ensureConcluded fails when channel has been progressed to final

[matthiasgeihs]

Location: backend/eth/conclude, contracts/Adjudicator.sol

Problem: When a channel has been force-update on-chain into a final state, the participants will not have fully signed states. Now, when calling ensureConcluded, it will call concludeFinal, which expects a fully-signed state and thus fails.

Idea: If a channel has been force-updated into final, the client should call conclude instead of concludeFinal, because conclude does not require signatures. The client must be able to detect whether a channel is in a final state on-chain. Usually, we indicate that by setting phase = CONCLUDED. Hence, I suggest that we change the contract such that if a state is force-updated to final, we automatically set phase = CONCLUDED.

Update: We can also apply a quick fix that doesn't require a change in the contracts. We can check whether the current on-chain phase is FORCE_EXECUTION. If this is the case, we know that the state resulted from force execution, which means we do not have the all signatures and need to call conclude instead of concludeFinal.

[ggwpez]

How did you detect this? Do you plan on adding a test for this case?
@matthiasgeihs

[matthiasgeihs]

While working on the app-channel example.

It would probably make sense to add a test case, yes.