Use 'wslview' instead of 'xdg-open' on Windows

[maxim-belkin]

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In WSL, xdg-open is not available -- wslview is. So, added wsl? and wsl_version methods to OS::Linux to conditionally set PATH_OPEN

Additional "require" statements:

• require "PATH" in utils.rb: needed by PATH.new in which
• require "utils" in linux.rb: needed by which in os_version
• require "version" in os.rb: needed by sig { returns(Version) }

To test, execute brew docs

[BrewTestBot]

Review period will end on 2023-02-28 at 08:36:59 UTC.

[BrewTestBot]

Review period skipped due to critical label.

[MikeMcQuaid]

Makes sense to me, thanks @maxim-belkin! Some brew style failures but happy to land this after those: https://github.com/Homebrew/brew/actions/runs/4280813376/jobs/7453043805

[maxim-belkin]

Thank you, Mike, for approving the pull request!

[MikeMcQuaid]

@maxim-belkin some more brew style --fix needed and then should be good to go!

[MikeMcQuaid]

Thanks again @maxim-belkin!

[maxim-belkin]

Thanks for the review and feedback, Mike!

[RandomDSdevel]

@maxim-belkin, CC @MikeMcQuaid:

     A Linux distribution installed inside Windows Subsystem for Linux v2 isn't guaranteed not to have 'xdg-open' available. Also, custom WSL distributions created manually by a user instead of downloaded from the Microsoft Store aren't guaranteed to have 'wslview' in their 'PATH.' For example, I don't have Homebrew installed on it — I'm perfectly happy with Portage there, though that isn't relevant for a Homebrew issue —, but I use a custom Gentoo WSL installation I made myself and can run graphical applications from inside it using its KDE Plasma installation and X410. Here's what I see in terminal sessions:

… ~ $ which xdg-open
/usr/bin/xdg-open
… ~ $ which wslview
which: no wslview in (~/.local/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/opt/bin:/usr/lib/llvm/15/bin)

This kind of edge case might not be worth handling, at least not yet/at the moment, though?

[maxim-belkin]

Oh, I wasn't aware of such setups. It shouldn't be difficult to check if wslview or xdg-open is available in WSL.

[MikeMcQuaid]

@maxim-belkin Yeh, a follow-up PR to use which would be nice and just fallback?

[maxim-belkin]

@maxim-belkin Yeh, a follow-up PR to use which would be nice and just fallback?

Sure. We can do something like this (added "echo" in case wslview/xdg-open aren't available):

PATH_OPEN = ((which("wslview") || which("xdg-open")).to_s || "echo").freeze

or like this:

PATH_OPEN = ((OS::Linux.wsl? && k=which("wslview")) ? k.to_s : (k=which("xdg-open")) ? k.to_s : "echo").freeze

or like this:

PATH_OPEN = OS::Linux.wsl? && which("wslview").present? && which("wslview").to_s.freeze
PATH_OPEN ||= which("xdg-open").present? && which("xdg-open").to_s.freeze
PATH_OPEN ||= "echo".freeze

[MikeMcQuaid]

added "echo" in case wslview/xdg-open aren't available

I don't think that's necessary, no-one has ever mentioned that case.

How about:

PATH_OPEN = if OS::Linux.wsl? && (wslview = which("wslview").presence)
  wslview.to_s.freeze
else
  "xdg-open"
end

to best balance simplicity, current logic, existing logic and avoid handling corner cases no-one has ever reported