error handling: option 1 (PoC)

[rickwierenga]

we've been thinking about ways of adding error handling. this is one possible approach.

it might be easier to understand and play around with the toy example here: https://gist.github.com/rickwierenga/f53281dfcc4bcb5b3e92a4fa5d15163e. it shows the thought

one downside is that with real PLR (not the toy above), writing real error handlers gets quite involved. see the example in this PR.

Trying it out

Here's a simple reproducible example

# Simple test backend based on LiquidHandlerChatterboxBackend
# that will raise an error for tip spot A1
from pylabrobot.liquid_handling.backends.chatterbox import LiquidHandlerChatterboxBackend
class AnnoyBackend(LiquidHandlerChatterboxBackend):
  async def pick_up_tips(self, ops, use_channels, **backend_kwargs):
    if ops[0].resource.get_identifier() == "A1":
      raise ChannelizedError(
        {0: "A1 is not supported"},
      )
    await super().pick_up_tips(ops, use_channels, **backend_kwargs)

# LH setup
from pylabrobot.liquid_handling import LiquidHandler
from pylabrobot.resources.hamilton import STARDeck
backend = AnnoyBackend()
lh = LiquidHandler(backend=backend, deck=STARDeck())
await lh.setup()

# setting up deck
from pylabrobot.resources import TIP_CAR_480_A00, HTF
tip_car = TIP_CAR_480_A00("tip_car")
tip_car[0] = tip_rack = HTF("tips")
lh.deck.assign_child_resource(tip_car, rails=1)

# setting an error handler on LH and picking up a tip from A1
from pylabrobot.liquid_handling.error_handlers import try_next_tip_spot
with lh.on_fail(ChannelizedError, try_next_tip_spot(iter(tip_rack["B1:H1"]))):
  await lh.pick_up_tips(tip_rack["A1"])

output:

Handling error ChannelizedError(errors={0: 'A1 is not supported'}, ) with: <function try_next_tip_spot.<locals>.handler at 0x106ce91b0>
Retrying with tip spots: [TipSpot(name=tips_tipspot_0_1, location=Coordinate(007.200, 059.300, -83.500), size_x=9.0, size_y=9.0, size_z=0, category=tip_spot)] and use channels: [0]
Picking up tips:
pip#  resource             offset           tip type     max volume (µL)  fitting depth (mm)   tip length (mm)  filter    
  p0: tips_tipspot_0_1     0,0,0            HamiltonTip  1065             8                    95.1             Yes     

[rickwierenga]

https://discuss.pylabrobot.org/t/error-handling-api-design/216