SqliteRecorder crashes when using om.slicer in e.g. a constraint

Question

Summary of Issue

SqliteRecorder crashes when using om.slicer in e.g. a constraint.

Issue Type

• [x ] Bug

Description

Traceback:

Traceback (most recent call last):
  File "test_slicer.py", line 38, in <module>
    p.run_model()
  File "/Users/frza/git/OpenMDAO/openmdao/core/problem.py", line 610, in run_model
    self.final_setup()
  File "/Users/frza/git/OpenMDAO/openmdao/core/problem.py", line 959, in final_setup
    self._setup_recording()
  File "/Users/frza/git/OpenMDAO/openmdao/core/problem.py", line 728, in _setup_recording
    self._rec_mgr.startup(self)
  File "/Users/frza/git/OpenMDAO/openmdao/recorders/recording_manager.py", line 91, in startup
    recorder.startup(recording_requester)
  File "/Users/frza/git/OpenMDAO/openmdao/recorders/sqlite_recorder.py", line 394, in startup
    var_settings_json = json.dumps(var_settings)
  File "/usr/local/Cellar/[email protected]/3.8.5/Frameworks/Python.framework/Versions/3.8/lib/python3.8/json/__init__.py", line 231, in dumps
    return _default_encoder.encode(obj)
  File "/usr/local/Cellar/[email protected]/3.8.5/Frameworks/Python.framework/Versions/3.8/lib/python3.8/json/encoder.py", line 199, in encode
    chunks = self.iterencode(o, _one_shot=True)
  File "/usr/local/Cellar/[email protected]/3.8.5/Frameworks/Python.framework/Versions/3.8/lib/python3.8/json/encoder.py", line 257, in iterencode
    return _iterencode(o, 0)
  File "/usr/local/Cellar/[email protected]/3.8.5/Frameworks/Python.framework/Versions/3.8/lib/python3.8/json/encoder.py", line 179, in default
    raise TypeError(f'Object of type {o.__class__.__name__} '
TypeError: Object of type slice is not JSON serializable

Example

Example taken from openmdao/core/tests/test_group.py

import numpy as np
import openmdao.api as om

from openmdao.api import SqliteRecorder

arr_order_1x1 = np.array([1, 2, 3, 4])

class SlicerComp(om.ExplicitComponent):
    def setup(self):
        self.add_input('x', np.ones(4))
        self.add_output('y', 1.0)

    def compute(self, inputs, outputs):
        outputs['y'] = np.sum(inputs['x'])**2.0


p = om.Problem()

p.model.add_subsystem('indep', om.IndepVarComp('x', arr_order_1x1))
p.model.add_subsystem('C1', SlicerComp())
p.model.connect('indep.x', 'C1.x')
p.model.add_constraint('indep.x', indices=om.slicer[2:])

p.model.add_objective('C1.y')

p.setup()
p.run_model()


precorder = SqliteRecorder('poptimization.sqlite')
p.recording_options['record_desvars'] = True 
p.recording_options['record_constraints'] = True 
p.recording_options['record_objectives'] = True 
p.add_recorder(precorder)


p.setup()
p.run_model()
p.cleanup()

Environment

Operating System: OS X 10.15.5, CentOS

Python environment: Python 3.6.1, 3.8.5

Packages: OpenMDAO master branch