From 9c5ade9212d897db590aeb6a2a5340e73ffe44d0 Mon Sep 17 00:00:00 2001
From: zeertzjq <zeertzjq@outlook.com>
Date: Fri, 13 Feb 2026 21:02:40 +0800
Subject: [PATCH] fix: wait() checks condition twice on each interval (#37837)

Problem:  wait() checks condition twice on each interval.
Solution: Don't schedule the due callback. Also fix memory leak when
          Nvim exits while waiting.

No test that the condition isn't checked twice, as testing for that can
be flaky when there are libuv events from other sources.
---
 src/nvim/eval/funcs.c                   | 11 +++++++++--
 src/nvim/lua/executor.c                 | 20 ++++++++++++--------
 test/functional/lua/vim_spec.lua        |  9 +++++++++
 test/functional/vimscript/wait_spec.lua | 11 +++++++++++
 4 files changed, 41 insertions(+), 10 deletions(-)

diff --git a/src/nvim/eval/funcs.c b/src/nvim/eval/funcs.c
index 9e5a3631fb..4ddea931a1 100644
--- a/src/nvim/eval/funcs.c
+++ b/src/nvim/eval/funcs.c
@@ -2567,6 +2567,12 @@ static void f_gettagstack(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
 /// Dummy timer callback. Used by f_wait().
 static void dummy_timer_due_cb(TimeWatcher *tw, void *data)
 {
+  // If the main loop is closing, the condition won't be checked again.
+  // Close the timer to avoid leaking resources.
+  if (main_loop.closing) {
+    time_watcher_stop(tw);
+    time_watcher_close(tw, dummy_timer_close_cb);
+  }
 }
 
 /// Dummy timer close callback. Used by f_wait().
@@ -2600,8 +2606,9 @@ static void f_wait(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
 
   // Start dummy timer.
   time_watcher_init(&main_loop, tw, NULL);
-  tw->events = main_loop.events;
-  tw->blockable = true;
+  // Don't schedule the due callback, as that'll lead to two different types of events
+  // on each interval, causing the condition to be checked twice.
+  tw->events = NULL;
   time_watcher_start(tw, dummy_timer_due_cb, (uint64_t)interval, (uint64_t)interval);
 
   typval_T argv = TV_INITIAL_VALUE;
diff --git a/src/nvim/lua/executor.c b/src/nvim/lua/executor.c
index b76244cc2d..93a4fa574a 100644
--- a/src/nvim/lua/executor.c
+++ b/src/nvim/lua/executor.c
@@ -423,12 +423,18 @@ static int nlua_schedule(lua_State *const lstate)
   return 2;
 }
 
-// Dummy timer callback. Used by f_wait().
+// Dummy timer callback. Used by vim.wait().
 static void dummy_timer_due_cb(TimeWatcher *tw, void *data)
 {
+  // If the main loop is closing, the condition won't be checked again.
+  // Close the timer to avoid leaking resources.
+  if (main_loop.closing) {
+    time_watcher_stop(tw);
+    time_watcher_close(tw, dummy_timer_close_cb);
+  }
 }
 
-// Dummy timer close callback. Used by f_wait().
+// Dummy timer close callback. Used by vim.wait().
 static void dummy_timer_close_cb(TimeWatcher *tw, void *data)
 {
   xfree(tw);
@@ -512,12 +518,10 @@ static int nlua_wait(lua_State *lstate)
 
   // Start dummy timer.
   time_watcher_init(&main_loop, tw, NULL);
-  tw->events = loop_events;
-  tw->blockable = true;
-  time_watcher_start(tw,
-                     dummy_timer_due_cb,
-                     (uint64_t)interval,
-                     (uint64_t)interval);
+  // Don't schedule the due callback, as that'll lead to two different types of events
+  // on each interval, causing the condition to be checked twice.
+  tw->events = NULL;
+  time_watcher_start(tw, dummy_timer_due_cb, (uint64_t)interval, (uint64_t)interval);
 
   int pcall_status = 0;
   bool callback_result = false;
diff --git a/test/functional/lua/vim_spec.lua b/test/functional/lua/vim_spec.lua
index e31c215817..049398fc74 100644
--- a/test/functional/lua/vim_spec.lua
+++ b/test/functional/lua/vim_spec.lua
@@ -2379,6 +2379,15 @@ stack traceback:
       )
     end)
 
+    it('does not leak when Nvim exits while waiting', function()
+      n.expect_exit(500, exec_lua, function()
+        vim.defer_fn(function()
+          vim.cmd('qall!')
+        end, 10)
+        vim.wait(10000)
+      end)
+    end)
+
     it('plays nice with `not` when fails', function()
       eq(
         true,
diff --git a/test/functional/vimscript/wait_spec.lua b/test/functional/vimscript/wait_spec.lua
index 0932bd3593..3ac7399c52 100644
--- a/test/functional/vimscript/wait_spec.lua
+++ b/test/functional/vimscript/wait_spec.lua
@@ -78,4 +78,15 @@ describe('wait()', function()
     eq('Vim:E475: Invalid value for argument 3', pcall_err(call, 'wait', 0, 1, 0))
     eq('Vim:E475: Invalid value for argument 3', pcall_err(call, 'wait', 0, 1, ''))
   end)
+
+  it('does not leak when Nvim exits while waiting', function()
+    n.expect_exit(
+      500,
+      source,
+      [[
+        call timer_start(10, {-> execute('qall!')})
+        call wait(10000, 0)
+      ]]
+    )
+  end)
 end)