Investigate failing config_data test

[danielballan]

I added an xfail to this test in #772

databroker/databroker/tests/test_broker.py

Lines 706 to 761 in 9959b39

	@pytest.mark.xfail(reason="Possibly broken by predeclare, need investigation")
	def test_config_data(db, RE, hw):
	# simple case: one Event Descriptor, one stream
	RE.subscribe(db.insert)
	from ophyd import Device, sim, Component as C
	class SynWithConfig(Device):
	x = C(sim.Signal, value=0)
	y = C(sim.Signal, value=2)
	z = C(sim.Signal, value=3)
	det = SynWithConfig(name='det')
	det.x.name = 'x'
	det.y.name = 'y'
	det.z.name = 'z'
	det.read_attrs = ['x']
	det.configuration_attrs = ['y', 'z']
	uid, = get_uids(RE(count([det])))
	h = db[uid]
	actual = h.config_data('det')
	expected = {'primary': [{'y': 2, 'z': 3}]}
	assert actual == expected
	# generate two Event Descriptors in the primary stream
	@run_decorator()
	def plan():
	# working around 'yield from' here which breaks py2
	for msg in configure(det, {'z': 3}): # no-op
	yield msg
	for msg in trigger_and_read([det]):
	yield msg
	# changing the config after a read generates a new Event Descriptor
	for msg in configure(det, {'z': 4}):
	yield msg
	for msg in trigger_and_read([det]):
	yield msg
	uid, = get_uids(RE(plan()))
	h = db[uid]
	actual = h.config_data('det')
	expected = {'primary': [{'y': 2, 'z': 3}, {'y': 2, 'z': 4}]}
	assert actual == expected
	# generate two streams, primary and baseline -- one Event Descriptor each
	uid, = get_uids(RE(baseline_wrapper(count([det]), [det])))
	h = db[uid]
	actual = h.config_data('det')
	expected = {'primary': [{'y': 2, 'z': 4}],
	'baseline': [{'y': 2, 'z': 4}]}
	assert actual == expected
	# https://github.com/bluesky/databroker/issues/745
	if hasattr(db, 'v2'):
	db.v2[uid]['primary']['config']['det']['y'][:]
	db.v2[uid]['primary']['config']['det']['z'][:]

This failed around the same time as other tests failed due to the change to bluesky that introduced pre-declaring streams by default. I suspect this may be related to that, but have not closely investigated.