Currently, bundles can only store socket values of Geometry Nodes. However, it
can make sense to store other kinds of data too. Specifically, this patch adds
support for storing arbitrary internal data in a bundle. This is useful when
storing e.g. the physics world when implementing a proper physics solver for
Geometry Nodes (like in #143171).
One can still see that the data exists in Geometry Nodes in the tooltip, but one
can't extract it. Built-in nodes can still read that data.
Storing built-in data in bundles can also be done as an alternative to having a
new "internal data socket" as we talked in a workshop in the past:
https://code.blender.org/2024/11/geometry-nodes-workshop-october-2024/#internal-data-sockets
A bundle still has to be copyable. Internal data is expected to use implicit
sharing. That way copying it just requires increasing the user count of the
data.
Pull Request: https://projects.blender.org/blender/blender/pulls/143472
5f132d3f07