fix(electrum): Don't ignore multiple coinbase txs

We would previously insert just one coinbase transaction in the database
if we caught multiple in the same sync.
When we sync with electrum, before committing to the database, we remove
from the update conflicting transactions, using the
`make_txs_consistent` function. This function considers two txs to be
conflicting if they spend from the same outpoint - but every coinbase
transaction spends from the same outpoint!
Here we make sure to avoid filtering out coinbase transactions, by
adding a check on the txid just before we do the filtering.

Fixes bitcoindevkit#1051

src/blockchain/script_sync.rs

@@ -9,7 +9,7 @@ use crate::{
     wallet::time::Instant,
     BlockTime, Error, KeychainKind, LocalUtxo, TransactionDetails,
 };
-use bitcoin::{OutPoint, Script, ScriptBuf, Transaction, TxOut, Txid};
+use bitcoin::{hashes::Hash, OutPoint, Script, ScriptBuf, Transaction, TxOut, Txid};
 use log::*;
 use std::collections::{BTreeMap, BTreeSet, HashMap, HashSet, VecDeque};
 
@@ -444,8 +444,14 @@ impl<'a, D: BatchDatabase> State<'a, D> {
 /// Remove conflicting transactions -- tie breaking them by fee.
 fn make_txs_consistent(txs: &[TransactionDetails]) -> Vec<&TransactionDetails> {
     let mut utxo_index: HashMap<OutPoint, &TransactionDetails> = HashMap::default();
+    let mut coinbase_txs = vec![];
     for tx in txs {
         for input in &tx.transaction.as_ref().unwrap().input {
+            if input.previous_output.txid == Txid::all_zeros() {
+                coinbase_txs.push(tx);
+                break;
+            }
+
             utxo_index
                 .entry(input.previous_output)
                 .and_modify(|existing| match (tx.fee, existing.fee) {
@@ -463,5 +469,6 @@ fn make_txs_consistent(txs: &[TransactionDetails]) -> Vec<&TransactionDetails> {
         .collect::<HashMap<_, _>>()
         .into_iter()
         .map(|(_, tx)| tx)
+        .chain(coinbase_txs)
         .collect()
 }