Currently when you want to affect the way requests are routed into Drupal, you have two choices; either you hack the core .htaccess or you move all its content into your virtual host. We all know hacking core is bad but code duplication is also irky and we do not want to miss future updates to .htaccess when upgrading.
This dilemma is not an edge case. Just installing robotstxt.module requires this kind of functionality, not to mention if you have moved from another system to Drupal and want to handle old URLs.
So it looks like a choice between plague and cholera. But actually, there is quite an elegant solution to our problem — rewrite inheritance.
Rewrite inheritance
Using rewrite inheritance is not a new concept to Drupal; it is even recommended in the Multisite Install & Configuration guide. However, the way it is applied only lets the vhost inherit configuration from the main server. Our .htaccess will still come in and ruin everything.
Let us have a look at how it currently works.
$ grep Rewrite /etc/apache2/sites-available/rewritetest
RewriteEngine on
RewriteOptions inherit
RewriteRule ^vhost /works [R=301,L]
$ grep Rewrite .htaccess
RewriteEngine on
RewriteRule ^htaccess /works [R=301,L]
$ curl -I http://rewritetest/vhost
HTTP/1.1 404 Not Found
Server: Apache/2.2.22 (Ubuntu)
$ curl -I http://rewritetest/htaccess
HTTP/1.1 301 Moved Permanently
Server: Apache/2.2.22 (Ubuntu)
Location: http://rewritetest/works
The rewrite rules in our vhost is completely disregarded while the .htaccess works just fine. So the recommended RewriteOptions configuration does nothing.
Now let us see how to fix this, by adding the RewriteOptions configuration to the .htaccess to have it inherit our rewrite rules.
$ grep Rewrite .htaccess
RewriteEngine on
RewriteOptions inherit # Play nice, .htaccess!
RewriteRule ^htaccess /works [R=301,L]
$ curl -I http://rewritetest/htaccess
HTTP/1.1 301 Moved Permanently
Server: Apache/2.2.22 (Ubuntu)
Location: http://rewritetest/works
$ curl -I http://rewritetest/vhost
HTTP/1.1 301 Moved Permanently
Server: Apache/2.2.22 (Ubuntu)
Location: http://rewritetest/works
Bam! Both configurations now work perfectly, side by side. This means we can keep the .htaccess pristine while being able to add our custom rewrite rules.
Where is the patch?
So, when can we expect this in Drupal proper? As soon as I am able to convince chx that this is an excellent idea. Feel free to pitch in if you agree!