From 7e9279c44a3cc1a2af8c332a8b7766c2b2cfbb63 Mon Sep 17 00:00:00 2001
From: Romain Ruetschi <romain@informal.systems>
Date: Thu, 11 Jun 2020 14:39:36 +0200
Subject: [PATCH] Throw an error if there are no witnesses when doing fork
 detection

---
 light-client/src/errors.rs     |  3 +++
 light-client/src/peer_list.rs  |  4 ++--
 light-client/src/supervisor.rs | 14 ++++++--------
 3 files changed, 11 insertions(+), 10 deletions(-)

diff --git a/light-client/src/errors.rs b/light-client/src/errors.rs
index 8f58cb45a..afb2de148 100644
--- a/light-client/src/errors.rs
+++ b/light-client/src/errors.rs
@@ -21,6 +21,9 @@ pub enum ErrorKind {
     #[error("store error")]
     Store,
 
+    #[error("no witnesses")]
+    NoWitnesses,
+
     #[error("no valid peer left")]
     NoValidPeerLeft,
 
diff --git a/light-client/src/peer_list.rs b/light-client/src/peer_list.rs
index ce9081ec7..1c5961fdc 100644
--- a/light-client/src/peer_list.rs
+++ b/light-client/src/peer_list.rs
@@ -35,7 +35,7 @@ impl PeerList {
         self.peers.get_mut(&self.primary)
     }
 
-    pub fn secondaries(&self) -> Vec<&Instance> {
+    pub fn witnesses(&self) -> Vec<&Instance> {
         self.peers
             .keys()
             .filter(|peer_id| peer_id != &&self.primary)
@@ -44,7 +44,7 @@ impl PeerList {
     }
 
     #[pre(peer_id != &self.primary)]
-    pub fn remove_secondary(&mut self, peer_id: &PeerId) {
+    pub fn remove_witness(&mut self, peer_id: &PeerId) {
         self.peers.remove(peer_id);
     }
 
diff --git a/light-client/src/supervisor.rs b/light-client/src/supervisor.rs
index dde0fffe9..6b7c197d1 100644
--- a/light-client/src/supervisor.rs
+++ b/light-client/src/supervisor.rs
@@ -115,7 +115,7 @@ impl Supervisor {
                                         forked.push(block.provider);
                                     }
                                     Fork::Faulty(block, _error) => {
-                                        self.peers.remove_secondary(&block.provider);
+                                        self.peers.remove_witness(&block.provider);
                                         // TODO: Log/record the error
                                     }
                                 }
@@ -156,15 +156,13 @@ impl Supervisor {
         light_block: &LightBlock,
         trusted_state: &LightBlock,
     ) -> Result<Option<Vec<Fork>>, Error> {
-        if self.peers.secondaries().is_empty() {
-            return Ok(None);
+        if self.peers.witnesses().is_empty() {
+            bail!(ErrorKind::NoWitnesses);
         }
 
-        let result = self.fork_detector.detect_forks(
-            light_block,
-            &trusted_state,
-            self.peers.secondaries(),
-        )?;
+        let result =
+            self.fork_detector
+                .detect_forks(light_block, &trusted_state, self.peers.witnesses())?;
 
         match result {
             ForkDetection::Detected(forks) => Ok(Some(forks)),