[.NET 6] UriBuilder breaking change not documented

[filipnavara]

Consider the following code:

Console.WriteLine(new UriBuilder("msg", "dummy", 0, "segment").Uri);

On .NET 5 the output is msg://dummy/segment. On .NET 6 the output is msg://dummy:0/segment. It is possible to change the port number to -1 to get the same result. This is not listed in the documented breaking changes. If it was intentional it should be added in there.

[dotnet-issue-labeler]

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[marek-safar]

/cc @karelz

[karelz]

@MihaZupan any thoughts?

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Issue Details

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Consider the following code:

Console.WriteLine(new UriBuilder("msg", "dummy", 0, "segment").Uri);

On .NET 5 the output is msg://dummy/segment. On .NET 6 the output is msg://dummy:0/segment. It is possible to change the port number to -1 to get the same result. This is not listed in the documented breaking changes. If it was intentional it should be added in there.

Author:	filipnavara
Assignees:	-
Labels:	area-System.Net, untriaged
Milestone:	-

[MihaZupan]

Introduced by #40986 which was a bug fix for #37865 (comment).
As documented by UriBuilder.Port, -1 should be used to get the default port.

You were relying on an undocumented bug affecting unknown Uri schemes. For example if you use http instead of msg, you will see that the port is present in both 5.0 and 6.0.

The is not specific to UriBuilder, and we may choose to document it as a breaking change.

[karelz]

It seems to fall into the "technical breaking change" category -- it was misbehaving against docs and we fixed it.
Given that it is fairly corner case, I would recommend to close the issue until we see at least couple of more customers hitting it. If more folks hit it, we should document it as breaking change. Otherwise this issue + docs may be sufficient IMO.

[filipnavara]

Thanks for the analysis! I expected that the change was intentional but it was a bit tricky to find what what going on (the bug didn't manifest anywhere close to the UriBuilder usage). I filed a ticket because it was not listed in the breaking changes and I thought that people may run into it.

[karelz]

Triage: Closing as per above explantion - #61363 (comment)
We will document it if more customers hit it. Please reply here, or file new issue referencing this one if you are in that category.