From 10d7212373f09f4d95a22d4070151440f90dd6f5 Mon Sep 17 00:00:00 2001
From: Alan Shaw <alan.shaw@protocol.ai>
Date: Thu, 6 Feb 2020 09:23:30 +0000
Subject: [PATCH] fix: protocols change event

I was spelunking last night and found that pubsub was constantly having it's `onConnect` handler fired from the multicodec topology.

It was because bitswap was calling `dialProtocol` to connect to a peer. `dialProtocol` makes a `PeerInfo` out of the multiaddr it's given but it has no `protocols` i.e. `[]`. This is passed to `peerStore.update()` where we compare `[]` with an array of populated protocols. Obviously there is no intersection here so `change:protocols` was being emitted, even though no protocols were added or removed.

This logic needs to be improved and tested properly but I just wanted to send a PR to document my findings.
---
 src/peer-store/index.js | 17 +++++++----------
 1 file changed, 7 insertions(+), 10 deletions(-)

diff --git a/src/peer-store/index.js b/src/peer-store/index.js
index 72a76675..3ef2a0c5 100644
--- a/src/peer-store/index.js
+++ b/src/peer-store/index.js
@@ -132,19 +132,16 @@ class PeerStore extends EventEmitter {
         multiaddrs: recorded.multiaddrs.toArray()
       })
     }
-
-    // Update protocols
-    // TODO: better track added and removed protocols
-    const protocolsIntersection = new Set(
-      [...recorded.protocols].filter((p) => peerInfo.protocols.has(p))
-    )
-
-    if (protocolsIntersection.size !== peerInfo.protocols.size ||
-      protocolsIntersection.size !== recorded.protocols.size) {
-      for (const protocol of peerInfo.protocols) {
+    
+    let isProtocolsChanged = false
+    for (const protocol of peerInfo.protocols) {
+      if (!recorded.protocols.has(protocol)) {
+        isProtocolsChanged = true
         recorded.protocols.add(protocol)
       }
+    }
 
+    if (isProtocolsChanged) {
       this.emit('change:protocols', {
         peerInfo: recorded,
         protocols: Array.from(recorded.protocols)