Implement a general mechanism to send errors via channels about frequenz-channels-python HOT 1 CLOSED

After trying an implementation for this, we come to realize that it doesn't make a lot of sense.

It is actually weird to call receive() and get an exception that is triggered from the other end and it is not really a problem with receive() itself. When we thought about this feature, we were thinking about the PowerDistributor Responses:

https://github.com/frequenz-floss/frequenz-sdk-python/blob/4ce090ce32f539014101f145e8f97fc67990fa9e/src/frequenz/sdk/power_distribution/utils.py#L45-L69

But the problem with that response is that many response types are condensed into one class. What users should (probably) do instead is having a response class hierarchy or using type unions and have different response types as different Python types. For example:

Response = Union[Success, Ignored, Failure, ...]

Or

classDiagram
  Response <|-- Success
  Response <|-- Error
  Error <|-- OutOfBounds
  Response <|-- Ignored
  Response <|-- Failure

The channel then can have type Response, and when receiving responses, for older Python versions isinstance() can be used. For Python 3.10+ the match statement is the perfect fit for this:

match await receiver.receive():
    case Success:
        # all good
    case (Failure as failure):
        # Use failure
    case Error(error_message=msg):
        print(f"Error received: {msg}")
    ...
    case _:
        # Unknown response!

from frequenz-channels-python.