From 5e051ddb208c21a84fdb01194782da03fd6ebf6c Mon Sep 17 00:00:00 2001
From: Goffi <goffi@goffi.org>
Date: Sat, 20 Jul 2019 20:55:17 +0200
Subject: [PATCH] plugin XEP-0198: catch and log an error if buffer is
 unexpectedly empty

---
 sat/plugins/plugin_xep_0198.py | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/sat/plugins/plugin_xep_0198.py b/sat/plugins/plugin_xep_0198.py
index aabff0b7..77133090 100644
--- a/sat/plugins/plugin_xep_0198.py
+++ b/sat/plugins/plugin_xep_0198.py
@@ -245,8 +245,17 @@ class XEP_0198(object):
         """Update buffer and buffer_index"""
         if server_acked > session.buffer_idx:
             diff = server_acked - session.buffer_idx
-            for i in xrange(diff):
-                session.buffer.pop()
+            try:
+                for i in xrange(diff):
+                    session.buffer.pop()
+            except IndexError:
+                log.error(
+                    u"error while cleaning buffer, invalid index (buffer is empty):\n"
+                    u"diff = {diff}\n"
+                    u"server_acked = {server_acked}\n"
+                    u"buffer_idx = {buffer_id}".format(
+                        diff=diff, server_acked=server_acked,
+                        buffer_id=session.buffer_idx))
             session.buffer_idx += diff
 
     def replayBuffer(self, client, buffer_, discard_results=False):