fix: return psbt spend utxo errors

bdk-ffi/src/bitcoin.rs

@@ -1507,10 +1507,14 @@ impl Psbt {
     }
 
     /// Returns the spending utxo for this PSBT's input at `input_index`.
-    pub fn spend_utxo(&self, input_index: u64) -> String {
+    pub fn spend_utxo(&self, input_index: u64) -> Result<String, PsbtError> {
         let psbt = self.0.lock().unwrap();
-        let utxo = psbt.spend_utxo(input_index as usize).unwrap();
-        serde_json::to_string(&utxo).unwrap()
+        let utxo = psbt
+            .spend_utxo(input_index as usize)
+            .map_err(PsbtError::from)?;
+        serde_json::to_string(&utxo).map_err(|error| PsbtError::Serialization {
+            error_message: error.to_string(),
+        })
     }
 
     /// The corresponding key-value map for each input in the unsigned transaction.

bdk-ffi/src/error.rs

@@ -12,6 +12,7 @@ use bdk_wallet::bitcoin::hex::DisplayHex;
 use bdk_wallet::bitcoin::psbt::Error as BdkPsbtError;
 use bdk_wallet::bitcoin::psbt::ExtractTxError as BdkExtractTxError;
 use bdk_wallet::bitcoin::psbt::PsbtParseError as BdkPsbtParseError;
+use bdk_wallet::bitcoin::psbt::SignError as BdkPsbtSignError;
 use bdk_wallet::bitcoin::script::PushBytesError;
 use bdk_wallet::chain::local_chain::CannotConnectError as BdkCannotConnectError;
 use bdk_wallet::chain::rusqlite::Error as BdkSqliteError;
@@ -618,6 +619,18 @@ pub enum PsbtError {
     #[error("output index is out of bounds of non witness script output array")]
     PsbtUtxoOutOfBounds,
 
+    #[error("input index is out of bounds")]
+    InputIndexOutOfBounds,
+
+    #[error("missing spend UTXO in PSBT")]
+    MissingSpendUtxo,
+
+    #[error("PSBT serialization error: {error_message}")]
+    Serialization { error_message: String },
+
+    #[error("PSBT spend UTXO error: {error_message}")]
+    SpendUtxo { error_message: String },
+
     #[error("invalid key: {key}")]
     InvalidKey { key: String },
 
@@ -1542,6 +1555,18 @@ impl From<BdkPsbtError> for PsbtError {
     }
 }
 
+impl From<BdkPsbtSignError> for PsbtError {
+    fn from(error: BdkPsbtSignError) -> Self {
+        match error {
+            BdkPsbtSignError::IndexOutOfBounds(_) => PsbtError::InputIndexOutOfBounds,
+            BdkPsbtSignError::MissingSpendUtxo => PsbtError::MissingSpendUtxo,
+            _ => PsbtError::SpendUtxo {
+                error_message: error.to_string(),
+            },
+        }
+    }
+}
+
 impl From<BdkPsbtParseError> for PsbtParseError {
     fn from(error: BdkPsbtParseError) -> Self {
         match error {

bdk-ffi/src/tests/bitcoin.rs

@@ -1,4 +1,5 @@
 use crate::bitcoin::{Address, AddressData, Key, Network, ProprietaryKey, Psbt};
+use crate::error::PsbtError;
 use bdk_electrum::bdk_core::bitcoin::hex::DisplayHex;
 
 #[test]
@@ -360,7 +361,7 @@ fn test_to_address_data() {
 #[test]
 fn test_psbt_spend_utxo() {
     let psbt = sample_psbt();
-    let psbt_utxo = psbt.spend_utxo(0);
+    let psbt_utxo = psbt.spend_utxo(0).unwrap();
 
     assert_eq!(
         psbt_utxo,
@@ -369,6 +370,14 @@ fn test_psbt_spend_utxo() {
     );
 }
 
+#[test]
+fn test_psbt_spend_utxo_invalid_index_returns_error() {
+    let psbt = sample_psbt();
+    let error = psbt.spend_utxo(1).unwrap_err();
+
+    assert!(matches!(error, PsbtError::InputIndexOutOfBounds));
+}
+
 #[test]
 fn test_psbt_input_length() {
     let psbt = sample_psbt2();

bdk-ffi/src/tests/error.rs

@@ -398,6 +398,23 @@ fn test_error_psbt() {
             PsbtError::PsbtUtxoOutOfBounds,
             "output index is out of bounds of non witness script output array",
         ),
+        (
+            PsbtError::InputIndexOutOfBounds,
+            "input index is out of bounds",
+        ),
+        (PsbtError::MissingSpendUtxo, "missing spend UTXO in PSBT"),
+        (
+            PsbtError::Serialization {
+                error_message: "serialization error".to_string(),
+            },
+            "PSBT serialization error: serialization error",
+        ),
+        (
+            PsbtError::SpendUtxo {
+                error_message: "spend error".to_string(),
+            },
+            "PSBT spend UTXO error: spend error",
+        ),
         (
             PsbtError::InvalidKey {
                 key: "key".to_string(),