Add custom serde deser to block_body.graffiti

eth2/types/src/beacon_block_body.rs

@@ -1,4 +1,4 @@
-use crate::test_utils::TestRandom;
+use crate::test_utils::{graffiti_from_hex_str, TestRandom};
 use crate::*;
 
 use serde_derive::{Deserialize, Serialize};
@@ -24,6 +24,7 @@ use tree_hash_derive::{CachedTreeHash, TreeHash};
 pub struct BeaconBlockBody {
     pub randao_reveal: Signature,
     pub eth1_data: Eth1Data,
+    #[serde(deserialize_with = "graffiti_from_hex_str")]
     pub graffiti: [u8; 32],
     pub proposer_slashings: Vec<ProposerSlashing>,
     pub attester_slashings: Vec<AttesterSlashing>,

eth2/types/src/test_utils/mod.rs

@@ -22,7 +22,7 @@ pub use rand::{
     RngCore,
     {prng::XorShiftRng, SeedableRng},
 };
-pub use serde_utils::{fork_from_hex_str, u8_from_hex_str};
+pub use serde_utils::{fork_from_hex_str, graffiti_from_hex_str, u8_from_hex_str};
 pub use test_random::TestRandom;
 pub use testing_attestation_builder::TestingAttestationBuilder;
 pub use testing_attestation_data_builder::TestingAttestationDataBuilder;

eth2/types/src/test_utils/serde_utils.rs

@@ -2,6 +2,7 @@ use serde::de::Error;
 use serde::{Deserialize, Deserializer};
 
 pub const FORK_BYTES_LEN: usize = 4;
+pub const GRAFFITI_BYTES_LEN: usize = 32;
 
 pub fn u8_from_hex_str<'de, D>(deserializer: D) -> Result<u8, D::Error>
 where
@@ -32,3 +33,24 @@ where
     }
     Ok(array)
 }
+
+pub fn graffiti_from_hex_str<'de, D>(deserializer: D) -> Result<[u8; GRAFFITI_BYTES_LEN], D::Error>
+where
+    D: Deserializer<'de>,
+{
+    let s: String = Deserialize::deserialize(deserializer)?;
+    let mut array = [0 as u8; GRAFFITI_BYTES_LEN];
+    let decoded: Vec<u8> = hex::decode(&s.as_str()[2..]).map_err(D::Error::custom)?;
+
+    if decoded.len() > GRAFFITI_BYTES_LEN {
+        return Err(D::Error::custom("Fork length too long"));
+    }
+
+    for (i, item) in array.iter_mut().enumerate() {
+        if i > decoded.len() {
+            break;
+        }
+        *item = decoded[i];
+    }
+    Ok(array)
+}