fix(code/core-consensus): Only persist votes in the WAL if they have not yet been seen (#902)

Author: romac

code/crates/core-consensus/src/handle/vote.rs

@@ -77,8 +77,9 @@ where
 
     debug_assert_eq!(consensus_height, vote_height);
 
-    // Only append to WAL and store precommits if we're in the validator set
-    if state.is_validator() {
+    // Only append to WAL and store precommits if we're in the validator set,
+    // and we have not yet seen this vote.
+    if state.is_validator() && !state.driver.votes().has_vote(&signed_vote) {
         // Append the vote to the Write-ahead Log
         perform!(
             co,

code/crates/core-votekeeper/src/keeper.rs

@@ -96,7 +96,7 @@ where
             }
         }
 
-        // Add the vote to the round
+        // Tally this vote
         self.votes.add_vote(&vote, weight);
 
         // Update the weight of the validator
@@ -205,6 +205,13 @@ where
         &self.evidence
     }
 
+    /// Check if we have already seen a vote.
+    pub fn has_vote(&self, vote: &SignedVote<Ctx>) -> bool {
+        self.per_round
+            .get(&vote.round())
+            .is_some_and(|per_round| per_round.received_votes().contains(vote))
+    }
+
     /// Apply a vote with a given weight, potentially triggering an output.
     pub fn apply_vote(
         &mut self,