Allow to retrieve a list of modules defining a certain .info file property

Hm. I guess that requires quite some changes:

1) Add a (first) $type argument to allow to specify 'profile', 'module', or 'theme'. I can't think of a use-case where you'd want more than one $type, so this should be fine.

2) Make it fallback to the filesystem in case the database is not available. (similar to drupal_required_modules()) I already wanted to implement this, but I wasn't able to find a piece of code somewhere that implements this condition already -- i.e. what is the exact condition when we have to fallback to the filesystem? The most obvious seems to be MAINTENANCE_MODE == 'install'. -- Or should we simply go with a try...catch control structure? I.e. try to query, and if that fails, fallback to the filesystem?

3) I also realized that we want to switch the $parents and $value arguments, because it's more natural to invoke by mlbi(array('dependencies'), 'taxonomy').

4) Tests, sure - should be trivial.

5) Due to 1), we probably want to rename the function to drupal_not_sure_how(), perhaps drupal_system_info() or similar. Ideally, it should be self-descriptive and match an existing pattern. The returned result of the function is similar to module_list() and system_get_info(), but contrary to those functions, its purpose is to search/filter/find "extensions" that match a certain criteria. Thus, I called it module_list_by_info(), but that is no longer suitable due to 1). -- Simply rename to drupal_list_by_info()?

Ideally, I'd like to flesh out those points before continuing with coding. Thoughts?

Fixed PHPDoc.

Revised patch that includes using drupal_system_listing as fallback if the database is not available and also uses sytem_list_by_info() for drupal_required_modules(). Also splits the *huge* system_info cache into separate cache entries for each array.

Hm. There were a couple of critical performance considerations for the current cache.

Revamped that to keep the current caching for the regular case, and only support the additional types, too.

Looks ready to fly for me.

The last submitted patch, drupal.system-list-by-info.8.patch, failed testing.

Completely revised patch. Most of the changes actually belong to #887870: Make system_list() return full module records.

What effectively remains here after #887870 landed is the addition of system_list_by_info().

@jacine? @moshe?

Maybe I'm not using this correctly, but I'm not getting any data when I try to test this with Skinr.

Instead of:

I'm just tried this:

Shouldn't that return the same array?

Sorry, I didn't properly update the patch for the new signature of system_get_info(). Fixed that.

Also updated the phpDoc + made $value optional, which is a nice use-case - thanks for providing your example.

Yes, if you pass '', then you are filtering for the value ''. Only NULL is no value.

I actually considered whether it could return $info_value instead of the full $info, but figured that calling code can easily work with both, and there may be use-cases, where you want to get $info for all $type that have a certain $property/$value, but you don't necessarily want to work with $property/$value afterwards, but something else in $info.

phpDoc was outdated.

This issue will be moved back into the D8 queue, after it has been tackled, resolved, and committed to Edge 7.x.