No messages in install / template logic for $messages

@testbot: I'm sorry.

Disregard #4, cweagans kindly rerolled it, but against page.tpl.php instead of maintenance-page.tpl.php.

Dear testbot, here is a new patch, now with -p flag and unix line endings. Thank you for your patience :-)

LOL
@cweagans: I thought you went to sleep?

I still don't get it. Re-submitting cweagans' #6 to see if that does pass the test.

@yched: OK, so in that case, Minnelli was "wrong" all this time for not checking for the $show_messages variable? Anyway, if the check for $show_messages is needed, we should set $show_messages = TRUE for the installation process.

I'm probably missing something, but here is what I don't understand:
The code in template_preprocess_maintenance_page() means that $message will only have a value (and return TRUE in an if statement) if $show_messages is TRUE.
In that case, this line of code in maintenance-page.tpl.php
<?php if ($show_messages && $messages): ?>
would be checking if (TRUE == TRUE), right?

@yched #16: I understand. Maybe my explanation wasn't clear enough, but that's exactly my point. If <?php if ($show_messages && $messages): ?> is logically equivalent to <?php if ($messages): ?>, then why would the patch solve the problem?

OK I found it. The key to understanding the messages in the installation process is in theme.maintenance.inc, function theme_install_page(), around line 133:

  // Delay setting the message variable so it can be processed below.
  $variables['show_messages'] = FALSE;
  // Variable processors invoked manually since this function and theme_update_page()
  // are exceptions in how it works within the theme system.
  template_preprocess($variables, 'install_page');
  template_preprocess_maintenance_page($variables);
  template_process($variables, 'install_page');

  // Special handling of error messages
  $messages = drupal_set_message();

That means that the messages for the install pages are not processed in template_preprocess_maintenance_page() at all, but in theme_install_page().

I think we can be sure that $show_messages is always processed correctly before the tpl.php is processed, so $show_messages should never be checked in a page template. I'm attaching a new patch which corrects this in both Seven and Garland. (Fingers crossed, I think this patch will pass! :-))

One more patch; in garland/page.tpl.php, print $messages doesn't need to be wrapped in an if-statement at all.

(just a better title)

Nice, thanks everyone. Now we only have to do #638430: Error in error message not readable so the error message will actually be readable :-)