Fix for removed validator past boundary (#84)

Problem: A bug was found where validators who are added to the pool
outside of the boundary of the Steward state, then removed before they
begin getting tracked (validators added during cycle N are tracked in
steward state in cycle N+1) were not getting properly removed. This
caused the state machine to get stuck because the invariant used to keep
the state aligned was failing (`num_pool_validators + validators_added -
validators_to_remove == validator_list.len()`)

Resolution: Make sure we're shifting values for steward state fields
that can be relevant past `num_pool_validators` (which is just the
validators_to_remove and validators_for_immediate_removal). We also
don't want to clear those values at `num_pool_validators` because that
might be a relevant value.

keepers/stakenet-keeper/src/entries/crank_steward.rs

@@ -266,7 +266,7 @@ async fn _handle_instant_removal_validators(
 
     while validators_to_remove.count() != 0 {
         let mut validator_index_to_remove = None;
-        for i in 0..num_validators {
+        for i in 0..all_steward_accounts.validator_list_account.validators.len() as u64 {
             if validators_to_remove.get(i as usize).map_err(|e| {
                 JitoTransactionError::Custom(format!(
                     "Error fetching bitmask index for immediate removed validator: {}/{} - {}",

programs/steward/src/instructions/epoch_maintenance.rs

@@ -85,7 +85,7 @@ pub fn handler(
         if let Some(validator_index_to_remove) = validator_index_to_remove {
             state_account
                 .state
-                .remove_validator(validator_index_to_remove)?;
+                .remove_validator(validator_index_to_remove, validators_in_list)?;
         }
     }
 

programs/steward/src/instructions/instant_remove_validator.rs

@@ -88,7 +88,7 @@ pub fn handler(
 
     state_account
         .state
-        .remove_validator(validator_index_to_remove)?;
+        .remove_validator(validator_index_to_remove, validators_in_list)?;
 
     Ok(())
 }

programs/steward/src/state/steward_state.rs

@@ -460,7 +460,7 @@ impl StewardState {
     }
 
     /// Update internal state when a validator is removed from the pool
-    pub fn remove_validator(&mut self, index: usize) -> Result<()> {
+    pub fn remove_validator(&mut self, index: usize, validator_list_len: usize) -> Result<()> {
         let marked_for_regular_removal = self.validators_to_remove.get(index)?;
         let marked_for_immediate_removal = self.validators_for_immediate_removal.get(index)?;
 
@@ -494,6 +494,11 @@ impl StewardState {
             self.instant_unstake
                 .set(i, self.instant_unstake.get(next_i)?)?;
             self.progress.set(i, self.progress.get(next_i)?)?;
+        }
+
+        // For state that can be valid past num_pool_validators, we still need to shift the values
+        for i in index..validator_list_len {
+            let next_i = i.checked_add(1).ok_or(StewardError::ArithmeticError)?;
             self.validators_to_remove
                 .set(i, self.validators_to_remove.get(next_i)?)?;
             self.validators_for_immediate_removal
@@ -538,24 +543,17 @@ impl StewardState {
         }
 
         // Clear values on empty last index
-        self.validator_lamport_balances[num_pool_validators] = 0;
+        self.validator_lamport_balances[num_pool_validators] = LAMPORT_BALANCE_DEFAULT;
         self.scores[num_pool_validators] = 0;
         self.yield_scores[num_pool_validators] = 0;
         self.sorted_score_indices[num_pool_validators] = SORTED_INDEX_DEFAULT;
         self.sorted_yield_score_indices[num_pool_validators] = SORTED_INDEX_DEFAULT;
         self.delegations[num_pool_validators] = Delegation::default();
         self.instant_unstake.set(num_pool_validators, false)?;
         self.progress.set(num_pool_validators, false)?;
-        self.validators_to_remove.set(num_pool_validators, false)?;
+        self.validators_to_remove.set(validator_list_len, false)?;
         self.validators_for_immediate_removal
-            .set(num_pool_validators, false)?;
-
-        if marked_for_regular_removal {
-            self.validators_to_remove.set(num_pool_validators, false)?;
-        } else {
-            self.validators_for_immediate_removal
-                .set(num_pool_validators, false)?;
-        }
+            .set(validator_list_len, false)?;
 
         Ok(())
     }