Fix serde for block.body.grafitti

eth2/types/src/beacon_block_body.rs

@@ -1,5 +1,5 @@
 use crate::test_utils::TestRandom;
-use crate::utils::graffiti_from_hex_str;
+use crate::utils::{graffiti_from_hex_str, graffiti_to_hex_str};
 use crate::*;
 
 use serde_derive::{Deserialize, Serialize};
@@ -16,7 +16,10 @@ use tree_hash_derive::TreeHash;
 pub struct BeaconBlockBody<T: EthSpec> {
     pub randao_reveal: Signature,
     pub eth1_data: Eth1Data,
-    #[serde(deserialize_with = "graffiti_from_hex_str")]
+    #[serde(
+        serialize_with = "graffiti_to_hex_str",
+        deserialize_with = "graffiti_from_hex_str"
+    )]
     pub graffiti: [u8; 32],
     pub proposer_slashings: VariableList<ProposerSlashing, T::MaxProposerSlashings>,
     pub attester_slashings: VariableList<AttesterSlashing<T>, T::MaxAttesterSlashings>,

eth2/types/src/utils/serde_utils.rs

@@ -46,8 +46,20 @@ where
     Ok(array)
 }
 
-// #[allow(clippy::trivially_copy_pass_by_ref)] // Serde requires the `byte` to be a ref.
+pub fn fork_to_hex_str<S>(bytes: &[u8; FORK_BYTES_LEN], serializer: S) -> Result<S::Ok, S::Error>
-pub fn fork_to_hex_str<S>(bytes: &[u8; 4], serializer: S) -> Result<S::Ok, S::Error>
+where
+    S: Serializer,
+{
+    let mut hex_string: String = "0x".to_string();
+    hex_string.push_str(&hex::encode(&bytes));
+
+    serializer.serialize_str(&hex_string)
+}
+
+pub fn graffiti_to_hex_str<S>(
+    bytes: &[u8; GRAFFITI_BYTES_LEN],
+    serializer: S,
+) -> Result<S::Ok, S::Error>
 where
     S: Serializer,
 {