feat: implement hex display for Bytes (#624)

* feat: implement hex display for Bytes

* chore: add changelog

* feat: impl Display, same as LowerHex

* fix: prepend 0x for hex display

CHANGELOG.md

@@ -7,6 +7,7 @@
 - Fix `format_units` to return a `String` of representing a decimal point float
   such that the decimal places don't get truncated.
   [597](https://github.com/gakonst/ethers-rs/pull/597)
+- Implement hex display format for `ethers::core::Bytes` [#624](https://github.com/gakonst/ethers-rs/pull/624).
 
 ### Unreleased
 

ethers-core/src/types/bytes.rs

@@ -3,6 +3,8 @@ use serde::{
     Deserialize, Deserializer, Serialize, Serializer,
 };
 
+use std::fmt::{Display, Formatter, LowerHex, Result as FmtResult};
+
 /// Wrapper type around Bytes to deserialize/serialize "0x" prefixed ethereum hex strings
 #[derive(Clone, Debug, Default, PartialEq, Eq, Hash, Serialize, Deserialize, Ord, PartialOrd)]
 pub struct Bytes(
@@ -10,6 +12,22 @@ pub struct Bytes(
     pub  bytes::Bytes,
 );
 
+fn bytes_to_hex(b: &Bytes) -> String {
+    hex::encode(b.0.as_ref())
+}
+
+impl Display for Bytes {
+    fn fmt(&self, f: &mut Formatter<'_>) -> FmtResult {
+        write!(f, "0x{}", bytes_to_hex(self))
+    }
+}
+
+impl LowerHex for Bytes {
+    fn fmt(&self, f: &mut Formatter<'_>) -> FmtResult {
+        write!(f, "0x{}", bytes_to_hex(self))
+    }
+}
+
 impl Bytes {
     pub fn to_vec(&self) -> Vec<u8> {
         self.as_ref().to_vec()
@@ -67,3 +85,16 @@ where
         Err(Error::invalid_value(Unexpected::Str(&value), &"0x prefix"))
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn hex_formatting() {
+        let b = Bytes::from(vec![1, 35, 69, 103, 137, 171, 205, 239]);
+        let expected = String::from("0x0123456789abcdef");
+        assert_eq!(format!("{:x}", b), expected);
+        assert_eq!(format!("{}", b), expected);
+    }
+}