fix(api): patch some cmdwin/textlock holes

Problem: there are new ways to escape textlock or break the cmdwin in
nvim_win_set_config and nvim_tabpage_set_win.

Solution: fix them. Use win_goto to check it in nvim_tabpage_set_win and use the
try_start/end pattern like with similar functions such as nvim_set_current_win
(which uses the existing msg_list, if set).

Careful not to use `wp->handle` when printing the window ID in the error message
for nvim_tabpage_set_win, as win_goto autocommands may have freed the window.

On a related note, I have a feeling some API functions ought to be checking
curbuf_locked...

1 files changed, 6 insertions, 0 deletions

diff --git a/src/nvim/api/win_config.c b/src/nvim/api/win_config.c
index bb28000719..dab1e4e80b 100644
--- a/src/nvim/api/win_config.c
+++ b/src/nvim/api/win_config.c
@@ -451,6 +451,12 @@ void nvim_win_set_config(Window window, Dict(win_config) *config, Error *err)
     if (!check_split_disallowed_err(win, err)) {
       return;  // error already set
     }
+    // Can't move the cmdwin or its old curwin to a different tabpage.
+    if ((win == cmdwin_win || win == cmdwin_old_curwin) && parent != NULL
+        && win_find_tabpage(parent) != win_tp) {
+      api_set_error(err, kErrorTypeException, "%s", e_cmdwin);
+      return;
+    }
 
     bool to_split_ok = false;
     // If we are moving curwin to another tabpage, switch windows *before* we remove it from the