Duplicate CSS includes for wp_register_style() dependencies that are loaded by wp_admin_css_color()

[archon810]

I think there is a bug in the logic that handles dependencies for styles. Allow me to demonstrate.

I am registering a new style for my admin plugin and I want it to load after certain css files, using the dependency method that wp_register_style() offers. I want my css to load after wp-admin.css and colors-classic.css.

wp_register_style('test_css', "http://test.com/wp-content/my-plugin/css/my-plugin-admin.css", array('wp-admin', 'colors-classic'));
wp_enqueue_style('test_css');

This works just fine and my css indeed loads AFTER the 2 dependencies, except there it is followed by a duplicate

<link rel='stylesheet' href='http://test.com/wp-admin/css/colors-classic.css?ver=20081210' type='text/css' media='all' />

I traced it down to line 41 in wp-admin/admin.php:

wp_admin_css_color('classic', __('Blue'), admin_url("css/colors-classic.css"), array('#073447', '#21759B', '#EAF3FA', '#BBD8E7'));

Apparently wp_admin_css_color() doesn't play well with dependency handling and inserts an extra colors-classic.css anyway, even though it's already been inserted, thus creating a duplicate as well as overriding my styles all over again.

This is what the final output looks like right now:

<link rel='stylesheet' href='http://test.com/wp-admin/wp-admin.css?ver=20081210' type='text/css' media='all' />
<link rel='stylesheet' href='http://test.com/wp-admin/css/colors-classic.css?ver=20081210' type='text/css' media='all' />
<link rel='stylesheet' href='http://test.com/wp-content/my-plugin/css/my-plugin-admin.css?ver=2.7.1' type='text/css' media='all' />
<link rel='stylesheet' href='http://test.com/wp-admin/css/global.css?ver=20081210' type='text/css' media='all' />
<link rel='stylesheet' href='http://test.com/wp-admin/css/colors-classic.css?ver=20081210' type='text/css' media='all' />

[azaozz]

This is because you're using directly colors-classic.css as dependency. Color sylesheets are selectable by the user and are queued with handle 'colors'. There's a function to output the right one depending on the user settings. Try using 'colors' as a dependency.

[archon810]

OK, thank you, that worked.

Is this functionality documented anywhere? It's quite easy to confuse 'colors' with 'colors-classic' because the former is also a valid handle. Perhaps a warning somewhere in the documentation would suffice.