🐛 Coerce workgraph node attributes to JSON-safe values on save - #798

Had a proper look at this, including where the data actually ends up. The approach is right and I'd keep the str() fallback. Two things.

Gate the fallback on clean_value rather than json.dumps. It's the more generous of the two: it turns any non-str iterable into a list, unwraps BaseType, coerces numpy integers. Currently, _ensure_json_safe runs immediately before it, so anything in that gap gets stringified before clean_value ever sees it. Measured through WorkGraph.save() with the value in error-handler kwargs: {1, 2, 3} stored as [1, 2, 3] on main and '{1, 2, 3}' here, numpy.int64(7) as 7 and now '7', orm.Int(3) as 3 and now 'uuid: <uuid> (unstored) value: 3'.

try:
    clean_value(value)
except ValidationError:
    return str(value)
return value

Nothing is given up: everything clean_value genuinely rejects (Enum, datetime, Path, UUID, etc.) fails json.dumps too, so the fallback still catches all of it. Only the value path though, _ensure_json_safe_key should keep its whitelist, since clean_value doesn't look at dict keys at all and a tuple key otherwise reaches the DB and fails there.

from aiida import load_profile, orm
from node_graph.error_handler import normalize_error_handlers
from aiida_workgraph import WorkGraph, task

load_profile()


@task()
def add(x: int = 1, y: int = 2):
    return x + y


def handle(task, **kwargs):  # never runs, only stored
    return 'retrying'


wg = WorkGraph(
    'mwe',
    error_handlers=normalize_error_handlers(
        {'h': {'executor': handle, 'exit_codes': [1], 'kwargs': {'tags': {1, 2, 3}}}}
    ),
)
wg.add_task(add, name='add1')
wg.save()

stored = orm.load_node(wg.process.pk).base.attributes.get('workgraph_error_handlers')
print(repr(stored['h']['kwargs']['tags']))

main                    [1, 2, 3]      <- list
this PR                 '{1, 2, 3}'    <- str
gated on clean_value    [1, 2, 3]      <- list

WorkGraph.save()
  aiida_workgraph/engine/workgraph.py   on_create()
  aiida_workgraph/utils/__init__.py     save_workgraph_data()   <- _ensure_json_safe(wgdata) runs here
  aiida_workgraph/orm/workgraph.py      setter()                <- node.workgraph_data = ...
  aiida/orm/nodes/attributes.py         NodeAttributes.set()
  aiida/storage/psql_dos/orm/nodes.py   SqlaNode.set_attribute()
                                          -> clean_value(value)

Nothing exercises the save_workgraph_data path. Every test calls _ensure_json_safe directly on a hand-built dict, so the helper is covered but its wiring isn't: deleting the call at all three sites there leaves tests/test_utils.py green (13 passed). Going through WorkGraph.save() also shows the trigger isn't quite the one in the description: an Enum default in a task signature raises earlier, in general_serializer during to_engine_inputs(). What does reach the attribute is error-handler kwargs, copied verbatim, at two sites: a graph-level handler lands in workgraph_error_handlers, a task-level one inside workgraph_data under that task's spec. Happy to push the tests for both I have locally.

Thanks @GeigerJ2 — adopted both points.

Gate: thanks, I wasn't aware of clean_value, that's much nicer. Now {1, 2, 3} stored as [1, 2, 3], numpy.int64(7) as 7, orm.Int(3) as 3.

Wiring: added tests through WorkGraph.save() for both sites and verified they fail when the three _ensure_json_safe call sites are removed. (Edge case spotted by Claude: removing only the workgraph_data_short wrap would still pass, since no test puts a non-storable value where only the short-JSON path sees it. Don't think we need to worry about this.)

Adversarial testing also turned up two further holes, both now fixed:

• a non-dict Mapping (e.g. MappingProxyType with a tuple key) skipped the dict branch, passed clean_value, and failed at store() in the database driver — the mapping branch now tests Mapping
• a generator was exhausted by clean_value as a side effect of validation and stored as [] — one-shot iterators are now materialized to lists first

Updated the PR description accordingly.