fix(filetype): avoid recursive FileType autocmds (#22813)

3 files changed, 42 insertions, 36 deletions

diff --git a/src/nvim/api/options.c b/src/nvim/api/options.c
index 31a2fb3b80..baeb3e88fb 100644
--- a/src/nvim/api/options.c
+++ b/src/nvim/api/options.c
@@ -111,15 +111,15 @@ static buf_T *do_ft_buf(char *filetype, aco_save_T *aco, Error *err)
 
   // Set curwin/curbuf to buf and save a few things.
   aucmd_prepbuf(aco, ftbuf);
-  set_option_value("bufhidden", 0L, "hide", OPT_LOCAL);
-  set_option_value("buftype", 0L, "nofile", OPT_LOCAL);
-  set_option_value("swapfile", 0L, NULL, OPT_LOCAL);
-  set_option_value("modeline", 0L, NULL, OPT_LOCAL);  // 'nomodeline'
-
-  ftbuf->b_p_ft = xstrdup(filetype);
 
   TRY_WRAP(err, {
-    apply_autocmds(EVENT_FILETYPE, ftbuf->b_p_ft, ftbuf->b_fname, true, ftbuf);
+    set_option_value("bufhidden", 0L, "hide", OPT_LOCAL);
+    set_option_value("buftype", 0L, "nofile", OPT_LOCAL);
+    set_option_value("swapfile", 0L, NULL, OPT_LOCAL);
+    set_option_value("modeline", 0L, NULL, OPT_LOCAL);  // 'nomodeline'
+
+    ftbuf->b_p_ft = xstrdup(filetype);
+    do_filetype_autocmd(ftbuf, false);
   });
 
   return ftbuf;
diff --git a/src/nvim/autocmd.c b/src/nvim/autocmd.c
index c66ee4286e..b488dd9f8f 100644
--- a/src/nvim/autocmd.c
+++ b/src/nvim/autocmd.c
@@ -2758,3 +2758,32 @@ void do_autocmd_focusgained(bool gained)
 
   recursive = false;
 }
+
+void do_filetype_autocmd(buf_T *buf, bool force)
+{
+  static bool recursive = false;
+
+  if (recursive && !force) {
+    return;  // disallow recursion
+  }
+
+  char **varp = &buf->b_p_ft;
+  int secure_save = secure;
+
+  // Reset the secure flag, since the value of 'filetype' has
+  // been checked to be safe.
+  secure = 0;
+
+  recursive = true;
+  did_filetype = true;
+  // Only pass true for "force" when it is true or
+  // used recursively, to avoid endless recurrence.
+  apply_autocmds(EVENT_FILETYPE, buf->b_p_ft, buf->b_fname, force, buf);
+  recursive = false;
+
+  // Just in case the old "buf" is now invalid
+  if (varp != &(buf->b_p_ft)) {
+    varp = NULL;
+  }
+  secure = secure_save;
+}
diff --git a/src/nvim/optionstr.c b/src/nvim/optionstr.c
index 170800b4e6..bf4ebbb3e2 100644
--- a/src/nvim/optionstr.c
+++ b/src/nvim/optionstr.c
@@ -1529,34 +1529,6 @@ static void do_syntax_autocmd(buf_T *buf, bool value_changed)
   syn_recursive--;
 }
 
-static void do_filetype_autocmd(buf_T *buf, char **varp, int opt_flags, bool value_changed)
-{
-  // 'filetype' is set, trigger the FileType autocommand
-  // Skip this when called from a modeline and the filetype was
-  // already set to this value.
-  if (!(opt_flags & OPT_MODELINE) || value_changed) {
-    static int ft_recursive = 0;
-    int secure_save = secure;
-
-    // Reset the secure flag, since the value of 'filetype' has
-    // been checked to be safe.
-    secure = 0;
-
-    ft_recursive++;
-    did_filetype = true;
-    // Only pass true for "force" when the value changed or not
-    // used recursively, to avoid endless recurrence.
-    apply_autocmds(EVENT_FILETYPE, buf->b_p_ft, buf->b_fname,
-                   value_changed || ft_recursive == 1, buf);
-    ft_recursive--;
-    // Just in case the old "buf" is now invalid
-    if (varp != &(buf->b_p_ft)) {
-      varp = NULL;
-    }
-    secure = secure_save;
-  }
-}
-
 static void do_spelllang_source(win_T *win)
 {
   char fname[200];
@@ -1884,7 +1856,12 @@ static char *did_set_string_option_for(buf_T *buf, win_T *win, int opt_idx, char
     if (varp == &buf->b_p_syn) {
       do_syntax_autocmd(buf, value_changed);
     } else if (varp == &buf->b_p_ft) {
-      do_filetype_autocmd(buf, varp, opt_flags, value_changed);
+      // 'filetype' is set, trigger the FileType autocommand
+      // Skip this when called from a modeline
+      // Force autocmd when the filetype was changed
+      if (!(opt_flags & OPT_MODELINE) || value_changed) {
+        do_filetype_autocmd(buf, value_changed);
+      }
     } else if (varp == &win->w_s->b_p_spl) {
       do_spelllang_source(win);
     }