Return an error from NodeEntropy::from_bip39_mnemonic in bindings

The uniffi-exposed `from_bip39_mnemonic` constructor was infallible
and took the `Mnemonic` custom type, which parses the string during
argument lifting. An invalid mnemonic would fail the lift and surface
as an unexpected-error call status. The generated Swift wrapper for an
infallible function wraps the call in `try!`, so passing an invalid
mnemonic (e.g., a user typo during wallet restore) aborts the process
with an uncatchable EXC_BREAKPOINT. Kotlin and Python raise their
generic internal exceptions instead.

Following the `from_seed_bytes` precedent, give the constructor a
uniffi-specific signature that takes the mnemonic as a plain string
and returns `Result<NodeEntropy, EntropyError>`, parsing inside the
function and reporting failures via a new
`EntropyError::InvalidMnemonic` variant. The non-uniffi Rust API is
unchanged.

Author: kaloudis

src/entropy.rs

@@ -19,6 +19,8 @@ use crate::io;
 #[derive(Debug, Clone, PartialEq)]
 #[cfg_attr(feature = "uniffi", derive(uniffi::Error))]
 pub enum EntropyError {
+	/// The given BIP 39 mnemonic is invalid.
+	InvalidMnemonic,
 	/// The given seed bytes are invalid, e.g., have invalid length.
 	InvalidSeedBytes,
 	/// The given seed file is invalid, e.g., has invalid length, or could not be read.
@@ -28,6 +30,7 @@ pub enum EntropyError {
 impl fmt::Display for EntropyError {
 	fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
 		match *self {
+			Self::InvalidMnemonic => write!(f, "Given BIP 39 mnemonic is invalid."),
 			Self::InvalidSeedBytes => write!(f, "Given seed bytes are invalid."),
 			Self::InvalidSeedFile => write!(f, "Given seed file is invalid or could not be read."),
 		}
@@ -45,6 +48,18 @@ impl std::error::Error for EntropyError {}
 pub struct NodeEntropy([u8; WALLET_KEYS_SEED_LEN]);
 
 impl NodeEntropy {
+	/// Configures the [`Node`] instance to source its wallet entropy from a [BIP 39] mnemonic.
+	///
+	/// [BIP 39]: https://github.com/bitcoin/bips/blob/master/bip-0039.mediawiki
+	/// [`Node`]: crate::Node
+	#[cfg(not(feature = "uniffi"))]
+	pub fn from_bip39_mnemonic(mnemonic: Mnemonic, passphrase: Option<String>) -> Self {
+		match passphrase {
+			Some(passphrase) => Self(mnemonic.to_seed(passphrase)),
+			None => Self(mnemonic.to_seed("")),
+		}
+	}
+
 	/// Configures the [`Node`] instance to source its wallet entropy from the given
 	/// [`WALLET_KEYS_SEED_LEN`] seed bytes.
 	///
@@ -63,13 +78,19 @@ impl NodeEntropy {
 impl NodeEntropy {
 	/// Configures the [`Node`] instance to source its wallet entropy from a [BIP 39] mnemonic.
 	///
+	/// Will return an error if the given mnemonic is invalid.
+	///
 	/// [BIP 39]: https://github.com/bitcoin/bips/blob/master/bip-0039.mediawiki
 	/// [`Node`]: crate::Node
-	#[cfg_attr(feature = "uniffi", uniffi::constructor)]
-	pub fn from_bip39_mnemonic(mnemonic: Mnemonic, passphrase: Option<String>) -> Self {
+	#[cfg(feature = "uniffi")]
+	#[uniffi::constructor]
+	pub fn from_bip39_mnemonic(
+		mnemonic: String, passphrase: Option<String>,
+	) -> Result<NodeEntropy, EntropyError> {
+		let mnemonic = Mnemonic::parse(&mnemonic).map_err(|_| EntropyError::InvalidMnemonic)?;
 		match passphrase {
-			Some(passphrase) => Self(mnemonic.to_seed(passphrase)),
-			None => Self(mnemonic.to_seed("")),
+			Some(passphrase) => Ok(Self(mnemonic.to_seed(passphrase))),
+			None => Ok(Self(mnemonic.to_seed(""))),
 		}
 	}
 
@@ -166,6 +187,21 @@ impl WordCount {
 mod tests {
 	use super::*;
 
+	#[cfg(feature = "uniffi")]
+	#[test]
+	fn invalid_mnemonic_returns_error() {
+		// A bad checksum must yield an error rather than an argument-lift panic that
+		// aborts the process in the Swift bindings.
+		let invalid = "abandon abandon abandon abandon abandon abandon abandon abandon abandon abandon abandon abandon";
+		assert_eq!(
+			NodeEntropy::from_bip39_mnemonic(invalid.to_string(), None).err(),
+			Some(EntropyError::InvalidMnemonic)
+		);
+
+		let valid = generate_entropy_mnemonic(None);
+		assert!(NodeEntropy::from_bip39_mnemonic(valid.to_string(), None).is_ok());
+	}
+
 	#[test]
 	fn mnemonic_to_entropy_to_mnemonic() {
 		// Test default (24 words)

tests/common/mod.rs

@@ -591,6 +591,9 @@ impl Default for TestConfig {
 		let store_type = Default::default();
 
 		let mnemonic = generate_entropy_mnemonic(None);
+		#[cfg(feature = "uniffi")]
+		let node_entropy = NodeEntropy::from_bip39_mnemonic(mnemonic.to_string(), None).unwrap();
+		#[cfg(not(feature = "uniffi"))]
 		let node_entropy = NodeEntropy::from_bip39_mnemonic(mnemonic, None);
 		let async_payments_role = None;
 		let wallet_rescan_from_height = None;