upload_url_path is always overwritten in function wp_upload_dir

[jimmcq]

I need to have a custom upload_path and upload_url_path so that uploads are served from a separate dedicated server. The problem is that the file URL is always being overwritten by a URL that points to a subdirectory under my main wordpress install.

I tracked down the problem to the following code within the wp_upload_dir function of wp-includes/functions.php:

if ( defined('UPLOADS') && ( WP_CONTENT_DIR . '/uploads' != ABSPATH . $upload_path ) ) {
    $dir = ABSPATH . UPLOADS;
    $url = trailingslashit( $siteurl ) . UPLOADS;
}

Because I have an $upload_path defined this conditional is always trigged and the $url is overwitten when I want it to keep it as get_option( 'upload_url_path' )

xref #12549

I think fixes for #12549 address most of this. For MU setups it is customary to make path customizations via the UPLOADS constant.

I'm not really following how I can define UPLOADS to be a path completely outside of the Wordpress install with $dir = ABSPATH . UPLOADS;

That puts it right back under the Wordpress install.

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Also I don't see how to have the upload_url point to a different server with $url = trailingslashit( $siteurl ) . UPLOADS;

What am I missing here and how can the UPLOADS constant help me around that?