Installation breaks when choosing a different language than english.

[markaspot]

Installing via drush and choosing english as language in the web installer works fine. Choosing another language lets the web installer fail with a "Drupal is already installed" error.

[markaspot]

Tracing this behaviour leads to the following error:

RuntimeException: Failed to start the session because headers have already been sent by "/app/vendor/symfony/http-foundation/Response.php" at line 412. in /app/vendor/symfony/http-foundation/Session/Storage/NativeSessionStorage.php on line 139 #0 /app/web/core/lib/Drupal/Core/Session/SessionManager.php(163): Symfony\Component\HttpFoundation\Session\Storage\NativeSessionStorage->start() #1 /app/web/core/lib/Drupal/Core/Session/SessionManager.php(118): Drupal\Core\Session\SessionManager->startNow() #2 /app/vendor/symfony/http-foundation/Session/Session.php(71): Drupal\Core\Session\SessionManager->start() #3 /app/web/core/includes/install.core.inc(1482): Symfony\Component\HttpFoundation\Session\Session->start() #4 /app/web/core/includes/install.core.inc(671): install_bootstrap_full(Array) #5 /app/web/core/includes/install.core.inc(549): install_run_task(Array, Array) #6 /app/web/core/includes/install.core.inc(117): install_run_tasks(Array) #7 /app/web/core/install.php(44): install_drupal(Object(Composer\Autoload\ClassLoader))

[markaspot]

This error can be reproduced only by choosing a different language

1. Empty the database
2. Run the installer again with the same language:

Result: Installationprocess starts as usual.

1. Empty the database.
2. Choose another "non-english" language.
   Result: Error can be reproduced.

[markaspot]

This has to be tested with a normal installer. Distros like Mark-a-Spot or Open Social skip the standard profile selector.

[markaspot]

By using the distribution key in the distro.info.yml file, the installer starts directly installing and downloading the translation. It seems that the immediate request for the translation files is causing the error.
web/core/includes/install.core.inc:1243

// Check for a distribution profile.
  foreach ($install_state['profiles'] as $profile) {
    $profile_info = install_profile_info($profile->getName());
    if (!empty($profile_info['distribution'])) {
      return $profile->getName();
    }
  }

[Crell]

Interesting. Good sleuthing! This sounds like it's worth opening a core bug about; even if the fix isn't in core (although I suspect it is), it's good to get the issue raised there and a broader audience may have more ideas on how to fix it.

[markaspot]

Thanks for your support, Larry. Your reference to the Open Social distro got me on the right track. We should reference this bug in their queue, too. Core Issue opened: https://www.drupal.org/project/drupal/issues/2942369