Convert theme_admin_block() to Twig

Extracted from meta, removed reference to template_preprocess_admin_block() in twig docblock because that preprocess doesn't exist.

Assigning to me for review during the Drupal Global Sprint Weekend 2014.

1. +++ b/core/modules/system/templates/admin-block.html.twig
   @@ -0,0 +1,28 @@
   + * - block: An array of information about the block, including:
   + *   - show: A boolean flag indicating if the block should be displayed.
   

   Don't use types in twig docblocks. @see https://drupal.org/node/1823416#datatypes

2. +++ b/core/modules/system/templates/admin-block.html.twig
   @@ -0,0 +1,28 @@
   + *     (description should only be output if content is not available).
   

   Should be a capital D in description.

Fixed the points in #6, but why do we pass 'show' to the template at all? When would the template be useful if 'show' is FALSE?

@longwave because 'show' was in the theme function before conversion. I see you're point though, maybe you could open up a follow-up issue to remove that? Likely they could use '#access' => FALSE or something to prevent the output better. Core doesn't use 'show' other that setting it to TRUE and maybe if you ask @webchick nicely she can grep contrib if there are any use-cases.

Reroll, this does not remove 'show' yet though.

Removed 'show' by not trying to render the block in the first place if it ends up empty.

+++ b/core/modules/system/lib/Drupal/system/Controller/SystemController.php
@@ -137,12 +137,10 @@ public function overview() {
 
           if (!empty($block['content']['#content'])) {
-            $block['show'] = TRUE;
+            // Prepare for sorting as in function _menu_tree_check_access().
+            // The weight is offset so it is always positive, with a uniform 5-digits.
+            $blocks[(50000 + $item['weight']) . ' ' . $item['title'] . ' ' . $item['mlid']] = $block;
           }
-
-          // Prepare for sorting as in function _menu_tree_check_access().
-          // The weight is offset so it is always positive, with a uniform 5-digits.
-          $blocks[(50000 + $item['weight']) . ' ' . $item['title'] . ' ' . $item['mlid']] = $block;
         }

Will this negatively effect sorting of empty content items? Is there a way we can test this?

This change means empty content items don't end up in $blocks at all, and the order of the remaining blocks is the same. I don't see the point in putting a structure in $blocks that is tested for display in the theme function; it seems much simpler to exclude it as soon as we know it's empty.

Here's a markup comparison. All looks good! @longwave, if that get's deamed an API change we may have to revert it... but otherwise I'm glad to see it removed. Going to do a quick profiling with those other two and RTBC this.

#2151105: Convert theme_system_admin_index() to Twig
#2151107: Convert theme_system_compact_link() to Twig

Profile of all 3 patches and confirmed they were all on the page.
#2151107-1: Convert theme_system_compact_link() to Twig
#2151105-7: Convert theme_system_admin_index() to Twig
#2151089-11: Convert theme_admin_block() to Twig

Scenario

• /admin/index as front page.
• Full permissions to all users.

=== 8.x..8.x compared (53195a48b6f09..53195b6957e56):

ct  : 141,571|141,571|0|0.0%
wt  : 699,947|697,654|-2,293|-0.3%
cpu : 694,237|691,839|-2,398|-0.3%
mu  : 32,653,568|32,653,568|0|0.0%
pmu : 32,751,144|32,751,144|0|0.0%

http://www.lionsad.de/xhprof-kit/xhprof/xhprof_html/?run1=53195a48b6f09&...

=== 8.x..2151089-theme_system compared (53195a48b6f09..53195bb0cc668):

ct  : 141,571|143,024|1,453|1.0%
wt  : 699,947|703,391|3,444|0.5%
cpu : 694,237|697,723|3,486|0.5%
mu  : 32,653,568|33,003,928|350,360|1.1%
pmu : 32,751,144|33,095,584|344,440|1.1%

http://www.lionsad.de/xhprof-kit/xhprof/xhprof_html/?run1=53195a48b6f09&...

Profiling and Markup are good. If the API change isn't ok we can just RTBC #10. Just a quick fix needed for the docblock here.

+++ b/core/modules/system/templates/admin-block.html.twig
@@ -0,0 +1,26 @@
+ *   - show: A flag indicating if the block should be displayed.

Remove this docblock variable.

Tagging, anybody can pick this up.

Thanks @longwave! Sorry for the nitpick, let's see if this flies!

1. Markup Compared in #2151089-14: Convert theme_admin_block() to Twig
2. Profiled in #2151089-15: Convert theme_admin_block() to Twig
3. Patch looks good to go!

@Cottser: I made that change already in #11? See the interdiff there for details.

Committed and pushed to 8.x. Thanks!

Incidentally, nice catch on the bogus $show variable.

Minor tag cleanup - please ignore.