feat: update signer impl for XOnlyPubkey

Author: chaitika

src/signer.rs

@@ -1,4 +1,5 @@
 use alloc::string::ToString;
+use std::collections::BTreeMap;
 
 use bitcoin::{
     psbt::{GetKey, GetKeyError, KeyRequest},
@@ -24,10 +25,9 @@ impl GetKey for Signer {
         for entry in &self.0 {
             match entry {
                 (_, DescriptorSecretKey::Single(prv)) => {
-                    let pk = prv.key.public_key(secp);
-                    if key_request == KeyRequest::Pubkey(pk) {
-                        return Ok(Some(prv.key));
-                    }
+                    let map: BTreeMap<_, _> =
+                        core::iter::once((prv.key.public_key(secp), prv.key)).collect();
+                    return GetKey::get_key(&map, key_request, secp);
                 }
                 (_, desc_sk) => {
                     for desc_sk in desc_sk.clone().into_single_keys() {
@@ -89,6 +89,26 @@ mod test {
         Ok(())
     }
 
+    #[test]
+    fn get_key_x_only_pubkey() -> anyhow::Result<()> {
+        let secp = Secp256k1::new();
+        let wif = "cU6BxEezV8FnkEPBCaFtc4WNuUKmgFaAu6sJErB154GXgMUjhgWe";
+        let prv = bitcoin::PrivateKey::from_wif(wif)?;
+        let (x_only_pk, _parity) = prv.inner.x_only_public_key(&secp);
+
+        let s = format!("wpkh({wif})");
+        let (_, keymap) = Descriptor::parse_descriptor(&secp, &s).unwrap();
+
+        let signer = Signer(keymap);
+        let req = KeyRequest::XOnlyPubkey(x_only_pk);
+        let res = signer.get_key(req, &secp);
+        assert!(matches!(
+            res,
+            Ok(Some(k)) if k.inner.x_only_public_key(&secp).0 == x_only_pk
+        ));
+        Ok(())
+    }
+
     // Test `Signer` can fulfill a bip32 KeyRequest if we know the key origin
     #[test]
     fn get_key_bip32() -> anyhow::Result<()> {