fix(wallet): fix into_descriptor_key for DescriptorPublicKey

..by including the missing match arm for
`DescriptorPublicKey::MultiXPub` when initializing `networks`.

Test that `into_wallet_descriptor` correctly parses a multipath
descriptor and fails if passed a network that is invalid for the
descriptor.

Note that rust-miniscript doesn't support parsing a multipath
descriptor containing extended private keys.

Author: ValuedMammal

wallet/src/descriptor/mod.rs

@@ -917,4 +917,48 @@ mod test {
         assert_eq!(psbt_input.redeem_script, Some(script.to_p2wsh()));
         assert_eq!(psbt_input.witness_script, Some(script));
     }
+
+    #[test]
+    fn test_into_wallet_descriptor_multi() -> anyhow::Result<()> {
+        // See <https://github.com/bitcoindevkit/bdk_wallet/issues/10>
+        let secp = Secp256k1::new();
+
+        // multipath tpub
+        let descriptor_str = "wpkh([9a6a2580/84'/1'/0']tpubDDnGNapGEY6AZAdQbfRJgMg9fvz8pUBrLwvyvUqEgcUfgzM6zc2eVK4vY9x9L5FJWdX8WumXuLEDV5zDZnTfbn87vLe9XceCFwTu9so9Kks/<0;1>/*)";
+        let (descriptor, _key_map) = descriptor_str
+            .into_wallet_descriptor(&secp, Network::Testnet)
+            .expect("should parse multipath tpub");
+
+        assert!(descriptor.is_multipath());
+
+        // invalid network for descriptor
+        let descriptor_str = "wpkh([9a6a2580/84'/0'/0']xpub6DEzNop46vmxR49zYWFnMwmEfawSNmAMf6dLH5YKDY463twtvw1XD7ihwJRLPRGZJz799VPFzXHpZu6WdhT29WnaeuChS6aZHZPFmqczR5K/<0;1>/*)";
+        let res = descriptor_str.into_wallet_descriptor(&secp, Network::Testnet);
+
+        assert!(matches!(
+            res,
+            Err(DescriptorError::Key(KeyError::InvalidNetwork))
+        ));
+
+        // multipath xpub
+        let descriptor_str = "wpkh([9a6a2580/84'/0'/0']xpub6DEzNop46vmxR49zYWFnMwmEfawSNmAMf6dLH5YKDY463twtvw1XD7ihwJRLPRGZJz799VPFzXHpZu6WdhT29WnaeuChS6aZHZPFmqczR5K/<0;1>/*)";
+        let (descriptor, _key_map) = descriptor_str
+            .into_wallet_descriptor(&secp, Network::Bitcoin)
+            .expect("should parse multipath xpub");
+
+        assert!(descriptor.is_multipath());
+
+        // Miniscript can't make an extended private key with multiple paths into a public key.
+        // ref: <https://docs.rs/miniscript/12.3.2/miniscript/descriptor/enum.DescriptorSecretKey.html#method.to_public>
+        let descriptor_str = "wpkh(tprv8ZgxMBicQKsPdy6LMhUtFHAgpocR8GC6QmwMSFpZs7h6Eziw3SpThFfczTDh5rW2krkqffa11UpX3XkeTTB2FvzZKWXqPY54Y6Rq4AQ5R8L/<0;1>/*)";
+        assert!(matches!(
+            Descriptor::parse_descriptor(&secp, descriptor_str),
+            Err(miniscript::Error::Unexpected(..)),
+        ));
+        let _ = descriptor_str
+            .into_wallet_descriptor(&secp, Network::Testnet)
+            .unwrap_err();
+
+        Ok(())
+    }
 }

wallet/src/keys/mod.rs

@@ -27,7 +27,7 @@ use bitcoin::secp256k1::{self, Secp256k1, Signing};
 use bitcoin::bip32;
 use bitcoin::{key::XOnlyPublicKey, Network, PrivateKey, PublicKey};
 
-use miniscript::descriptor::{Descriptor, DescriptorXKey, Wildcard};
+use miniscript::descriptor::{Descriptor, DescriptorMultiXKey, DescriptorXKey, Wildcard};
 pub use miniscript::descriptor::{
     DescriptorPublicKey, DescriptorSecretKey, KeyMap, SinglePriv, SinglePub, SinglePubKey,
     SortedMultiVec,
@@ -880,10 +880,20 @@ impl<Ctx: ScriptContext> IntoDescriptorKey<Ctx> for DescriptorPublicKey {
     fn into_descriptor_key(self) -> Result<DescriptorKey<Ctx>, KeyError> {
         let networks = match self {
             DescriptorPublicKey::Single(_) => any_network(),
-            DescriptorPublicKey::XPub(DescriptorXKey { xkey, .. }) if xkey.network.is_mainnet() => {
-                mainnet_network()
+            DescriptorPublicKey::XPub(DescriptorXKey { xkey, .. }) => {
+                if xkey.network.is_mainnet() {
+                    mainnet_network()
+                } else {
+                    test_networks()
+                }
+            }
+            DescriptorPublicKey::MultiXPub(DescriptorMultiXKey { xkey, .. }) => {
+                if xkey.network.is_mainnet() {
+                    mainnet_network()
+                } else {
+                    test_networks()
+                }
             }
-            _ => test_networks(),
         };
 
         Ok(DescriptorKey::from_public(self, networks))