Cannot call FundPSBT with a psbt with only a zero value OP_RETURN output

[benthecarman]

When creating trying to fund a psbt that creates an OP_RETURN with 0 value it gives the error wallet couldn't fund PSBT: PSBT packet must contain at least one input or output. If I change the output to be 1 satoshi, it will work.

[guggero]

The error is coming from here: https://github.com/btcsuite/btcwallet/blob/master/wallet/psbt.go#L54
This checks if there is at least one output in the PSBT. Are you sure that your first attempt with 0 sats actually included the TxOut? If yes, could you please paste a sample PSBT?

[benthecarman]

Here is the psbt cHNidP8BACABAAAAAAEAAAAAAAAAAA1qC2hlbGxvIHdvcmxkAAAAAAAA

decoded:

$ bitcoin-cli decodepsbt cHNidP8BACABAAAAAAEAAAAAAAAAAA1qC2hlbGxvIHdvcmxkAAAAAAAA
{
  "tx": {
    "txid": "b42fab8da654e748e6d0817f1eba248110bb3fa6da1c7e56b10f71bd1a9f2acf",
    "hash": "b42fab8da654e748e6d0817f1eba248110bb3fa6da1c7e56b10f71bd1a9f2acf",
    "version": 1,
    "size": 32,
    "vsize": 32,
    "weight": 128,
    "locktime": 0,
    "vin": [
    ],
    "vout": [
      {
        "value": 0.00000000,
        "n": 0,
        "scriptPubKey": {
          "asm": "OP_RETURN 68656c6c6f20776f726c64",
          "hex": "6a0b68656c6c6f20776f726c64",
          "type": "nulldata"
        }
      }
    ]
  },
  "unknown": {
  },
  "inputs": [
  ],
  "outputs": [
    {
    }
  ],
  "fee": 0.00000000
}

[guggero]

Okay, this is probably a bug in the golang PSBT library... It always expects a TX to be in the witness format, but this one doesn't seem to be. Weird that bitcoind doesn't have the same issue. What tool did you create the PSBT with? Bitcoind or another tool?

[benthecarman]

Okay, this is probably a bug in the golang PSBT library... It always expects a TX to be in the witness format, but this one doesn't seem to be. Weird that bitcoind doesn't have the same issue. What tool did you create the PSBT with? Bitcoind or another tool?

I made it in bitcoin-s.

BIP 174 states it shouldn't be in the witness seralization

| Unsigned Transaction
| PSBT_GLOBAL_UNSIGNED_TX = 0x00
| None
| No key data
|
| The transaction in network serialization. The scriptSigs and witnesses for each input must be empty. The transaction must be in the old serialization format (without witnesses).

[guggero]

Oh, thanks for finding that reference, I wasn't aware of that. Then the code in https://github.com/btcsuite/btcd/blob/master/btcutil/psbt/psbt.go#L217 is incorrect. Could you open an issue in btcd with the example PSBT please?

[Roasbeef]

(btcd PR was merged, but lnd needs to be updated)