vim-patch:8.2.3609: internal error when ModeChanged is triggered recursively

Problem:    Internal error when ModeChanged is triggered when v:event is
            already in use.
Solution:   Save and restore v:event if needed.
3075a45592

In the vim codebase there is no occurrence of get_vim_var_dict(VV_EVENT)
after the above patch, so in order to hold the same invariant in the
neovim codebase we needed to replace more occurrences than the related
vim patch.

src/nvim/aucmd.c

@@ -8,6 +8,7 @@
 #include "nvim/ex_getln.h"
 #include "nvim/fileio.h"
 #include "nvim/main.h"
+#include "nvim/misc1.h"
 #include "nvim/os/os.h"
 #include "nvim/ui.h"
 #include "nvim/vim.h"
@@ -25,13 +26,14 @@ void do_autocmd_uienter(uint64_t chanid, bool attached)
   }
   recursive = true;
 
-  dict_T *dict = get_vim_var_dict(VV_EVENT);
+  save_v_event_T save_v_event;
+  dict_T *dict = get_v_event(&save_v_event);
   assert(chanid < VARNUMBER_MAX);
   tv_dict_add_nr(dict, S_LEN("chan"), (varnumber_T)chanid);
   tv_dict_set_keys_readonly(dict);
   apply_autocmds(attached ? EVENT_UIENTER : EVENT_UILEAVE,
                  NULL, NULL, false, curbuf);
-  tv_dict_clear(dict);
+  restore_v_event(dict, &save_v_event);
 
   recursive = false;
 }

src/nvim/buffer_defs.h

@@ -1116,6 +1116,12 @@ typedef struct {
   pos_T w_cursor_corr;  // corrected cursor position
 } pos_save_T;
 
+// Struct passed to get_v_event() and restore_v_event().
+typedef struct {
+  bool sve_did_save;
+  hashtab_T sve_hashtab;
+} save_v_event_T;
+
 /// Indices into vimmenu_T->strings[] and vimmenu_T->noremap[] for each mode
 /// \addtogroup MENU_INDEX
 /// @{

src/nvim/channel.c

@@ -10,6 +10,7 @@
 #include "nvim/event/socket.h"
 #include "nvim/fileio.h"
 #include "nvim/lua/executor.h"
+#include "nvim/misc1.h"
 #include "nvim/msgpack_rpc/channel.h"
 #include "nvim/msgpack_rpc/server.h"
 #include "nvim/os/shell.h"
@@ -821,7 +822,8 @@ static void set_info_event(void **argv)
   Channel *chan = argv[0];
   event_T event = (event_T)(ptrdiff_t)argv[1];
 
-  dict_T *dict = get_vim_var_dict(VV_EVENT);
+  save_v_event_T save_v_event;
+  dict_T *dict = get_v_event(&save_v_event);
   Dictionary info = channel_info(chan->id);
   typval_T retval;
   (void)object_to_vim(DICTIONARY_OBJ(info), &retval, NULL);
@@ -829,7 +831,7 @@ static void set_info_event(void **argv)
 
   apply_autocmds(event, NULL, NULL, false, curbuf);
 
-  tv_dict_clear(dict);
+  restore_v_event(dict, &save_v_event);
   api_free_dictionary(info);
   channel_decref(chan);
 }

src/nvim/edit.c

@@ -2719,12 +2719,13 @@ static bool pum_enough_matches(void)
 static void trigger_complete_changed_event(int cur)
 {
   static bool recursive = false;
+  save_v_event_T save_v_event;
 
   if (recursive) {
     return;
   }
 
-  dict_T *v_event = get_vim_var_dict(VV_EVENT);
+  dict_T *v_event = get_v_event(&save_v_event);
   if (cur < 0) {
     tv_dict_add_dict(v_event, S_LEN("completed_item"), tv_dict_alloc());
   } else {
@@ -2740,7 +2741,7 @@ static void trigger_complete_changed_event(int cur)
   textlock--;
   recursive = false;
 
-  tv_dict_clear(v_event);
+  restore_v_event(v_event, &save_v_event);
 }
 
 /// Show the popup menu for the list of matches.

src/nvim/ex_getln.c

@@ -880,7 +880,8 @@ static uint8_t *command_line_enter(int firstc, long count, int indent)
   TryState tstate;
   Error err = ERROR_INIT;
   bool tl_ret = true;
-  dict_T *dict = get_vim_var_dict(VV_EVENT);
+  save_v_event_T save_v_event;
+  dict_T *dict = get_v_event(&save_v_event);
   char firstcbuf[2];
   firstcbuf[0] = (char)(firstc > 0 ? firstc : '-');
   firstcbuf[1] = 0;
@@ -894,7 +895,7 @@ static uint8_t *command_line_enter(int firstc, long count, int indent)
 
     apply_autocmds(EVENT_CMDLINEENTER, (char_u *)firstcbuf, (char_u *)firstcbuf,
                    false, curbuf);
-    tv_dict_clear(dict);
+    restore_v_event(dict, &save_v_event);
 
 
     tl_ret = try_leave(&tstate, &err);
@@ -925,7 +926,7 @@ static uint8_t *command_line_enter(int firstc, long count, int indent)
     if (tv_dict_get_number(dict, "abort") != 0) {
       s->gotesc = 1;
     }
-    tv_dict_clear(dict);
+    restore_v_event(dict, &save_v_event);
   }
 
