From 46011a4e874d47d8ca7f1e0d68fcb685944d45c3 Mon Sep 17 00:00:00 2001
From: Sean Dewar <6256228+seandewar@users.noreply.github.com>
Date: Wed, 16 Jul 2025 10:18:19 +0100
Subject: [PATCH] fix(autocmd): fire TabClosed after freeing tab page

Problem: TabClosed is fired after close_buffer is called (after b_nwindows is
decremented) and after the tab page is removed from the list, but before it's
freed. This causes inconsistencies such as the removed tabpage having a valid
handle and functions like nvim_tabpage_get_number returning nonsense.

Solution: fire it after free_tabpage. Try to maintain the Nvim-specific
behaviour of setting `<amatch>` to the old tab page number, and the
(undocumented) behaviour of setting `<abuf>` to the buffer it was showing
(close_buffer sets w_buffer to NULL if it was freed, so it should be OK pass it
to apply_autocmds_group, similar to before).
---
 src/nvim/window.c                         | 22 +++++++---------
 test/functional/autocmd/tabclose_spec.lua | 32 +++++++++++++++++++++++
 2 files changed, 42 insertions(+), 12 deletions(-)

diff --git a/src/nvim/window.c b/src/nvim/window.c
index 5a87f113da..7b5c1269c9 100644
--- a/src/nvim/window.c
+++ b/src/nvim/window.c
@@ -3045,15 +3045,11 @@ bool win_close_othertab(win_T *win, int free_buf, tabpage_T *tp, bool force)
     goto leave_open;
   }
 
-  bool free_tp = false;
+  int free_tp_idx = 0;
 
   // When closing the last window in a tab page remove the tab page.
   if (tp->tp_firstwin == tp->tp_lastwin) {
-    char prev_idx[NUMBUFLEN];
-    if (has_event(EVENT_TABCLOSED)) {
-      vim_snprintf(prev_idx, NUMBUFLEN, "%i", tabpage_index(tp));
-    }
-
+    free_tp_idx = tabpage_index(tp);
     int h = tabline_height();
 
     if (tp == first_tabpage) {
@@ -3070,23 +3066,25 @@ bool win_close_othertab(win_T *win, int free_buf, tabpage_T *tp, bool force)
       }
       ptp->tp_next = tp->tp_next;
     }
-    free_tp = true;
     redraw_tabline = true;
     if (h != tabline_height()) {
       win_new_screen_rows();
     }
-
-    if (has_event(EVENT_TABCLOSED)) {
-      apply_autocmds(EVENT_TABCLOSED, prev_idx, prev_idx, false, win->w_buffer);
-    }
   }
 
   // Free the memory used for the window.
+  buf_T *buf = win->w_buffer;
   int dir;
   win_free_mem(win, &dir, tp);
 
-  if (free_tp) {
+  if (free_tp_idx > 0) {
     free_tabpage(tp);
+
+    if (has_event(EVENT_TABCLOSED)) {
+      char prev_idx[NUMBUFLEN];
+      vim_snprintf(prev_idx, NUMBUFLEN, "%i", free_tp_idx);
+      apply_autocmds(EVENT_TABCLOSED, prev_idx, prev_idx, false, buf);
+    }
   }
   return true;
 
diff --git a/test/functional/autocmd/tabclose_spec.lua b/test/functional/autocmd/tabclose_spec.lua
index fde72cf4d7..b6651b9c31 100644
--- a/test/functional/autocmd/tabclose_spec.lua
+++ b/test/functional/autocmd/tabclose_spec.lua
@@ -4,6 +4,8 @@ local n = require('test.functional.testnvim')()
 local clear, eq = n.clear, t.eq
 local api = n.api
 local command = n.command
+local eval = n.eval
+local exec = n.exec
 
 describe('TabClosed', function()
   before_each(clear)
@@ -48,6 +50,36 @@ describe('TabClosed', function()
         eq('tabclosed:2:2:2', api.nvim_exec('bdelete Xtestfile2', true))
         eq('Xtestfile1', api.nvim_eval('bufname("")'))
       end)
+
+      it('triggers after tab page is properly freed', function()
+        exec([[
+          let s:tp = nvim_get_current_tabpage()
+          let g:buf = bufnr()
+
+          setlocal bufhidden=wipe
+          tabnew
+          au TabClosed * ++once let g:tp_valid = nvim_tabpage_is_valid(s:tp)
+                             \| let g:abuf = expand('<abuf>')
+
+          call nvim_buf_delete(g:buf, #{force: 1})
+        ]])
+        eq(false, eval('g:tp_valid'))
+        eq(false, eval('nvim_buf_is_valid(g:buf)'))
+        eq('', eval('g:abuf'))
+
+        exec([[
+          tabnew
+          let g:buf = bufnr()
+          let s:win = win_getid()
+
+          tabfirst
+          au TabClosed * ++once let g:abuf = expand('<abuf>')
+
+          call nvim_win_close(s:win, 1)
+        ]])
+        eq(true, eval('nvim_buf_is_valid(g:buf)'))
+        eq(eval('g:buf'), tonumber(eval('g:abuf')))
+      end)
     end)
 
     describe('with NR as <afile>', function()