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?

#623992: Reduce {system} database hits makes this much more easy now.

Fixed PHPDoc.

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.

Feedback/RTBC, anyone?

Looks ready to fly for me.

#8: drupal.system-list-by-info.8.patch queued for re-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().

#887870: Make system_list() return full module records is in.

This is what remains.

@jacine? @moshe?

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.