Error with master / upcoming v9.0: "generic_data_handle{raw=..type=void*} cannot be converted to data_handle<double>"

[pramodk]

(thanks to @arnaudon for creating the issue in the BBP JIRA system with a reproducer! 🙌 )

Overview of the issue

When switching to NEURON 9 module (e.g. neuron-nightly wheel), I encountered a crash using bluepyopt-based evaluation. The error I see is:

terminate called after throwing an instance of 'std::runtime_error' what(): generic_data_handle{raw=0x5483510 type=void*} cannot be converted to data_handle<double>

I have attached the reproducer including the necessary MOD files. The example is just using a pickled class based on bluepyopt, I can provide more info on what it is inside, but it's a step protocol applied to a cell.

This same example runs to completion with NEURON v8.2.4.

Expected result/behavior

If NEURON v8.2.4 works then NEURON 9 should also work. If the model is incompatible, the error should be better/self-explanatory.

NEURON setup

• Version: neuron-nightly/master vs 8.2.4
• Installation method: pip or from source
• Other details don't matter

Minimal working example - MWE

• Unpack the attached tarball
• and do:

python3 -m venv env
. env/bin/activate
pip install bluepyopt emodel-generalisation
nrnivmodl mods
python repro.py

To reproduce the issue, uninstall neuron v8.x from venv and install neuron-nightly.

Logs

$ python repro.py
...
works: {'bpo_holding_current': -0.0015625, 'SearchHoldingCurrent.soma.v': <bluepyopt.ephys.responses.TimeVoltageResponse object at 0x7ffc54adc110>}
terminate called after throwing an instance of 'std::runtime_error'
  what():  generic_data_handle{raw=0x3473190 type=void*} cannot be converted to data_handle<double>
Traceback (most recent call last):
  File "/gpfs/bbp.cscs.ch/home/kumbhar/Downloads/repro_neuron9_bug/repro.py", line 20, in <module>
    response = emodel_class.run(cell_model, params, sim=sim)
               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/gpfs/bbp.cscs.ch/home/kumbhar/Downloads/repro_neuron9_bug/env/lib/python3.11/site-packages/emodel_generalisation/model/bpopt.py", line 943, in run
    voltage_min = self.get_voltage_base(
                  ^^^^^^^^^^^^^^^^^^^^^^

Reproducer:: repro_neuron9_bug.tgz