fix: level means the peer has our heads

1 files changed, 13 insertions, 6 deletions

diff --git a/src/document/sync.rs b/src/document/sync.rs
index 695f272..6eb791e 100644
--- a/src/document/sync.rs
+++ b/src/document/sync.rs
@@ -389,14 +389,21 @@ impl SyncSession {
                     .iter()
                     .all(|hash| doc.get_change_by_hash(hash).is_some())
             });
-            let Some(before) = before.filter(|before| older && level(&before.their_heads)) else {
+            if !before.is_some_and(|before| older && level(&before.their_heads)) {
                 return false;
-            };
-            self.state.their_heads = before.their_heads;
-            self.state.their_have = before.their_have;
-            self.state.their_need = before.their_need;
-            self.state.shared_heads = heads.to_vec();
+            }
         }
+        // Level: the peer has exactly our heads and needs nothing. Said so outright, not
+        // as the message's view (or the one before it): a view whose heads we lacked
+        // names older ones (`known_last_sync`), by which it would seem to lack what came
+        // since.
+        self.state.their_heads = Some(heads.to_vec());
+        self.state.shared_heads = heads.to_vec();
+        self.state.their_have = Some(vec![sync::Have {
+            last_sync: heads.to_vec(),
+            bloom: sync::BloomFilter::default(),
+        }]);
+        self.state.their_need = Some(Vec::new());
         self.state.last_sent_heads = heads.to_vec();
         self.state.have_responded = true;
         true