Request to make saxonche an optional dependency

[Nush395]

The primary motivation for this is to enable use of imas-python with TORAX.

From what I can see this is used only in the dd_helpers.py script and am wondering if this can be made an optional dep for users who want to use that script. For TORAX we have already built a data dictionary v4 so would not be using the dd_helpers.py script to generate a data dictionary for example and it does not appear straightforward to use saxonche with our internal systems (as the source is not straightforwardly available).

Please let us know what you think.

[maarten-ic]

Hi @Nush395,

From what I can see this is used only in the dd_helpers.py script

This one will be removed with #48. The only usage of saxonche is then to generate mdsplus models (which requires the not publicly available imas-core dependency) in https://github.com/iterorganization/IMAS-Python/blob/develop/imas/backends/imas_core/mdsplus_model.py#L245

I'd be happy to make saxonche an optional dependency. The impact will be minimal after merging #48. We just need to make some adjustments in mdsplus_model.py:

1. Remove the module-level import of saxonche
2. Use a local import of saxonche in the create_model_ids_xml(...) function and raise an error if saxonche is not available: raise RuntimeError("Building mdsplus models requires the 'saxonche' python package. Please install this package (for example with 'pip install saxonche') and try again.")

@olivhoenen what do you think?

[olivhoenen]

@maarten-ic that sounds neat, I would say go for it!

ps: from previous attempts from @Louwrensth imas-core wheel package systematically failed when using MDSplus, so we may deprecate this backend at some point anyway

[Nush395]

Thank you both for the rapid turnaround on this!