ping?

I already tested this in the past, and while it seemed to do what it is supposed to do, I was unsure at the time whether I considered all implications and tested all edge cases.
However, this has waiting for long enough already. Let's merge it as-is, I'm sure the edge cases will show themselves on their own accord then... ;)

Thanks for the PR, @drzraf !

@schlessera This actually had some test failures, see https://github.com/wp-cli/wp-cli/actions/runs/13191576733/job/36825712748#step:11:295 for example

@drzraf @schlessera Unfortunately I had to temporarily revert this in #6049 because of a test failure. But we can try to land it again.

Can't reproduce the failure locally: composer behat -- features/flags.feature passes

16 scenarios (16 passed)
98 steps (98 passed)
0m27.49s (11.38Mb)

and the full run gives

233 scenarios (228 passed, 5 failed)
2416 steps (2390 passed, 5 failed, 21 skipped)
11m39.65s (11.97Mb)

but none of these 5 failures matches those mentioned by the CI

The problem is that in the CI it is setting the -i flag (from the new code in this PR), which you can see in the failed test:

  Debug (bootstrap): Running SSH command: docker exec --user 'user' -i 'wordpress' sh -c 'wp '\''--debug'\'' '\''--version'\''' (0.074s)

But the test does not expect that new -i:

The tests pass locally because
$is_stdin_tty = function_exists( 'posix_isatty' ) ? posix_isatty( STDIN ) : true;
Will return true because STDIN is attached to your local terminal which is a TTY.

You can reproduce the CI failure by piping the test through cat which will remove the tty:

composer behat -- features/flags.feature:357 | cat

FWIW I think the double negative here is a bit confusing and hard to follow

! $is_stdin_tty && ! getenv( 'WP_CLI_DOCKER_NO_INTERACTIVE' ) ? '-i ' : ''

The test should probably be updated and include the environment variables so the output is the same across local and ci testing. I think otherwise it would require creating a new custom step to check for tty if we really wanted to test the tty detection as well.