Unable to deploy Plutus NFT Minting Policy parametrized by TxOutRef using cardano-cli

Question

UPDATE: I'm making progress. It is apparent the TxOutRef stored on-chain has some extra-structure. For evidence I "printed" the TxOutRef's of the 'utxo' hard-wired in my minting policy and the one stored onchain. For the former/latter I uncommented the first/second comment in

hasUTxO :: Bool
hasUTxO = case txInfoInputs info of
--  [i] -> traceError . decodeUtf8 . getTxId . txOutRefId $ oref
--  [i] -> traceError . decodeUtf8 . getTxId . txOutRefId . txInInfoOutRef $ i
  _   -> traceError "many inputs"

The "printouts", given by the transaction errors returned by cardano-cli were, respectively:

1.

Command failed: transaction build  Error: The following scripts have execution failures:
<ommited stuff>
The machine terminated because of an error, either from a built-in function or from an explicit use of 'error'.
Script debugging logs: Redeemer decoded successfully
Script context decoded successfully
9c087132a325f6483aca8398bab1a56eda1390e762984ba054c25cafd738486c

Command failed: transaction build  Error: The following scripts have execution failures:
<ommited stuff>
The machine terminated because of an error, either from a built-in function or from an explicit use of 'error'.
Caused by: [
  (builtin decodeUtf8)
  (con
    bytestring #9c087132a325f6483aca8398bab1a56eda1390e762984ba054c25cafd738486c
  )
]
Script debugging logs: Redeemer decoded successfully
Script context decoded successfully

It is apparent that in 2. the relevant txOutRefId is buried inside some extra structure. The question now is, how can I extract the txOutRefId from all this structure?

ORIGINAL POST:

This simple minting policy should serve to mint an NFT by consuming a UTxO parametrized by TxOutRef:

{-# INLINABLE mkPolicy #-}
mkPolicy :: TxOutRef -> () -> ScriptContext -> Bool
mkPolicy utxo () ctx = traceIfFalse "UTxO not consumed" hasUTxO
  where
    info :: TxInfo
    info = scriptContextTxInfo ctx

    hasUTxO :: Bool
    hasUTxO = any (\i -> txInInfoOutRef i == utxo) $ txInfoInputs info

(To simplify, we don’t even check that the number of minted tokens is one, since that is a non-issue here.)

I have been unable to deploy a concrete instance of this minting policy using cardano-cli. I now describe my procedure. Hopefully somebody can point out where the mistake is!

The UPLC policy and corresponding currency symbol are obtained with:

policy :: TxOutRef -> MintingPolicy
policy oref = mkMintingPolicyScript $
  $$(PlutusTx.compile [|| mkUntypedMintingPolicy . mkPolicy ||])
  `PlutusTx.applyCode`
  PlutusTx.liftCode oref

curSymbol :: TxOutRef -> CurrencySymbol
curSymbol = Scripts.scriptCurrencySymbol . policy

Meanwhile I have a wallet on Testnet PreProd with one UTxO:

[bash]$ cardano-cli query utxo --address $(cat wallet1.addr) --testnet-magic 1
                           TxHash                                 TxIx        Amount
--------------------------------------------------------------------------------------
9c087132a325f6483aca8398bab1a56eda1390e762984ba054c25cafd738486c     1        9784666930 lovelace + TxOutDatumNone

so I define an instance of my minting policy with:

oref_1 :: TxOutRef
oref_1 = TxOutRef
  { txOutRefId = TxId "9c087132a325f6483aca8398bab1a56eda1390e762984ba054c25cafd738486c"
  , txOutRefIdx = 1
  }

policy_1 :: MintingPolicy
policy_1 = policy oref_1

curSymbol_1 :: CurrencySymbol
curSymbol_1 = curSymbol oref_1

(Note that I have enabled the language extension OverloadedStrings.)

Now I serialize the minting policy and currency symbol, as well as the unit redeemer, with:

Prelude Deploy SimpleMinting> writePolicy "ledger/mint_1.plutus" policy_1
Right ()
Prelude Deploy SimpleMinting> writeCS "ledger/mint_1.hex" curSymbol_1 
Prelude Deploy SimpleMinting> writeUnit "ledger/unit.json"

where the commands writePolicy, writeCS and writeUnit are defined in this Deploy.hs.

Now, also inside directory 'ledger', I wrote the shell script 'mint.sh':

cardano-cli transaction build \
        --babbage-era \
        --testnet-magic 1 \
        --tx-in $(cat oref1.tmp) \
        --tx-in-collateral $(cat oref1.tmp) \
        --tx-out $(cat wallet1.addr)+"2000000 lovelace"+"1 $(cat mint_1.hex).$(cat tokenName.hex)" \
        --change-address $(cat wallet1.addr) \
        --mint "1 $(cat mint_1.hex).$(cat tokenName.hex)" \
        --mint-script-file mint_1.plutus \
        --mint-redeemer-file unit.json \
        --protocol-params-file protocol-params.json \
        --out-file tx.body

('tokenName.hex' was generated with echo -n "FUNKYTOKEN" | xxd -ps > tokenName.hex.)

Let us verify that 'oref1.tmp' stores the correct TxOutRef as queried above with cardano-cli:

[bash]$ cat oref1.tmp ; echo
9c087132a325f6483aca8398bab1a56eda1390e762984ba054c25cafd738486c#1

which is indeed correct. So we try to build the transaction by executing:

[bash]$ ./mint.sh
Command failed: transaction build  Error: The following scripts have execution failures:
the script for policyId 0 (in the order of the PolicyIds) failed with: 
The Plutus script evaluation failed: An error has occurred:  User error:
The machine terminated because of an error, either from a built-in function or from an explicit use of 'error'.
Script debugging logs: Redeemer decoded successfully
Script context decoded successfully
UTxO not consumed
PT5

The "UTxO not consumed" error message implies that my Minting Policy fails to recognize the TxOutRef. I am really puzzled about what am I doing wrong.

For reference, here is the complete haskell code for the plutus minting policy: SimpleMinting.hs.

Answer 1

Ok, I think I have it...

oref_1 = TxOutRef
  { txOutRefId = TxId "9c087132a325f6483aca8398bab1a56eda1390e762984ba054c25cafd738486c"
  , txOutRefIdx = 1
  }

This is not doing what you expect... you must do some conversions, if not its converting your hex string into something else.

You can do like this:

import qualified Data.Maybe as DataMaybe(fromJust)
import qualified Data.Text as DataText
import qualified PlutusTx.Builtins.Class as TxBuiltinsClass
import qualified Prelude as P
import qualified Text.Hex as TextHex

stringToStrictText :: P.String -> DataText.Text
stringToStrictText = DataText.pack

txOutRef = TextHex.decodeHex P.$ stringToStrictText "9c087132a325f6483aca8398bab1a56eda1390e762984ba054c25cafd738486c"
txOutRef' = TxBuiltinsClass.toBuiltin P.$ DataMaybe.fromJust txOutRef

oref_1 = TxOutRef { txOutRefId = TxId txOutRef', txOutRefIdx = 1 }

For using TextHex you must add this in your cabal file:

  build-depends: 
  hex-text

Answer 2

Did you try to have at least two utxos and use one for the mint and one different for collateral?

--tx-in $(cat oref1.tmp)
--tx-in-collateral $(cat oref2.tmp)