plugin_dir_path() returns unsanitized path on Windows installs

[johnjamesjacoby]

Currently plugin_dir_path() only returns the result of dirname( $file ), which can produce mixed results on local Windows installations.

Attached patch takes pieces from plugin_basename() and plugins_url() to guarantee a working and accurate plugin directory path is returned in all operating systems.

See ​#BB1596 (and associated revisions) for back-story.

Doubt there's a need to fix plugin_dir_path() -- more likely, the issue is this code in search_theme_directories():

$theme_loc = str_replace(WP_CONTENT_DIR, '', $theme_root);

Probably right.

Possibly related: #4541

I believe this issue mainly arises from the fact that some constants on windows environments contain a mixture of \ and / in the paths (which stems from define( 'ABSPATH', dirname(__FILE__) . '/' ); using \), whilst most core functions standardise on / in created paths.. and even some of the API's do a str_replace('\\','/'..

ideally fixing this as low as possible would be better IMHO.

#19200 - Related?

Replying to nacin:

$theme_loc = str_replace(WP_CONTENT_DIR, '', $theme_root);

This is actually dead code. $theme_loc is set up but never used. It will be removed in #20103.