System.IO work planned for .NET 7

[jeffhandley]

This issue captures the planned work for .NET 7. This list is expected to change throughout the release cycle according to ongoing planning and discussions, with possible additions and subtractions to the scope.

Summary

We invested heavily in System.IO during .NET 6. During .NET 7, we will continue to make improvements to this area. We will address issues with the FileStream rewrite (#40359) and Symbolic Links, and we will make improvements to System.IO.Stream. At the top of the backlog after .NET 7 are investments such more enhancements to the Symbolic Links introduced in .NET 6, stabilizing more tests, and possibly introducing new APIs related to globbing.

Planned for .NET 7

• Symbolic Links
  • broken symlinks and non-executable files not ignored in FindProgramInPath() #29940
  • Cannot change LastWriteTime or LastAccessTime of a symlink #38824
• FileStream
  • Remove Net5CompatFileStreamStrategy in .NET 7 early previews #55196
  • .NET 6 FileStream fails with System.IO.IOException: 'The parameter is incorrect' when FILE_FLAG_NO_BUFFERING used  #62851
  • FileStream.Handle is obsolete in .NET6 too. dotnet-api-docs#7455
• Provide a version of Stream.Read that reads as much as possible #16598
• Remove Microsoft.IO.Redist. #58359
• File.ReadAllBytes* should support non-seekable files #58383
• File.SetLastWrite time fails on readonly files on Windows #62602
• [API Proposal]: Introduce RandomAccess.SetLength(SafeFileHandle handle) method #58376
• Add CancellationToken to StreamReader.Read* methods #20824
• FileSystemEventArgs.FullPath does not return a fully qualified path #62606
• DirectoryInfo.MoveTo mistakenly prevents renaming directories to case variations of themselves on Windows, macOS #63287
• Test failed: System.IO.Tests.EncryptDecrypt.EncryptDecrypt_Read #12339
• System.IO.Tests getting killed (OOM?) for Libraries Test Run release mono Linux arm64 Debug #56165
• [wasm][aot] Windows: Test failures for System.IO.FileSystem.Tests #58707
• Getting error on windows => System.PlatformNotSupportedException: 'System.IO.Ports is currently only supported on Windows.' #25375
• Creating symbolic links without developer mode or elevation fails silently #62975

Backlog (roughly in priority order)

• Canonical paths / real file casing / real path:
  • Proposed API for canonical paths #23871
  • Add API to get actual file casing in path #14321
  • Request: a way to tell if two filepaths point to the same file #17873
• Symbolic Links
  • API Proposal: tell if a filesystem entry is any type of link #53577
  • Allow opting out of following directory links (reparse points / symlinks) during recursive file-system enumerations #52666
  • System.IO: Allow recursive file system enumeration to continue when directory link's target does not exist #58612
  • FileInfo/DirectoryInfo: enable transparent handling of symbolic links #52908
  • Expose reparse point tags #1908
  • Mac SDK: DirectoryInfo.EnumerateDirectories and DirectoryInfo.EnumerateFiles Method does not handle symbolic link very well #34363
  • NTFS volume on Linux - junction does not work properly #20874
• Test Stabilization
  • System.IO.Tests.File_ReadWriteAllBytes.ReadAllBytes_NonSeekableFileStream_InWindows failed #60427
  • FileSystemWatcher_DirectorySymbolicLink_TargetsFile_Fails #53366
  • CopyToNanosecondsPresent_LowTempRes  #48717
  • Test failed: System.IO.Tests.File_Create_Tests.FileSystemWatcher_File_Create_EnablingDisablingNotAffectRaisingEvent #32955
  • [iOS/tvOS] System.IO.FileSystem.DriveInfoTests.DriveInfoUnixTests.TestGetDrives fails on devices #60586
  • [browser][io][tests] Failure: System.IO.Tests file for 2GB file reads #45954
  • New DeviceInterfaceCanBeOpenedForAsyncIO test fails deterministically locally #56681
• FileStream
  • Use FileStream buffering only when it makes sense #51048
  • No details for FileStream.Close dotnet-api-docs#1041
  • Docs for FileStream constructors are confusing about accessing devices dotnet-api-docs#1124
  • FileStream example bug dotnet-api-docs#4141
• Browser compat: Stream class using unsupported API #44543
• Memory Mapped files access control classes missing in dotnet core #48793
• Developers can enumerate directories and files using globbing patterns #21362
• Add Path.RemoveRelativeSegments Api #2162
• Identify places where file handles are closed and very soon reopened again #64288
• Proposal: using ArrayPool<byte> in MemoryStream with new APIs #22428
• StreamReader.ReadLineAsync performance can be improved #62061
• SerialPort - high CPU usage  #2379
• Consider removing Stream's semaphore #45089
• Relax RandomAccess type requirements, make all Read*|Write* methods work with non-seekable files #58381
• Remove ! from Microsoft.Extensions.FileSystemGlobbing #58211

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Issue Details

---

This issue captures the planned work for .NET 7. This list is expected to change throughout the release cycle according to ongoing planning and discussions, with possible additions and subtractions to the scope.

