Custom currency error: Cannot build the initial state: Tag "toCardanoPolicyId"

Question

I try to set an initial state of the emulator like so:

test :: IO ()
test = runEmulatorTraceIO' def emCfg myTrace
  where
    dist = Map.fromList [ (senderWallet, Ada.lovelaceValueOf 100_000_000)
                        , (receiverWallet, Ada.lovelaceValueOf 100_000_000)
                        ]
  
    emCfg :: EmulatorConfig
    emCfg = EmulatorConfig (Left dist) def

myTrace :: EmulatorTrace ()
myTrace = do
  void $ Emulator.payToWallet (senderWallet) (receiverWallet) $ Ada.lovelaceValueOf 5_000_000
  void $ Emulator.waitNSlots 1

It works perfectly. However when I set a custom currency ff with:

    dist = Map.fromList [ (senderWallet, Ada.lovelaceValueOf 100_000_000
                           <> Value.singleton "ff" "TokenName" 100_000_000)
                        , (receiverWallet, Ada.lovelaceValueOf 100_000_000)
                        ]

The script compiles but after running test I get this error:

*** Exception: Cannot build the initial state: Tag "toCardanoPolicyId" (Tag "1 bytes" DeserialisationError) CallStack (from HasCallStack):
error, called at src/Wallet/Emulator/Stream.hs:171:12 in plutus-contract-1.0.0.0-68585fe6251fbab3f7ee7ae8755133e693587e4f6afa588ae8db3b056e79dcc0:Wallet.Emulator.Stream

This is plutus-apps v.1.0.0. This code works with some other tags.

How do I fix this? Is this a bug?

Answer 1

ff is not a valid PolicyId (aka CurrencySymbol). It must be 28 bytes.

For examples, see this answer on this similar Github issue https://github.com/input-output-hk/plutus-apps/issues/732#issuecomment-1265261105