graphql-python
Cannot subscribe to more than one field
Attempting to subscribe to more than one field will only return the first one in the list. There is some obvious offending code in executor.py: `def subscribe_fields(exe_context, parent_type, source_value, fields): exe_context = SubscriberExecutionContext(exe_context)
def on_error(error):
exe_context.report_error(error)
def map_result(data):
if exe_context.errors:
result = ExecutionResult(data=data, errors=exe_context.errors)
else:
result = ExecutionResult(data=data)
exe_context.reset()
return result
observables = []
# assert len(fields) == 1, "Can only subscribe one element at a time."
for response_name, field_asts in fields.items():
result = subscribe_field(exe_context, parent_type, source_value, field_asts, [response_name])
if result is Undefined:
continue
def catch_error(error):
exe_context.errors.append(error)
return Observable.just(None)
# Map observable results
observable = result.catch_exception(catch_error).map(
lambda data: map_result({response_name: data}))
return observable
observables.append(observable)
return Observable.merge(observables)
`
The line return observable causes a bunch of unreachable code and exits the loop early. However, commenting out that line does not appear to fix the problem - if it is removed, only the last item in the subscription list will return.
To solve this, one would need to dig deep into the subscription code and add tests for subscribing to multiple fields (or improve the existing test_accepts_multiple_subscription_fields_defined_in_schema).
Not sure if it's worthwile since this is legacy code - current development happens in GraphQL core 3. But leaving this open for anybody who is willing to tackle this.
