System check script issues on Windows

[jwoertink]

In a generated app, you get a script/system_check.cr which helps to ensure your app is setup and bootstrapped properly in development before booting. (e.g. if you need yarn to run your app, then ensure yarn is installed before trying to boot the app).

However, speaking of yarn, there's an issue on Windows.

The system_check runs this

lucky_cli/src/web_app_skeleton/script/system_check.cr.ecr

Lines 14 to 16 in 0d67c0a

	if command_not_found "yarn"
	print_error "Yarn is not installed\n See https://yarnpkg.com/lang/en/docs/install/ for install instructions."
	end

which checks for the existence of an executable yarn.

lucky_cli/src/web_app_skeleton/script/helpers/function_helpers.cr.ecr

Lines 20 to 22 in 0d67c0a

	def command_not_found(command : String) : Bool
	Process.find_executable(command).nil?
	end

This find_executable method will automatically append .exe to whatever command you pass in

https://github.com/crystal-lang/crystal/blob/bcff68af7e503648edcdfdea9ae6be1fa09b7c6b/src/process/executable_path.cr#L70-L79

This means it's actually looking for yarn.exe which doesn't exist. When you install node and yarn, yarn (as well as some other node related commands like pnpm, etc...) are just shell scripts. Even if yarn is installed properly, this will fail.

An alternate way to solve this could be to just run yarn -v and then check $?. That value seems to return 0 on Linux and True on Windows. I'd assume Process.run("yarn -v").normal_exit? would work, but it does feel a little hacky. I'm open to other ideas if anyone has any.