Error "Missing field: commands" when running trigger

Questions
1

I wrote a trigger with the following rule:

acceptRule : Party -> ACS -> Time -> Map CommandId [Command] -> s -> TriggerA ()
acceptRule party acs t pending s = do
  let proposals = getContracts @IssueProposal acs
  let pcids = map fst proposals
  let cmds = map (\cid -> exerciseCmd cid Accept) pcids
  let pendings = map (\c -> c.contractId) cmds
  emitCommands cmds pendings
  pure ()

When I try to run it I get the following message repeated indefinitely:

Command failed: Missing field: commands, code: 3

What am I doing wrong here?

2

I’m somewhat guessing here but I believe that cmds is probably empty. The ledger API does not accept empty list of commands. If that is the issue you can simply wrap it in when:

when (not (null cmds)) (emitCommands cmds pendings)

Might make sense to modify emitCommands to handle this automatically.

3

Thanks. When I try your suggestion I get a type mismatch:

Couldn't match type ‘CommandId’ with ‘()’
      Expected type: TriggerA ()
        Actual type: TriggerA CommandId

I changed it to:

  when (L.null cmds) do
    emitCommands cmds pendings
    pure ()

Is there a one-liner to do the same?

1 Like
4

Ah good point, you can use the void function to turn this into a one-liner:

when (not $ null cmds) $ void $ emitCommands cmds pendings

Note the not. You seem to have lost that when you changed it.

1 Like
5

Ah, thanks. Yep, missed the not but I’ve now ended up using unless anyway.

1 Like
6

Good point, unless makes more sense here.

1 Like