Summary

We invested heavily in System.IO during .NET 6. During .NET 7, we will continue to make improvements to this area. We will address issues introduced by the FileStream rewrite (#40359), make incremental enhancements to the Symbolic Link APIs introduced in .NET 6, make improvements to System.IO.Stream, stabilize more tests, and possibly introduce new APIs related to globbing.

Planned for .NET 7

Symbolic Link and System.IO Stream plans are captured in their own epics:

• System.IO Symbolic Link work planned for .NET 7 #57205
• System.IO.Stream Backlog #58216

FileStream

We will address issues and respond to feedback related to the substantial FileStream work completed in .NET 6 (#40359).

• Remove Net5CompatFileStreamStrategy in .NET 7 early previews #55196
• .NET 6 FileStream fails with System.IO.IOException: 'The parameter is incorrect' when FILE_FLAG_NO_BUFFERING used  #62851
• Use FileStream buffering only when it makes sense #51048
• No details for FileStream.Close dotnet-api-docs#1041
• Docs for FileStream constructors are confusing about accessing devices dotnet-api-docs#1124
• FileStream example bug dotnet-api-docs#4141
• FileStream.Handle is obsolete in .NET6 too. dotnet-api-docs#7455

Test Stabilization

• Test failed: System.IO.Tests.EncryptDecrypt.EncryptDecrypt_Read #12339
• System.IO.Tests.File_ReadWriteAllBytes.ReadAllBytes_NonSeekableFileStream_InWindows failed #60427
• FileSystemWatcher_DirectorySymbolicLink_TargetsFile_Fails #53366
• CopyToNanosecondsPresent_LowTempRes  #48717
• Test failed: System.IO.Tests.File_Create_Tests.FileSystemWatcher_File_Create_EnablingDisablingNotAffectRaisingEvent #32955
• [Android] Test failure: System.IO.Tests.Enumeration.RootTests.CanRecurseFromRoot #55822
• System.IO.Tests getting killed (OOM?) for Libraries Test Run release mono Linux arm64 Debug #56165
• [iOS/tvOS] System.IO.FileSystem.DriveInfoTests.DriveInfoUnixTests.TestGetDrives fails on devices #60586
• [browser][io][tests] Failure: System.IO.Tests file for 2GB file reads #45954
• [wasm][aot] Windows: Test failures for System.IO.FileSystem.Tests #58707
• New DeviceInterfaceCanBeOpenedForAsyncIO test fails deterministically locally #56681

Fixes and Enhancements

• Remove Microsoft.IO.Redist. #58359
• File.ReadAllBytes* should support non-seekable files #58383
• File.SetLastWrite time fails on readonly files on Windows #62602
• [API Proposal]: Introduce RandomAccess.SetLength(SafeFileHandle handle) method #58376
• Add CancellationToken to StreamReader.Read* methods #20824
• Add Cross DAC documentation #54498
• FileSystemEventArgs.FullPath does not return a fully qualified path #62606
• DirectoryInfo.MoveTo mistakenly prevents renaming directories to case variations of themselves on Windows, macOS #63287
• Browser compat: Stream class using unsupported API #44543
• Memory Mapped files access control classes missing in dotnet core #48793
• Developers can enumerate directories and files using globbing patterns #21362

Under Consideration

The following items are still under consideration for .NET 7; a small number of these may be included in .NET 7.

• Canonical paths / real file casing / real path:
  • Proposed API for canonical paths #23871
  • Add API to get actual file casing in path #14321
  • Request: a way to tell if two filepaths point to the same file #17873
• Add Path.RemoveRelativeSegments Api #2162
• Identify places where file handles are closed and very soon reopened again #64288
• Proposal: using ArrayPool<byte> in MemoryStream with new APIs #22428
• Getting error on windows => System.PlatformNotSupportedException: 'System.IO.Ports is currently only supported on Windows.' #25375
• StreamReader.ReadLineAsync performance can be improved #62061
• SerialPort - high CPU usage  #2379
• Consider removing Stream's semaphore #45089
• Relax RandomAccess type requirements, make all Read*|Write* methods work with non-seekable files #58381
• Remove ! from Microsoft.Extensions.FileSystemGlobbing #58211

Author:	jeffhandley
Assignees:	jeffhandley, adamsitnik, Jozkee
Labels:	Epic, area-System.IO, Priority:3, Team:Libraries
Milestone:	7.0.0

[jeffhandley]

This list in this issue has been edited to reflect changes from our ongoing planning and discussions. The headings have been updated to reflect what is still planned for .NET 7 and what is in the backlog. The list is still expected to change throughout the release cycle with periodic reviews of our plans.

Additionally, the items from System.IO Symbolic Link work planned for .NET 7 · Issue #57205 · dotnet/runtime have been merged into this issue.

[iSazonov]

Can we include #1953 too?