From 7bfa4dafef00d0fe38c836ff2db652b523163017 Mon Sep 17 00:00:00 2001
From: Hubert Hirtz <hubert@hirtz.pm>
Date: Thu, 26 Nov 2020 15:41:18 +0100
Subject: [PATCH] Advertise all caps, CAP DEL them on registration

... so that the JOIN/history batch takes into account all capabilities.
Without this commit for example, enabling multi-prefix after the batch
makes the client send NAMES requests for all channels, which generate
needless traffic.
---
 downstream.go | 9 +++++++++
 user.go       | 2 --
 2 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/downstream.go b/downstream.go
index 2f809ec..3ee0cf7 100644
--- a/downstream.go
+++ b/downstream.go
@@ -555,6 +555,14 @@ func (dc *downstreamConn) handleCapCommand(cmd string, args []string) error {
 				return err
 			}
 		}
+		if !dc.registered && dc.capVersion >= 302 {
+			// Let downstream show everything it supports, and trim
+			// down the available capabilities when upstreams are
+			// known.
+			for k, v := range needAllDownstreamCaps {
+				dc.supportedCaps[k] = v
+			}
+		}
 
 		caps := make([]string, 0, len(dc.supportedCaps))
 		for k, v := range dc.supportedCaps {
@@ -896,6 +904,7 @@ func (dc *downstreamConn) welcome() error {
 	})
 
 	dc.updateNick()
+	dc.updateSupportedCaps()
 
 	dc.forEachUpstream(func(uc *upstreamConn) {
 		for _, ch := range uc.channels {
diff --git a/user.go b/user.go
index 6d54ffc..4118ea5 100644
--- a/user.go
+++ b/user.go
@@ -435,8 +435,6 @@ func (u *user) run() {
 			u.forEachUpstream(func(uc *upstreamConn) {
 				uc.updateAway()
 			})
-
-			dc.updateSupportedCaps()
 		case eventDownstreamDisconnected:
 			dc := e.dc