This commit syncs Prater

beacon_node/beacon_chain/src/builder.rs

@@ -417,6 +417,12 @@ where
         let (_, updated_builder) = self.set_genesis_state(genesis_state)?;
         self = updated_builder;
 
+        // Build the committee caches before storing. The database assumes that states have
+        // committee caches built before storing.
+        weak_subj_state
+            .build_all_committee_caches(&self.spec)
+            .map_err(|e| format!("Error building caches on checkpoint state: {:?}", e))?;
+
         // Write the state and block non-atomically, it doesn't matter if they're forgotten
         // about on a crash restart.
         store

beacon_node/beacon_chain/src/validator_pubkey_cache.rs

@@ -111,12 +111,11 @@ impl<T: BeaconChainTypes> ValidatorPubkeyCache<T> {
         state: &BeaconState<T::EthSpec>,
     ) -> Result<(), BeaconChainError> {
         if state.validators().len() > self.pubkeys.len() {
-            // FIXME(sproul): iter_from would be more efficient than `skip` here
             self.import(
                 state
                     .validators()
-                    .iter()
-                    .skip(self.pubkeys.len())
+                    .iter_from(self.pubkeys.len())
+                    .unwrap() // FIXME(sproul)
                     .map(|v| v.pubkey),
             )
         } else {