   cmdmsg_rl = false;
@@ -2290,7 +2291,8 @@ static int command_line_changed(CommandLineState *s)
   if (has_event(EVENT_CMDLINECHANGED)) {
     TryState tstate;
     Error err = ERROR_INIT;
-    dict_T *dict = get_vim_var_dict(VV_EVENT);
+    save_v_event_T save_v_event;
+    dict_T *dict = get_v_event(&save_v_event);
 
     char firstcbuf[2];
     firstcbuf[0] = (char)(s->firstc > 0 ? s->firstc : '-');
@@ -2304,7 +2306,7 @@ static int command_line_changed(CommandLineState *s)
 
     apply_autocmds(EVENT_CMDLINECHANGED, (char_u *)firstcbuf,
                    (char_u *)firstcbuf, false, curbuf);
-    tv_dict_clear(dict);
+    restore_v_event(dict, &save_v_event);
 
     bool tl_ret = try_leave(&tstate, &err);
     if (!tl_ret && ERROR_SET(&err)) {

src/nvim/file_search.c

@@ -1603,7 +1603,8 @@ void do_autocmd_dirchanged(char *new_dir, CdScope scope, CdCause cause)
 
   recursive = true;
 
-  dict_T *dict = get_vim_var_dict(VV_EVENT);
+  save_v_event_T save_v_event;
+  dict_T *dict = get_v_event(&save_v_event);
   char buf[8];
 
   switch (scope) {
@@ -1648,7 +1649,7 @@ void do_autocmd_dirchanged(char *new_dir, CdScope scope, CdCause cause)
   apply_autocmds(EVENT_DIRCHANGED, (char_u *)buf, (char_u *)new_dir, false,
                  curbuf);
 
-  tv_dict_clear(dict);
+  restore_v_event(dict, &save_v_event);
 
   recursive = false;
 }

src/nvim/misc1.c

@@ -1060,6 +1060,31 @@ void add_time(char_u *buf, size_t buflen, time_t tt)
   }
 }
 
+dict_T *get_v_event(save_v_event_T *sve)
+{
+  dict_T *v_event = get_vim_var_dict(VV_EVENT);
+
+  if (v_event->dv_hashtab.ht_used > 0) {
+    // recursive use of v:event, save, make empty and restore later
+    sve->sve_did_save = true;
+    sve->sve_hashtab = v_event->dv_hashtab;
+    hash_init(&v_event->dv_hashtab);
+  } else {
+    sve->sve_did_save = false;
+  }
+  return v_event;
+}
+
+void restore_v_event(dict_T *v_event, save_v_event_T *sve)
+{
+  tv_dict_free_contents(v_event);
+  if (sve->sve_did_save) {
+    v_event->dv_hashtab = sve->sve_hashtab;
+  } else {
+    hash_init(&v_event->dv_hashtab);
+  }
+}
+
 /// Fires a ModeChanged autocmd.
 void trigger_modechanged(void)
 {
@@ -1073,7 +1098,8 @@ void trigger_modechanged(void)
     return;
   }
 
-  dict_T *v_event = get_vim_var_dict(VV_EVENT);
+  save_v_event_T save_v_event;
+  dict_T *v_event = get_v_event(&save_v_event);
   tv_dict_add_str(v_event, S_LEN("new_mode"), mode);
   tv_dict_add_str(v_event, S_LEN("old_mode"), last_mode);
 
@@ -1086,6 +1112,5 @@ void trigger_modechanged(void)
   last_mode = mode;
 
   xfree(pat);
-  tv_dict_free_contents(v_event);
-  hash_init(&v_event->dv_hashtab);
+  restore_v_event(v_event, &save_v_event);
 }

src/nvim/ops.c

@@ -2792,8 +2792,9 @@ static void do_autocmd_textyankpost(oparg_T *oap, yankreg_T *reg)
 
   recursive = true;
 
+  save_v_event_T save_v_event;
   // Set the v:event dictionary with information about the yank.
-  dict_T *dict = get_vim_var_dict(VV_EVENT);
+  dict_T *dict = get_v_event(&save_v_event);
 
   // The yanked text contents.
   list_T *const list = tv_list_alloc((ptrdiff_t)reg->y_size);
@@ -2830,7 +2831,7 @@ static void do_autocmd_textyankpost(oparg_T *oap, yankreg_T *reg)
   textlock++;
   apply_autocmds(EVENT_TEXTYANKPOST, NULL, NULL, false, curbuf);
   textlock--;
-  tv_dict_clear(dict);
+  restore_v_event(dict, &save_v_event);
 
   recursive = false;
 }

src/nvim/terminal.c

@@ -324,10 +324,11 @@ void terminal_close(Terminal *term, int status)
   }
 
   if (buf && !is_autocmd_blocked()) {
-    dict_T *dict = get_vim_var_dict(VV_EVENT);
+    save_v_event_T save_v_event;
+    dict_T *dict = get_v_event(&save_v_event);
     tv_dict_add_nr(dict, S_LEN("status"), status);
     apply_autocmds(EVENT_TERMCLOSE, NULL, NULL, false, buf);
-    tv_dict_clear(dict);
+    restore_v_event(dict, &save_v_event);
   }
 }
 

src/nvim/testdir/test_edit.vim

@@ -1721,4 +1721,10 @@ func Test_mode_changes()
   unlet! g:i_to_any
 endfunc
 
+func Test_recursive_ModeChanged()
+  au! ModeChanged * norm 0u
+  sil! norm 
+  au!
+endfunc
+
 " vim: shiftwidth=2 sts=2 expandtab