException(paramName);
}

if (path.Length == 0)
{
throw new ArgumentException("The value cannot be an empty string.", paramName);
}
}

// MoveFileEx is limited to MAX_PATH unless the path has the extended prefix
static string ToExtendedPath(string fullPath)
{
if (fullPath.Length < 260 ||
fullPath.StartsWith(@"\\?\", StringComparison.Ordinal))
{
return fullPath;
}

if (fullPath.StartsWith(@"\\", StringComparison.Ordinal))
{
return @"\\?\UNC\" + fullPath.Substring(2);
}

return @"\\?\" + fullPath;
}

static Exception CreateWindowsException(int error, string source)
{
switch (error)
{
case ERROR_FILE_NOT_FOUND:
return new FileNotFoundException($"Could not find file '{source}'.", source);
case ERROR_PATH_NOT_FOUND:
return new DirectoryNotFoundException("Could not find a part of the path.");
case ERROR_ACCESS_DENIED:
return new UnauthorizedAccessException("Access to the path is denied.");
default:
return new IOException(new Win32Exception(error).Message, unchecked((int) 0x80070000) | error);
}
}

static Exception CreateUnixException(int error, string source, string dest)
{
switch (error)
{
case ENOENT:
// the source exists, so it is the destination directory that is missing
return new DirectoryNotFoundException("Could not find a part of the path.");
case EPERM:
case EACCES:
return new UnauthorizedAccessException("Access to the path is denied.");
default:
return new IOException($"Unable to move file '{source}' to '{dest}'.", error);
}
}

[DllImport("kernel32.dll", EntryPoint = "MoveFileExW", CharSet = CharSet.Unicode, SetLastError = true)]
static extern bool MoveFileExW(string lpExistingFileName, string lpNewFileName, uint dwFlags);

[DllImport("libc", SetLastError = true)]
static extern int rename(string oldpath, string newpath);
}
#endif
#endif

#if !NET11_0_OR_GREATER
Expand Down
1 change: 1 addition & 0 deletions src/Split/net10.0/FilePolyfill.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -4,6 +4,7 @@ namespace Polyfills;
using System;
using System.IO;
using System.Collections.Generic;
using System.ComponentModel;
using System.Diagnostics;
using System.Diagnostics.CodeAnalysis;
using System.Text;
Expand Down
1 change: 1 addition & 0 deletions src/Split/net11.0/FilePolyfill.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -4,6 +4,7 @@ namespace Polyfills;
using System;
using System.IO;
using System.Collections.Generic;
using System.ComponentModel;
using System.Diagnostics;
using System.Diagnostics.CodeAnalysis;
using System.Text;
Expand Down
117 changes: 109 additions & 8 deletions src/Split/net461/FilePolyfill.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -4,6 +4,7 @@ namespace Polyfills;
using System;
using System.IO;
using System.Collections.Generic;
using System.ComponentModel;
using System.Diagnostics;
using System.Diagnostics.CodeAnalysis;
using System.Text;
Expand Down Expand Up @@ -102,16 +103,9 @@ public static Task AppendAllBytesAsync(string path, ReadOnlyMemory<byte> bytes,
/// </summary>
public static void Move(string sourceFileName, string destFileName, bool overwrite)
{
sourceFileName = Path.GetFullPath(sourceFileName);
destFileName = Path.GetFullPath(destFileName);
if (sourceFileName == destFileName)
{
return;
}
if (overwrite)
{
File.Copy(sourceFileName, destFileName, overwrite: true);
File.Delete(sourceFileName);
FileMoveHelper.MoveAndOverwrite(sourceFileName, destFileName);
}
else
{
Expand Down Expand Up @@ -286,6 +280,113 @@ public static async IAsyncEnumerable<string> ReadLinesAsync(string path, Encodin
}
#endif
}
[ExcludeFromCodeCoverage]
[DebuggerNonUserCode]
#if PolyUseEmbeddedAttribute
[global::Microsoft.CodeAnalysis.EmbeddedAttribute]
#endif
static class FileMoveHelper
{
const uint MOVEFILE_REPLACE_EXISTING = 1;
const uint MOVEFILE_COPY_ALLOWED = 2;
const int ERROR_FILE_NOT_FOUND = 2;
const int ERROR_PATH_NOT_FOUND = 3;
const int ERROR_ACCESS_DENIED = 5;
const int EPERM = 1;
const int ENOENT = 2;
const int EACCES = 13;
const int EXDEV = 18;
internal static void MoveAndOverwrite(string sourceFileName, string destFileName)
{
ValidatePath(sourceFileName, nameof(sourceFileName));
ValidatePath(destFileName, nameof(destFileName));
var source = Path.GetFullPath(sourceFileName);
var dest = Path.GetFullPath(destFileName);
if (!File.Exists(source))
{
throw new FileNotFoundException($"Could not find file '{source}'.", source);
}
#if FeatureRuntimeInformation
if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows))
#else
if (Environment.OSVersion.Platform == PlatformID.Win32NT)
#endif
{
if (!MoveFileExW(ToExtendedPath(source), ToExtendedPath(dest), MOVEFILE_REPLACE_EXISTING | MOVEFILE_COPY_ALLOWED))
{
throw CreateWindowsException(Marshal.GetLastWin32Error(), source);
}
return;
}
if (rename(source, dest) == 0)
{
return;
}
var error = Marshal.GetLastWin32Error();
if (error == EXDEV)
{
File.Copy(source, dest, overwrite: true);
File.Delete(source);
return;
}
throw CreateUnixException(error, source, dest);
}
static void ValidatePath(string path, string paramName)
{
if (path is null)
{
throw new ArgumentNullException(paramName);
}
if (path.Length == 0)
{
throw new ArgumentException("The value cannot be an empty string.", paramName);
}
}
static string ToExtendedPath(string fullPath)
{
if (fullPath.Length < 260 ||
fullPath.StartsWith(@"\\?\", StringComparison.Ordinal))
{
return fullPath;
}
if (fullPath.StartsWith(@"\\", StringComparison.Ordinal))
{
return @"\\?\UNC\" + fullPath.Substring(2);
}
return @"\\?\" + fullPath;
}
static Exception CreateWindowsException(int error, string source)
{
switch (error)
{
case ERROR_FILE_NOT_FOUND:
return new FileNotFoundException($"Could not find file '{source}'.", source);
case ERROR_PATH_NOT_FOUND:
return new DirectoryNotFoundException("Could not find a part of the path.");
case ERROR_ACCESS_DENIED:
return new UnauthorizedAccessException("Access to the path is denied.");
default:
return new IOException(new Win32Exception(error).Message, unchecked((int) 0x80070000) | error);
}
}
static Exception CreateUnixException(int error, string source, string dest)
{
switch (error)
{
case ENOENT:
return new DirectoryNotFoundException("Could not find a part of the path.");
case EPERM:
case EACCES:
return new UnauthorizedAccessException("Access to the path is denied.");
default:
return new IOException($"Unable to move file '{source}' to '{dest}'.", error);
}
}
[DllImport("kernel32.dll", EntryPoint = "MoveFileExW", CharSet = CharSet.Unicode, SetLastError = true)]
static extern bool MoveFileExW(string lpExistingFileName, string lpNewFileName, uint dwFlags);
[DllImport("libc", SetLastError = true)]
static extern int rename(string oldpath, string newpath);
}
extension(File)
{
/// <summary>
Expand Down
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