chain: impl Display for {block, transaction}::Hash

Also add a Display/FromStr round-trip proptest.

zebra-chain/src/block/hash.rs

@@ -22,6 +22,12 @@ use super::Header;
 #[cfg_attr(test, derive(Arbitrary))]
 pub struct Hash(pub [u8; 32]);
 
+impl fmt::Display for Hash {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.write_str(&hex::encode(&self.0))
+    }
+}
+
 impl fmt::Debug for Hash {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         f.debug_tuple("BlockHeaderHash")

zebra-chain/src/block/tests/prop.rs

@@ -17,6 +17,13 @@ proptest! {
         prop_assert_eq![hash, other_hash];
     }
 
+    #[test]
+    fn block_hash_display_fromstr_roundtrip(hash in any::<Hash>()) {
+        let display = format!("{}", hash);
+        let parsed = display.parse::<Hash>().expect("hash should parse");
+        prop_assert_eq!(hash, parsed);
+    }
+
     #[test]
     fn blockheader_roundtrip(header in any::<Header>()) {
         let bytes = header.zcash_serialize_to_vec()?;

zebra-chain/src/transaction/hash.rs

@@ -27,6 +27,12 @@ impl<'a> From<&'a Transaction> for Hash {
     }
 }
 
+impl fmt::Display for Hash {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.write_str(&hex::encode(&self.0))
+    }
+}
+
 impl fmt::Debug for Hash {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         f.debug_tuple("TransactionHash")

zebra-chain/src/transaction/tests/prop.rs

@@ -14,6 +14,13 @@ proptest! {
         prop_assert_eq![tx, tx2];
     }
 
+    #[test]
+    fn transaction_hash_display_fromstr_roundtrip(hash in any::<Hash>()) {
+        let display = format!("{}", hash);
+        let parsed = display.parse::<Hash>().expect("hash should parse");
+        prop_assert_eq!(hash, parsed);
+    }
+
     #[test]
     fn locktime_roundtrip(locktime in any::<LockTime>()) {
         let mut bytes = Cursor::new(Vec::new());