mpd: add test & install example conf file

[DomT4]

Follow up to #39353. The test should ensure we catch the need to bump for icu4c in future.

[tdsmith]

Can this fail? Will we get an exception back if mpd terminates abnormally?

[DomT4]

Should do. If it doesn't launch correctly, say because it can't find the correct linked dylib it shouldn't start the process, and there shouldn't be anything to kill. I'll revert my icu4c tonight and then install mpd again and then upgrade icu4c and run the test and see if it blows up as intended.

[DomT4]

Garg. Test succeeds even when it shouldn't. Will have to try and find another way, if there is one.

[DomT4]

Alright, I don't know. We could go ugly and obvious as in:

  test do
    icu4c = Formula["icu4c"].opt_lib/"libicui18n.55.dylib"
    assert_match /#{icu4c}/, shell_output("otool -L #{bin}/mpd")
  end

But everyone involved, me, you, all of the maintainers aside you, etc are going to hate the test. It works, but I don't really want to do it. Going to cc @jacknagel in case he knows of any Ruby magic on this.

[xu-cheng]

Is this a server or similar? If so, can it be tested by curl? Also Process.kill/wait should be inside a ensure block.

[DomT4]

Yeah, kinda.

I tried testing it with curl but inside Homebrew it vomits permission denied messages at me. If I run the curl check outside of Homebrew, it works great. Inside the test do block? Failure, so much failure.

And yup, my bad on forgetting the ensure 😺.

[DomT4]

Turns out I'm an idiot. I forgot to tuck the curl check inside a begin block and that was causing the failure. This should actually fix Tim's concern earlier as well, because curl will fail if the server doesn't respond and that'll blow up the test, so we should catch future icu4c bumps needed - At least, that's the hope. Pushing now.

[xu-cheng]

Shouldn't it be:

test do
  begin
    pid = fork do
      exec "#{bin}/mpd --stdout --no-daemon --no-config"
    end
    sleep 2
    assert_match /OK MPD/, shell_output("curl localhost:6600")
  ensure
    Process.kill("SIGINT", pid)
    Process.wait(pid)
  end
end

[DomT4]

Seemingly, It can be either and works. Homebrew's internal use tends to prefer begin inside the fork do, formulae lean towards preferring the begin after the fork do 😐.

[DomT4]

Bot decided to crash on this last night. Green now.

[MikeMcQuaid]

Thanks again @DomT4!