Function ProcessPSBT

src/rpc/rawtransaction.cpp:128–212

Update PSBT with information from the mempool, the UTXO set, the txindex, and the provided descriptors. Optionally, sign the inputs that we can using information from the descriptors.

// Update PSBT with information from the mempool, the UTXO set, the txindex, and the provided descriptors.
// Optionally, sign the inputs that we can using information from the descriptors.
PartiallySignedTransaction ProcessPSBT(const std::string& psbt_string, const std::any& context, const HidingSigningProvider& provider, std::optional<int> sighash_type, bool finalize)
{
    // Unserialize the transactions
    util::Result<PartiallySignedTransaction> psbt_res = DecodeBase64PSBT(psbt_string);
    if (!psbt_res) {
        throw JSONRPCError(RPC_DESERIALIZATION_ERROR, strprintf("TX decode failed %s", util::ErrorString(psbt_res).original));
    }
    PartiallySignedTransaction psbtx = *psbt_res;

    if (g_txindex) g_txindex->BlockUntilSyncedToCurrentChain();
    const NodeContext& node = EnsureAnyNodeContext(context);

    // If we can't find the corresponding full transaction for all of our inputs,
    // this will be used to find just the utxos for the segwit inputs for which
    // the full transaction isn't found
    std::map<COutPoint, Coin> coins;

    // Fetch previous transactions:
    // First, look in the txindex and the mempool
    for (PSBTInput& psbt_input : psbtx.inputs) {
        // The `non_witness_utxo` is the whole previous transaction
        if (psbt_input.non_witness_utxo) continue;

        CTransactionRef tx;

        // Look in the txindex
        if (g_txindex) {
            uint256 block_hash;
            g_txindex->FindTx(psbt_input.prev_txid, block_hash, tx);
        }
        // If we still don't have it look in the mempool
        if (!tx) {
            tx = node.mempool->get(psbt_input.prev_txid);
        }
        if (tx) {
            psbt_input.non_witness_utxo = tx;
        } else {
            coins[psbt_input.GetOutPoint()]; // Create empty map entry keyed by prevout
        }
    }

    // If we still haven't found all of the inputs, look for the missing ones in the utxo set
    if (!coins.empty()) {
        FindCoins(node, coins);
        for (PSBTInput& input : psbtx.inputs) {
            // If there are still missing utxos, add them if they were found in the utxo set
            if (!input.non_witness_utxo) {
                const Coin& coin = coins.at(input.GetOutPoint());
                if (!coin.out.IsNull() && IsSegWitOutput(provider, coin.out.scriptPubKey)) {
                    input.witness_utxo = coin.out;
                }
            }
        }
    }

    std::optional<PrecomputedTransactionData> txdata_res = PrecomputePSBTData(psbtx);
    if (!txdata_res) {
        throw JSONRPCPSBTError(common::PSBTError::INVALID_TX);