floatwin: show error if window is closed immediately #11476

Autocmds may close window while it is being entered, then
win_set_minimal_style(wp) operates on an invalid pointer.

We could silently ignore this instead, but it is unlikely to be
intentional, so it is more useful to show an error.

fix #11383

2 files changed, 8 insertions, 3 deletions

diff --git a/src/nvim/api/vim.c b/src/nvim/api/vim.c
index 9adc61b843..e4a9bd64ff 100644
--- a/src/nvim/api/vim.c
+++ b/src/nvim/api/vim.c
@@ -1096,6 +1096,10 @@ Window nvim_open_win(Buffer buffer, Boolean enter, Dictionary config,
   if (enter) {
     win_enter(wp, false);
   }
+  if (!win_valid(wp)) {
+    api_set_error(err, kErrorTypeException, "Window was closed immediately");
+    return 0;
+  }
   if (buffer > 0) {
     nvim_win_set_buf(wp->handle, buffer, err);
   }
diff --git a/src/nvim/window.c b/src/nvim/window.c
index dee36df433..76fc36607c 100644
--- a/src/nvim/window.c
+++ b/src/nvim/window.c
@@ -4372,9 +4372,10 @@ static void win_goto_hor(bool left, long count)
   }
 }
 
-/*
- * Make window "wp" the current window.
- */
+/// Make window `wp` the current window.
+///
+/// @warning Autocmds may close the window immediately, so caller must check
+///          win_valid(wp).
 void win_enter(win_T *wp, bool undo_sync)
 {
   win_enter_ext(wp, undo_sync, false, false, true, true);