Fix incorrect swap index in bubble-down loop in select_messages_to_republish

src/message_pool/msg_chain.rs

@@ -235,6 +235,18 @@ impl Chains {
         }
     }
 
+    pub(in crate::message_pool) fn bubble_down_after_trim(&mut self, from: usize) {
+        let mut j = from;
+        while j < self.key_vec.len().saturating_sub(1) {
+            #[allow(clippy::indexing_slicing)]
+            if self[j].compare(&self[j + 1]) == Ordering::Less {
+                break;
+            }
+            self.key_vec.swap(j, j + 1);
+            j += 1;
+        }
+    }
+
     pub(in crate::message_pool) fn invalidate(&mut self, mut key: Option<NodeKey>) {
         let mut next_keys = vec![];
 

src/message_pool/msgpool/republish.rs

@@ -4,8 +4,6 @@
 //! Tracks which CIDs were already broadcast in the current republish cycle
 //! and exposes a trigger to wake the republish task early.
 
-use std::cmp::Ordering;
-
 use crate::message::{MessageRead as _, SignedMessage};
 use crate::message_pool::{
     Error,
@@ -174,15 +172,7 @@ where
         // we can't fit the current chain but there is gas to spare
         // trim it and push it down
         chains.trim_msgs_at(i, gas_limit, REPUB_MSG_LIMIT, &base_fee);
-        let mut j = i;
-        while j < chains.len() - 1 {
-            #[allow(clippy::indexing_slicing)]
-            if chains[j].compare(&chains[j + 1]) == Ordering::Less {
-                break;
-            }
-            chains.key_vec.swap(i, i + 1);
-            j += 1;
-        }
+        chains.bubble_down_after_trim(i);
     }
 
     if msgs.len() > REPUB_MSG_LIMIT {
@@ -195,6 +185,31 @@ where
 #[cfg(test)]
 mod tests {
     use super::*;
+    use crate::message_pool::msg_chain::MsgChainNode;
+    use crate::shim::econ::TokenAmount;
+
+    fn chains_from_perfs(perfs: &[f64]) -> Chains {
+        let mut chains = Chains::new();
+        let mut key_vec = Vec::with_capacity(perfs.len());
+        for (i, &p) in perfs.iter().enumerate() {
+            let node = MsgChainNode {
+                gas_perf: p,
+                gas_reward: TokenAmount::from_atto(i as u64 + 1),
+                ..Default::default()
+            };
+            chains.push_with(node, &mut key_vec);
+        }
+        chains.key_vec = key_vec;
+        chains
+    }
+
+    #[test]
+    fn bubble_down_after_trim_restores_compare_order() {
+        let mut chains = chains_from_perfs(&[1.0, 5.0, 3.0, 4.0]);
+        chains.bubble_down_after_trim(1);
+        let perfs: Vec<f64> = (0..chains.len()).map(|i| chains[i].gas_perf).collect();
+        assert_eq!(perfs, vec![1.0, 3.0, 4.0, 5.0]);
+    }
 
     #[test]
     fn was_republished_reflects_replace_with() {