mce_external_languages/plugins prints twice

[Cyapow]

When adding a language using the 'mce_external_languages' filter the contents get printed for each external plugin loaded.

to fix wp-includes/class.wp-editor.php line 210 add

self::$ext_plugins .= $ext_plugins;

same file line 212 add

$ext_plugins = '';

(first one goes before the foreach loop and the second goes at the beginning of the loop)

Also: #20030 and 20030.diff​

Bug can be replicated for external plugins with:

function trac20030_mce_external_plugins( $plugins ) {
   $plugins['myplugin1'] = WP_PLUGIN_URL . '/myplugin1.js';
   $plugins['myplugin2'] = WP_PLUGIN_URL . '/myplugin2.js';
   return $plugins;
}
add_filter( 'mce_external_plugins', 'trac20030_mce_external_plugins' );

Almost the same as 20030.diff and 19648.patch but keep self::$ext_plugins .= $ext_plugins; in the code block that runs only once per load.

In [19913]:

Stop WP_Editor from outputting TinyMCE external plugins/languages multiple times. Props Cyapow. Fixes #19648.