Add ability to use filters in Extension Customizer

[aaronhuisinga]

Hey Redux team!
I've come across an issue that has been reported before, but a non-BC breaking PR has never been opened. I think this takes care of fixing both my issue, and also not breaking anything for existing Redux users.

The problem:
Users of Bedrock (https://github.com/roots/bedrock) are unable to use the Customizer for themes that take advantage of Redux. This is due to the usage of a non-standard plugins directory location (and I believe a symlink) which causes the required Customizer files (extension_customizer.css and extension_customizer.js) to not load properly, as the _extension_dir and _extension_url variables are incorrect for Bedrock installations.

The solution:
Following the pre-existing pattern of using filters within Redux (I followed the example of the existing redux/_url and redux/_dir filters), I've simply added the ability to define filters to customize these values when necessary. This keeps existing behavior the same for users, and allows developers making use of non-standard WordPress installs to still be able to support Redux in custom configurations without needing to edit the Redux source code.

Related Issues I Referenced:
#2519 and #2754

[kprovance]

Not out of the question. My only concern is the path naming. While this works for the extension in the core, the same filter on premium extensions, housed outside of the core fail. So we'd have to add in the extension name...and since multiple instances of Redux are possible, potentially each with their own premium extensions, the opt_name variable would need to go in as well. Gotta think big picture. I'll play with this later this week and make sure such a naming convention works in all of these scenarios.

[aaronhuisinga]

@kprovance Thanks! Let me know if there are any adjustments you'd like me to make in order to be considered for a merge. I'm happy to help.

[krombox]

@aaronhuisinga thanks for PR. Your solution is what helped me in similar situation. I am not using bedrock, but i am using custom WP and WP_CONTENT_DIR folders to manage dependencies via composer.

@kprovance Does this PR will be on master branch at some point? Thanks

[dahaupt]

@kprovance I just ran into this issue using Bedrock within my local environment using ddev.

It failed to load some resources e.g.
http://mypage.ddev.local/wp/var/www/html/web/app/plugins/redux-framework/ReduxCore/inc/extensions/customizer/extension_customizer.js

The link should instead be
http://mypage.ddev.local/app/plugins/redux-framework/ReduxCore/inc/extensions/customizer/extension_customizer.js

Anything we can do here to help fixing this behavior? Bedrock seems really great for starting WordPress projects.

[kprovance]

Manually added and credited. Final filters are as noted:

$this->_extension_dir = apply_filters( "redux/extension/customizer/dir", trailingslashit( str_replace( '\\', '/', dirname( __FILE__ ) ) ) );
$this->_extension_url = apply_filters( "redux/extension/customizer/url", site_url( str_replace( trailingslashit( str_replace( '\\', '/', ABSPATH ) ), '', $this->_extension_dir ) ) );