Cannot geocode location to geofield with geocoder during migration

Problem/Motivation

I have a content type with a location field and a geofield field. That geo field's widget is configured to "Geocode from another field" (the location field) using Geocoder. This works fine when editing and saving nodes, the coordinates are retrieved using the set geocoding service.

However, it does not work when migrating nodes using the migrate module, the location is not geocoded.

The address to geocode is extracted from the respective field item in geocoder_widget_parse_locationfield(). It combines the fields name, street, additional, city, province, country and postalcode into a single address string which is then sent to the set geocoding service. Those fields are all set in the field item when saving a node that has been edited e.g. via node edit form.

However, when migrating, the location field item is built by MigrateLocationFieldHandler::prepare() which only returns an array with the lid instead of a fully populated location array. But geocoder_widget_parse_locationfield() cannot create an address string from that and so nothing is geocoded.

Proposed resolution

It works when fixing MigrateLocationFieldHandler::prepare() by merging the actual location data into the returned array with the lid. I attached a patch.

A different solution would be to change geocoder_widget_parse_locationfield() to fetch the location data via location_load_location($field_item['lid']) if only the lid is given. But as other related modules might have the same issues when processing the location data I do favor fixing MigrateLocationFieldHandler::prepare().