Add async support to SftpClient and SftpFileStream by IgorMilavec · Pull Request #819 · sshnet/SSH.NET

IgorMilavec · 2021-05-04T09:14:34Z

Core async support requested by #153.

Added async support to BaseClient: (update 2021-05-11)

ConnectAsync

Added async support to SftpClient:

ListDirectoryAsync
GetStatusAsync
OpenAsync
DeleteFileAsync
RenameFileAsync
DownloadFileAsync
UploadFileAsync

Added async support to SftpFileStream:

OpenAsync
ReadAsync
WriteAsync
FlushAsync

Added net46 target to use async in .NET Framework.

This PR is intended to resolve#153.
This PR is intended to supersede #300 and #661.

vanillajonathan · 2021-05-11T10:02:53Z

+ {
+ throw;
+ }
+ catch (Exception)


Should the generic class Exception be caught here? Or something more specific?

Possibly, but I only reused the logic of sync versions of the functions at this time. When/if this is released, practice will show if any changes need to be made.

When FileMode is Create, I think we should just use Flags.CreateNewOrOpen | Flags.Truncate.
Let me run some checks later.

I can confirm that it's ok to just add Flags.CreateNewOrOpen | Flags.Truncate when mode is FileMode.Create.

vanillajonathan · 2021-05-11T10:06:49Z

+ if (count < 0)
+ throw new ArgumentOutOfRangeException("count");
+ if ((buffer.Length - offset) < count)
+ throw new ArgumentException("Invalid array range.");


Specify second parameter to ArgumentException, nameof(buffer).

I'm not sure about that, any of the three could be wrong, depending on the caller's intention. Anyhow, this is the same as the sync version, so we either need to change both or none...

vanillajonathan · 2021-05-11T10:09:46Z

+ /// <exception cref="SftpPermissionDeniedException">Permission to list the contents of the directory was denied by the remote host. <para>-or-</para> A SSH command was denied by the server.</exception>
+ /// <exception cref="SshException">A SSH error where <see cref="Exception.Message" /> is the message from the remote host.</exception>
+ /// <exception cref="ObjectDisposedException">The method was called after the client was disposed.</exception>
+ public async Task<IEnumerable<SftpFile>> ListDirectoryAsync(string path, CancellationToken cancellationToken)


Consider returning ICollection or IReadOnlyCollection rather than IEnumerable as per the Microsoft Guidelines for Collections.
DO use Collection or a subclass of Collection for properties or return values representing read/write collections.

This should be IAsyncEnumerable<SftpFile>. It's only supported on .NET 4.6.1 or higher.
For .NET 4.6.1 and .NET Standard 2.0, you need to add a reference to Microsoft.Bcl.AsyncInterfaces.

Then we need to remove FEATURE_TAP from netstandard1.3. Also, we take two "external" dependencies (AsyncInterfaces and Task.Extensions).
What if we leave this one as it is and add IAsyncEnumerable<SftpFile> EnumerateDirectoryAsync(...) for netstandard2.1+ ?

I won't let this block this merge request, but I still strongly consider changing this method to return IAsyncEnumerable<SftpFile>. I also don't like bringing in additional dependencies, but the alternative is not better.

schaveyt · 2021-09-25T13:46:11Z

Any chance this could also target .net5 or .net6 as well

IgorMilavec · 2021-09-29T15:41:36Z

The library already targets netstandard2.0, so you can reference it from net5 or net6 projects.
It would only be beneficial for the library to target net5+ if it would use any net5+ features, like Spans etc. But this is out of scope of this issue and this PR. IMO we should remove legacy targets (please see #665) before adding any modern code.

schaveyt · 2021-09-29T19:02:23Z

I did not connect those dots. Thank you for clarifying 👍

paulmaybee · 2021-10-22T17:22:09Z

This addition looks like it has a great deal of value. Is there a timetable or estimate for when the PR will be completed?

IgorMilavec · 2021-10-25T07:30:23Z

This PR if functionally complete IMO. It should also be stable, I have been running it in production since July. Now we need @drieseng to review and merge it.

drieseng · 2021-10-25T07:42:33Z

@IgorMilavec Thanks, I'll try to find time in the coming days.

IgorMilavec · 2021-11-04T16:37:41Z

Figured this is the last chance to modify UploadFileAsync signature before this becomes a breaking change... :)

IgorMilavec added 2 commits May 4, 2021 11:05

Add FEATURE_TAP and net46 target
ca1a59f

Add TAP async support to SftpClient and SftpFileStream
5f74049