From 774a32e5fe732a43b229ab25e24dffa36ac29aa4 Mon Sep 17 00:00:00 2001
From: ii14 <ii14@users.noreply.github.com>
Date: Thu, 27 Apr 2023 22:03:17 +0200
Subject: [PATCH] fix(events): null dereference in autocmd functions

---
 src/nvim/autocmd.c                       |  6 ++++--
 test/functional/autocmd/autocmd_spec.lua | 16 ++++++++++++++++
 2 files changed, 20 insertions(+), 2 deletions(-)

diff --git a/src/nvim/autocmd.c b/src/nvim/autocmd.c
index 7a65f11e80..b5109b4b21 100644
--- a/src/nvim/autocmd.c
+++ b/src/nvim/autocmd.c
@@ -300,7 +300,7 @@ void aucmd_del_for_event_and_group(event_T event, int group)
   AutoCmdVec *const acs = &autocmds[(int)event];
   for (size_t i = 0; i < kv_size(*acs); i++) {
     AutoCmd *const ac = &kv_A(*acs, i);
-    if (ac->pat->group == group) {
+    if (ac->pat != NULL && ac->pat->group == group) {
       aucmd_del(ac);
     }
   }
@@ -2027,6 +2027,7 @@ char *getnextac(int c, void *cookie, int indent, bool do_concat)
 
   assert(apc->auidx < kv_size(*acs));
   AutoCmd *const ac = &kv_A(*acs, apc->auidx);
+  assert(ac->pat != NULL);
   bool oneshot = ac->once;
 
   if (p_verbose >= 9) {
@@ -2288,7 +2289,8 @@ bool au_exists(const char *const arg)
     AutoPat *const ap = kv_A(*acs, i).pat;
     // Only use a pattern when it has not been removed.
     // For buffer-local autocommands, path_fnamecmp() works fine.
-    if ((group == AUGROUP_ALL || ap->group == group)
+    if (ap != NULL
+        && (group == AUGROUP_ALL || ap->group == group)
         && (pattern == NULL
             || (buflocal_buf == NULL
                 ? path_fnamecmp(ap->pat, pattern) == 0
diff --git a/test/functional/autocmd/autocmd_spec.lua b/test/functional/autocmd/autocmd_spec.lua
index 82c7f9502f..da8c7b5ee0 100644
--- a/test/functional/autocmd/autocmd_spec.lua
+++ b/test/functional/autocmd/autocmd_spec.lua
@@ -629,4 +629,20 @@ describe('autocmd', function()
     ]]
     eq(1, eval('g:count'))  -- Added autocommands should not be executed
   end)
+
+  it('no crash when clearing a group inside a callback #23355', function()
+    exec_lua [[
+      vim.cmd "autocmd! TabNew"
+      local group = vim.api.nvim_create_augroup('Test', {})
+      local id
+      id = vim.api.nvim_create_autocmd('TabNew', {
+        group = group,
+        callback = function()
+          vim.api.nvim_del_autocmd(id)
+          vim.api.nvim_create_augroup('Test', { clear = true })
+        end,
+      })
+      vim.cmd "tabnew"
+    ]]
+  end)
 end)