Merge bitcoindevkit/bdk#1308: feat(esplora): include previous TxOuts for fee calculation

552f11cb5f66a9366dbc05c801fcae043ebe5b82 feat(esplora): include previous `TxOut`s for fee calculation The previous `TxOut` for transactions received from an external wallet are added as floating `TxOut`s to `TxGraph` to allow for fee calculation. (Wei Chen)

Pull request description:

  ### Description

  Partially implements #1265.

  The previous `TxOut` for transactions received from an external wallet are added as floating `TxOut`s to `TxGraph` to allow for fee calculation.

  ### Notes to the reviewers

  Currently only the `esplora` portion of #1265 has been implemented.
  The `electrum` portion will potentially be done in a new PR, as discussed on the 1/30/24 Lib call.

  ### Checklists

  #### To Do:
  * [ ] Implement `electrum` portion of #1265.

  #### All Submissions:

  * [x] I've signed all my commits
  * [x] I followed the [contribution guidelines](https://github.com/bitcoindevkit/bdk/blob/master/CONTRIBUTING.md)
  * [x] I ran `cargo fmt` and `cargo clippy` before committing

  #### New Features:

  * [x] I've added tests for the new feature
  * [x] I've added docs for the new feature

ACKs for top commit:
  evanlinjin:
    re-ACK 552f11cb5f66a9366dbc05c801fcae043ebe5b82
  danielabrozzoni:
    ACK 552f11cb5f66a9366dbc05c801fcae043ebe5b82

Tree-SHA512: 752a24ebd0b9ad7952c1b093ecb251473e346c77b860c1a80c73418130189227405a0f0d7652967cf8c7b89994e8c37df96cd52b52b6daff9cc8c88b5194069a

crates/esplora/src/async_ext.rs

@@ -1,7 +1,7 @@
 use async_trait::async_trait;
 use bdk_chain::collections::btree_map;
 use bdk_chain::{
-    bitcoin::{BlockHash, OutPoint, ScriptBuf, Txid},
+    bitcoin::{BlockHash, OutPoint, ScriptBuf, TxOut, Txid},
     collections::BTreeMap,
     local_chain::{self, CheckPoint},
     BlockId, ConfirmationTimeHeightAnchor, TxGraph,
@@ -204,6 +204,24 @@ impl EsploraAsyncExt for esplora_client::AsyncClient {
                         if let Some(anchor) = anchor_from_status(&tx.status) {
                             let _ = graph.insert_anchor(tx.txid, anchor);
                         }
+
+                        let previous_outputs = tx.vin.iter().filter_map(|vin| {
+                            let prevout = vin.prevout.as_ref()?;
+                            Some((
+                                OutPoint {
+                                    txid: vin.txid,
+                                    vout: vin.vout,
+                                },
+                                TxOut {
+                                    script_pubkey: prevout.scriptpubkey.clone(),
+                                    value: prevout.value,
+                                },
+                            ))
+                        });
+
+                        for (outpoint, txout) in previous_outputs {
+                            let _ = graph.insert_txout(outpoint, txout);
+                        }
                     }
                 }
 

crates/esplora/src/blocking_ext.rs

@@ -3,7 +3,7 @@ use std::thread::JoinHandle;
 use bdk_chain::collections::btree_map;
 use bdk_chain::collections::BTreeMap;
 use bdk_chain::{
-    bitcoin::{BlockHash, OutPoint, ScriptBuf, Txid},
+    bitcoin::{BlockHash, OutPoint, ScriptBuf, TxOut, Txid},
     local_chain::{self, CheckPoint},
     BlockId, ConfirmationTimeHeightAnchor, TxGraph,
 };
@@ -194,6 +194,24 @@ impl EsploraExt for esplora_client::BlockingClient {
                         if let Some(anchor) = anchor_from_status(&tx.status) {
                             let _ = graph.insert_anchor(tx.txid, anchor);
                         }
+
+                        let previous_outputs = tx.vin.iter().filter_map(|vin| {
+                            let prevout = vin.prevout.as_ref()?;
+                            Some((
+                                OutPoint {
+                                    txid: vin.txid,
+                                    vout: vin.vout,
+                                },
+                                TxOut {
+                                    script_pubkey: prevout.scriptpubkey.clone(),
+                                    value: prevout.value,
+                                },
+                            ))
+                        });
+
+                        for (outpoint, txout) in previous_outputs {
+                            let _ = graph.insert_txout(outpoint, txout);
+                        }
                     }
                 }
 

crates/esplora/tests/async_ext.rs

@@ -109,6 +109,28 @@ pub async fn test_update_tx_graph_without_keychain() -> anyhow::Result<()> {
         )
         .await?;
 
+    // Check to see if we have the floating txouts available from our two created transactions'
+    // previous outputs in order to calculate transaction fees.
+    for tx in graph_update.full_txs() {
+        // Retrieve the calculated fee from `TxGraph`, which will panic if we do not have the
+        // floating txouts available from the transactions' previous outputs.
+        let fee = graph_update.calculate_fee(tx.tx).expect("Fee must exist");
+
+        // Retrieve the fee in the transaction data from `bitcoind`.
+        let tx_fee = env
+            .bitcoind
+            .client
+            .get_transaction(&tx.txid, None)
+            .expect("Tx must exist")
+            .fee
+            .expect("Fee must exist")
+            .abs()
+            .to_sat() as u64;
+
+        // Check that the calculated fee matches the fee from the transaction data.
+        assert_eq!(fee, tx_fee);
+    }
+
     let mut graph_update_txids: Vec<Txid> = graph_update.full_txs().map(|tx| tx.txid).collect();
     graph_update_txids.sort();
     let mut expected_txids = vec![txid1, txid2];

crates/esplora/tests/blocking_ext.rs

@@ -136,6 +136,28 @@ pub fn test_update_tx_graph_without_keychain() -> anyhow::Result<()> {
         1,
     )?;
 
+    // Check to see if we have the floating txouts available from our two created transactions'
+    // previous outputs in order to calculate transaction fees.
+    for tx in graph_update.full_txs() {
+        // Retrieve the calculated fee from `TxGraph`, which will panic if we do not have the
+        // floating txouts available from the transactions' previous outputs.
+        let fee = graph_update.calculate_fee(tx.tx).expect("Fee must exist");
+
+        // Retrieve the fee in the transaction data from `bitcoind`.
+        let tx_fee = env
+            .bitcoind
+            .client
+            .get_transaction(&tx.txid, None)
+            .expect("Tx must exist")
+            .fee
+            .expect("Fee must exist")
+            .abs()
+            .to_sat() as u64;
+
+        // Check that the calculated fee matches the fee from the transaction data.
+        assert_eq!(fee, tx_fee);
+    }
+
     let mut graph_update_txids: Vec<Txid> = graph_update.full_txs().map(|tx| tx.txid).collect();
     graph_update_txids.sort();
     let mut expected_txids = vec![txid1, txid2];