hook_options_list() defines the list of options used in a field widget. However, the hook does not provide a way for the module defining the field to adjust the list of options depending on the specific instance. It would be useful to supply the instance as context for the hook.
Add an optional parameter
$instance to the hook.
Patch in #1066274-21: hook_options_list should allow to pass the instance of a field adds and documents the hook. Core committer has okayed the addition.
Commit patch once the core codebase is suitably unfrozen.
User interface changes
Minor, backwards-compatible addition only. No existing code will be affected.
Function signature will change from:
hook_options_list($field, $instance = NULL)
Original report by @pcambra
hook_options_list allows to define the options of a widget for of a field, but it only passes $field as parameter to generate the options, so I think it would make sense to include $instance as well, so the instance context is available to the modules that need to define the options listed in a widget form depending on the instance.