From 7c0c318dca3054be6c7bacf5a4b3f5a4e47cc949 Mon Sep 17 00:00:00 2001
From: tv <tv@krebsco.de>
Date: Fri, 6 Nov 2026 19:53:27 +0100
Subject: topology neighbours and optional graph

---
 src/swarm/topology/graph.rs | 17 +++++++++--------
 1 file changed, 9 insertions(+), 8 deletions(-)

(limited to 'src/swarm/topology/graph.rs')

diff --git a/src/swarm/topology/graph.rs b/src/swarm/topology/graph.rs
index 92240e9..d8b2921 100644
--- a/src/swarm/topology/graph.rs
+++ b/src/swarm/topology/graph.rs
@@ -34,8 +34,8 @@ pub(crate) fn schemes(addresses: &[String]) -> BTreeSet<String> {
 /// The neighbours of `local` among `members` (by the transports each is on), on each of
 /// `local_transports`: on each, its neighbours among the members on it
 /// (`neighbours`), all together.
-pub(crate) fn neighbours_across(
-    topology: &dyn Topology,
+pub(crate) fn neighbours_across<T: Topology + ?Sized>(
+    topology: &T,
     members: &BTreeMap<String, BTreeSet<String>>,
     local: &str,
     local_transports: &BTreeSet<String>,
@@ -56,9 +56,10 @@ pub(crate) fn neighbours_across(
 }
 
 /// The neighbours of `local` among `members` (which may or may not contain `local`),
-/// skipping members for which `unreachable` holds.
-pub(crate) fn neighbours(
-    topology: &dyn Topology,
+/// skipping members for which `unreachable` holds; none by a topology without a shared
+/// graph.
+pub(crate) fn neighbours<T: Topology + ?Sized>(
+    topology: &T,
     members: &[String],
     local: &str,
     k: usize,
@@ -69,7 +70,7 @@ pub(crate) fn neighbours(
     all.push(local.to_owned());
     topology
         .graph(&all, k, &|m: &str| m != local && unreachable(m), stable)
-        .remove(local)
+        .and_then(|mut graph| graph.remove(local))
         .unwrap_or_default()
 }
 
@@ -88,8 +89,8 @@ impl Topology for RingAndPairs {
         k: usize,
         unreachable: &dyn Fn(&str) -> bool,
         stable: &dyn Fn(&str) -> bool,
-    ) -> BTreeMap<String, BTreeSet<String>> {
-        graph(members, k, unreachable, stable)
+    ) -> Option<BTreeMap<String, BTreeSet<String>>> {
+        Some(graph(members, k, unreachable, stable))
     }
 }
 
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