How to customise exported Drupal Features for a particular site

When a site developer exports configuration to code, all the values stored against that configurable container on the site they export from are saved into code. This container can then be taken to another site and imported exactly as it was exported. It may sometimes be desirable to customise some of the variables within the container for a particular environment later.

We all are awaiting, with eager anticipation, the results of the CMI initiative in Drupal 8, but for now the current best way of exporting site configurable into code is with the Features module. Features exports the configurable either with its own methods or by providing a neat interface for the ctools export mechanisms and it does both things very well.

An example of such a situation occurred recently for us when we wanted to export Apache Solr module search page configurations. When these are exported to code, one of the parameters is the solr environment ID which in our setup was different for each server the code was to be deployed onto. We therefore wanted to change the environment id of the search pages when they were imported.

Fortunately, the Apache Solr Drupal module uses ctools to export its configurables to code. When these are imported, a standard Drupal alter hook is called on the imported data before it is saved, the name of this hook differs depending on the type of data being exported and imported and follows the pattern hook_[default hook]_alter(&$defaults).

The example code hook for our scenario is below. We set the default Apache Solr environment id in a variable in that sites settings.php file.


/**
* Implements hook_apachesolr_search_default_searches_alter().
* When loading the default search pages from the features
* export, modify the default env_id of the core_search
* page to be the current default for this environment
* and not what is in the actual export.
*/
function mymodule_apachesolr_search_default_searchers_alter(&$default_search_pages) {
if (!empty($default_search_pages['core_search'])) {
$default_search_pages['core_search']->env_id = variable_get('apachesolr_default_environment', 'solr');
}
}