Add committees at slot field

beacon_node/http_api/src/lib.rs

@@ -950,6 +950,7 @@ pub fn serve<T: BeaconChainTypes>(
                             Ok(api_types::AttesterData {
                                 pubkey: pubkey.into(),
                                 validator_index,
+                                committees_at_slot: duty.committees_at_slot,
                                 committee_index: duty.index,
                                 committee_length: duty.committee_len as u64,
                                 validator_committee_index: duty.committee_position as u64,

beacon_node/http_api/tests/tests.rs

@@ -1071,6 +1071,7 @@ impl ApiTester {
                         let expected = AttesterData {
                             pubkey: state.validators[i as usize].pubkey.clone().into(),
                             validator_index: i,
+                            committees_at_slot: duty.committees_at_slot,
                             committee_index: duty.index,
                             committee_length: duty.committee_len as u64,
                             validator_committee_index: duty.committee_position as u64,

common/eth2/src/types.rs

@@ -353,6 +353,8 @@ pub struct AttesterData {
     #[serde(with = "serde_utils::quoted_u64")]
     pub validator_index: u64,
     #[serde(with = "serde_utils::quoted_u64")]
+    pub committees_at_slot: u64,
+    #[serde(with = "serde_utils::quoted_u64")]
     pub committee_index: CommitteeIndex,
     #[serde(with = "serde_utils::quoted_u64")]
     pub committee_length: u64,

consensus/types/src/attestation_duty.rs

@@ -12,4 +12,6 @@ pub struct AttestationDuty {
     pub committee_position: usize,
     /// The total number of attesters in the committee.
     pub committee_len: usize,
+    /// The committee count at `attestation_slot`.
+    pub committees_at_slot: u64,
 }

consensus/types/src/beacon_state/committee_cache.rs

@@ -185,6 +185,7 @@ impl CommitteeCache {
                     index,
                     committee_position,
                     committee_len,
+                    committees_at_slot: self.committees_per_slot(),
                 })
             })
     }