file: URLs on UNC shares are not supported

[shauniv]

Windows Terminal version

1.21.3231.0

Windows build number

10.0.26100.2894

Other Software

No response

Steps to reproduce

1. Output a formatted file URL for a file stored on a UNC network share. e.g. file://qnap-fs/dvd/test.txt
2. Note that there is an underline beneath the URL when you mouse hovers over it
3. Ctrl+Left mouse click the URL

Expected Behavior

1. The associated program runs with the file as an argument, or the Open With dialog pops up

Actual Behavior

1. An unhelpful error message appears:

2. Sometimes the mouse pointer disappears, and the "Cancel" button doesn't appear to be keyboard accessible, making it hard to dismiss this dialog.

[shauniv]

Also, System.Diagnostics.Process.Start() works just fine on such UNC URLs.

[DHowett]

You know, this is a weird one.

I recall writing this in #10188:

So this one is pretty curious. File URIs to UNC paths are poorly-specified. Terminals are recommended to reject file URIs that don't point back to the local host

I was trying to figure out where I got the recommendation from, and I couldn't find it. The closest I could come up with was https://gist.github.com/egmontkob/eb114294efbcd5adb1944c9f3cb5feda#file-uris-and-the-hostname.

We may want to reevaluate our position here...

[zadjii-msft]

There was also long discussion around here: #7668 (comment)