Deflake async peer registration and harden PeerList.All

sei-tendermint/internal/statesync/dispatcher.go

@@ -283,7 +283,9 @@ func (l *PeerList) Remove(peer types.NodeID) {
 func (l *PeerList) All() []types.NodeID {
 	l.mtx.Lock()
 	defer l.mtx.Unlock()
-	return l.peers
+	peers := make([]types.NodeID, len(l.peers))
+	copy(peers, l.peers)
+	return peers
 }
 
 func (l *PeerList) Contains(id types.NodeID) bool {

sei-tendermint/internal/statesync/dispatcher_test.go

@@ -235,6 +235,23 @@ func TestPeerListBasic(t *testing.T) {
 	assert.Equal(t, half, peerList.Len())
 }
 
+func TestPeerListAllReturnsSnapshot(t *testing.T) {
+	peerList := NewPeerList()
+	peerSet := createPeerSet(2)
+	for _, peer := range peerSet {
+		peerList.Append(peer)
+	}
+
+	peers := peerList.All()
+	require.Len(t, peers, 2)
+
+	// Mutating the returned list must not mutate the internal peer list.
+	peers[0] = peerSet[1]
+	peers = peerList.All()
+	require.Equal(t, peerSet[0], peers[0])
+	require.Equal(t, peerSet[1], peers[1])
+}
+
 func TestPeerListBlocksWhenEmpty(t *testing.T) {
 	t.Cleanup(leaktest.Check(t))
 	peerList := NewPeerList()

sei-tendermint/internal/statesync/reactor_test.go

@@ -141,6 +141,11 @@ func (rts *reactorTestSuite) AddPeer(t *testing.T) *Node {
 		paramsCh:   orPanic(p2p.OpenChannel(testNode.Router, GetParamsChannelDescriptor())),
 	}
 	rts.node.Connect(t.Context(), testNode)
+	// Peer registration in the reactor is asynchronous, so block until this peer
+	// is visible before returning to callers that may assert on peer counts.
+	require.Eventually(t, func() bool {
+		return rts.reactor.peers.Contains(testNode.NodeID)
+	}, 5*time.Second, 50*time.Millisecond)
 	return n
 }