[Uri] Add UriScheme Properties: SSH, FTPS, SFTP, WS, WSS

[ArthurHNL]

Currently, the System.Uri class has static fields for the Scheme part of a URI of common protocols:

• UriSchemeFile
• UriSchemeFtp
• UriSchemeGopher
• UriSchemeHttp
• UriSchemeHttps
• UriSchemeMailto
• UriSchemeNetPipe
• UriSchemeNetTcp
• UriSchemeNews
• UriSchemeNntp

I, however, think that this list is out of date and that the following URI Schemes would be a good addition for the .NET 5 era:

• UriSchemeSsh = "ssh" for secure shell access.
• UriSchemeFtps = "ftps" and UriSchemeSftp = "sftp" for secure filetransfer.
• UriSchemeWs = "ws" and UriSchemeWss = "wss" for (secure) websockets.

UriSchemeTelnet = "telnet" might be considered for interaction with legacy systems.

Proposal

Extend the list of well-known Uri schemes with more commonly used schemes.

namespace System
{
    public class Uri
    {
        // Existing
        public static readonly string UriSchemeFile;
        public static readonly string UriSchemeFtp;
        public static readonly string UriSchemeGopher;
        public static readonly string UriSchemeHttp;
        public static readonly string UriSchemeHttps;
        public static readonly string UriSchemeMailto;
        public static readonly string UriSchemeNews;
        public static readonly string UriSchemeNntp;
        public static readonly string UriSchemeNetTcp;
        public static readonly string UriSchemeNetPipe;

        // Proposed
        public static readonly string UriSchemeWs;
        public static readonly string UriSchemeWss;
        public static readonly string UriSchemeSsh;
        public static readonly string UriSchemeTelnet;
        public static readonly string UriSchemeSftp; // SSH File Transfer Protocol
        public static readonly string UriSchemeFtps; // FTP over SSL
    }
}

[ghost]

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[scalablecory]

I'm okay with adding these APIs. We should look to see if any other common schemes could be added at the same time. @MihaZupan what do you think?

[MihaZupan]

I think it makes sense adding them.

Ws, Wss and Telnet already exist, just aren't publicly exposed.

The idea of this list of schemes is that Uri has built-in knowledge of them to provide validation and avoid an allocation of the scheme string when parsing.
Adding more validation to new schemes now would be a breaking change (likely acceptable), but we can at the very least avoid the scheme string allocation.

Should any other schemes be considered? data comes to mind.

[ArthurHNL]

IANA maintains a list of all official URI schemes. Surprisingly, ftps is not on the list, yet spotify and steam are.

[karelz]

So what is the value of these APIs? Just to save 1 memory allocation? Is it really worth it?

[MihaZupan]

So what is the value of these APIs? Just to save 1 memory allocation?

No, this is to provide a list of common well-known Uri schemes (akin to MediaTypeNames #1489).

Whether to use the optimization of saving the scheme allocation is completely up to Uri - an implementation detail that currently holds true for schemes in this list (and ws, wss, telnet).

[MihaZupan]

@ArthurHNL I've edited your post with the proposal template and the API has been added to the review backlog.

[terrajobst]

Video

• The names and API shape makes sense.
• The only concern that we have is whether supporting those schemes has any implications on other parts of URI, such as in UriParser and populating defaults, such as ports. Is there any extra work we'd be signing up to support those? If so, we may want to be more selective what we support. @dotnet/ncl, could you double check?

namespace System
{
    public partial class Uri
    {
        public static readonly string UriSchemeWs;
        public static readonly string UriSchemeWss;
        public static readonly string UriSchemeSsh;
        public static readonly string UriSchemeTelnet;
        public static readonly string UriSchemeSftp;
        public static readonly string UriSchemeFtps;
    }
}

[poke]

Hey, I just wanted to let you know that I began working on this in #43375. I’m still struggling a bit with the build system but will add tests later. I would be happy about some early feedback though!

[scalablecory]

Thanks @poke, let me assign the issue to you. Please ask questions if you have any!

[poke]

The PR was merged so this issue can be closed 😊

[MihaZupan]

Thanks!