install_profile_info() removes required module instead of profile module from dependencies

Was that an RTBC? :)

FWIW, even though I'd have an idea for testing this, that would be an extremely narrow DUTB test, which would only test for this particular bug... — Therefore, I thought it wouldn't be worth to add that test here.

Instead of such a too narrow test, I think we need to (1) revamp the architecture of install profile [info] and (2) introduce proper test coverage as part of #2186491: [meta] D8 Extension System: Discovery/Listing/Info

That is, because only after cowboy-debugging this via debug_backtrace(), I learned that the entire surrounding code is some giant plate of spaghetti, sans sauce.

When stepping through this with a debugger, note that you might need an actual distribution profile in your filesystem.

The code path is triggered by install_begin_request() on line 392:

  if ($profile = _install_select_profile($install_state)) {
    $install_state['parameters']['profile'] = $profile;

Where _install_select_profile() performs:

  foreach ($install_state['profiles'] as $profile) {
    $profile_info = install_profile_info($profile->getName());

install_profile_info() calls into drupal_required_modules(), which contains:

  // Unless called by the installer, an installation profile is required and
  // must always be loaded. drupal_get_profile() also returns the installation
  // profile in the installer, but only after it has been selected.
  if ($profile = drupal_get_profile()) {
    $required[] = $profile;
  }

→ But as visible in the first snippet, the 'profile' parameter is not set yet, so drupal_get_profile() returns no profile name and thus the resulting list does not contain a profile.

Instead, the first element in the returned array is simply the first 'required' module that has been discovered.

distro.profile-info-required.0.patch queued for re-testing.