Merge #818: Add helpers to convert to DescriptorPublicKey and Descriptor<DefinitePublicKey> data structures

a00c993 Add helpers to convert from PublicKey & XOnlyPublicKey to Descriptor Keys (Philip Robinson)

Pull request description:

  closes #817

  I added the common cases of converting from `Descriptor<PublicKey>` and `Descriptor<XOnlyPublicKey>` to `Descriptor<DefinitePublicKey>`. Not sure if this is considered too specific but it feels like a use case that will be very common.

ACKs for top commit:
  apoelstra:
    ACK a00c993; successfully ran local tests

Tree-SHA512: 151296fbeca3ccb3e7e76138cb0ba874de8250e5139f0eae5e407a16573ed312af2e25d8c5b79d7ca59c8d673bd819087381287d6551a08a64fea51d7ddd9f9e

Author: apoelstra

src/descriptor/key.rs

@@ -8,7 +8,7 @@ use std::error;
 
 use bitcoin::bip32::{self, XKeyIdentifier};
 use bitcoin::hashes::{hash160, ripemd160, sha256, Hash, HashEngine};
-use bitcoin::key::XOnlyPublicKey;
+use bitcoin::key::{PublicKey, XOnlyPublicKey};
 use bitcoin::secp256k1::{Secp256k1, Signing, Verification};
 
 use crate::prelude::*;
@@ -670,6 +670,18 @@ impl FromStr for DescriptorPublicKey {
     }
 }
 
+impl From<XOnlyPublicKey> for DescriptorPublicKey {
+    fn from(key: XOnlyPublicKey) -> Self {
+        DescriptorPublicKey::Single(SinglePub { origin: None, key: SinglePubKey::XOnly(key) })
+    }
+}
+
+impl From<PublicKey> for DescriptorPublicKey {
+    fn from(key: PublicKey) -> Self {
+        DescriptorPublicKey::Single(SinglePub { origin: None, key: SinglePubKey::FullKey(key) })
+    }
+}
+
 /// Descriptor key conversion error
 #[derive(Debug, PartialEq, Eq, PartialOrd, Ord, Hash, Clone, Copy)]
 pub enum ConversionError {
@@ -1260,7 +1272,7 @@ impl DefiniteDescriptorKey {
     /// Construct an instance from a descriptor key and a derivation index
     ///
     /// Returns `None` if the key contains a wildcard
-    fn new(key: DescriptorPublicKey) -> Option<Self> {
+    pub fn new(key: DescriptorPublicKey) -> Option<Self> {
         if key.has_wildcard() {
             None
         } else {

src/descriptor/mod.rs

@@ -1051,7 +1051,7 @@ mod tests {
     use bitcoin::hashes::Hash;
     use bitcoin::script::PushBytes;
     use bitcoin::sighash::EcdsaSighashType;
-    use bitcoin::{bip32, PublicKey, Sequence};
+    use bitcoin::{bip32, PublicKey, Sequence, XOnlyPublicKey};
 
     use super::{checksum, *};
     use crate::hex_script;
@@ -2183,4 +2183,58 @@ pk(03f28773c2d975288bc7d1d205c3748651b075fbc6610e58cddeeddf8f19405aa8))";
         )
         .unwrap_err();
     }
+
+    #[test]
+    fn convert_public_key_descriptor_to_definite_key() {
+        let descriptor_str = "wsh(or_d(pk(021d4ea7132d4e1a362ee5efd8d0b59dd4d1fe8906eefa7dd812b05a46b73d829b),pk(0302c8bbbb393f32c843149ce36d56405595aaabab2d0e1f4ca5f9de67dd7419f6)))";
+        let full_pk_descriptor: Descriptor<PublicKey> =
+            Descriptor::from_str(descriptor_str).unwrap();
+
+        struct TranslateFullPk;
+
+        impl Translator<bitcoin::PublicKey> for TranslateFullPk {
+            type TargetPk = DefiniteDescriptorKey;
+            type Error = core::convert::Infallible;
+
+            fn pk(
+                &mut self,
+                pk: &bitcoin::PublicKey,
+            ) -> Result<DefiniteDescriptorKey, Self::Error> {
+                Ok(DefiniteDescriptorKey::new(DescriptorPublicKey::from(*pk))
+                    .expect("DescriptorPublicKey from PublicKey has no wildcards"))
+            }
+
+            translate_hash_clone!(bitcoin::PublicKey, DefiniteDescriptorKey, Self::Error);
+        }
+
+        let converted_descriptor = full_pk_descriptor
+            .translate_pk(&mut TranslateFullPk)
+            .expect("infallible");
+
+        assert_eq!(full_pk_descriptor.to_string(), converted_descriptor.to_string());
+
+        let xonly_descriptor_str = "tr(1d4ea7132d4e1a362ee5efd8d0b59dd4d1fe8906eefa7dd812b05a46b73d829b,pk(02c8bbbb393f32c843149ce36d56405595aaabab2d0e1f4ca5f9de67dd7419f6))";
+        let xonly_pk_descriptor: Descriptor<XOnlyPublicKey> =
+            Descriptor::from_str(xonly_descriptor_str).unwrap();
+
+        struct TranslateXOnlyPk;
+
+        impl Translator<XOnlyPublicKey> for TranslateXOnlyPk {
+            type TargetPk = DefiniteDescriptorKey;
+            type Error = core::convert::Infallible;
+
+            fn pk(&mut self, pk: &XOnlyPublicKey) -> Result<DefiniteDescriptorKey, Self::Error> {
+                Ok(DefiniteDescriptorKey::new(DescriptorPublicKey::from(*pk))
+                    .expect("DescriptorPublicKey from XOnlyPublicKey has no wildcards"))
+            }
+
+            translate_hash_clone!(XOnlyPublicKey, DefiniteDescriptorKey, Self::Error);
+        }
+
+        let xonly_converted_descriptor = xonly_pk_descriptor
+            .translate_pk(&mut TranslateXOnlyPk)
+            .expect("infallible");
+
+        assert_eq!(xonly_pk_descriptor.to_string(), xonly_converted_descriptor.to_string());
+    }
 }