feat(api): remove Lua autocommand callbacks when they return true (#17784)

This copies the semantics of nvim_buf_attach callbacks, and is a
convenient way to create oneshot autocommands gated by some condition.

2 files changed, 17 insertions, 6 deletions

diff --git a/src/nvim/autocmd.c b/src/nvim/autocmd.c
index df336d8703..a36f2c97b5 100644
--- a/src/nvim/autocmd.c
+++ b/src/nvim/autocmd.c
@@ -2013,6 +2013,7 @@ char_u *getnextac(int c, void *cookie, int indent, bool do_concat)
   }
 
   AutoCmd *ac = acp->nextcmd;
+  bool oneshot = ac->once;
 
   if (p_verbose >= 9) {
     verbose_enter_scroll();
@@ -2024,7 +2025,13 @@ char_u *getnextac(int c, void *cookie, int indent, bool do_concat)
   if (ac->exec.type == CALLABLE_CB) {
     typval_T argsin = TV_INITIAL_VALUE;
     typval_T rettv = TV_INITIAL_VALUE;
-    callback_call(&ac->exec.callable.cb, 0, &argsin, &rettv);
+    if (callback_call(&ac->exec.callable.cb, 0, &argsin, &rettv)) {
+      if (ac->exec.callable.cb.type == kCallbackLua) {
+        // If a Lua callback returns 'true' then the autocommand is removed
+        oneshot = true;
+      }
+    }
+
 
     // TODO(tjdevries):
     //
@@ -2042,7 +2049,7 @@ char_u *getnextac(int c, void *cookie, int indent, bool do_concat)
   }
 
   // Remove one-shot ("once") autocmd in anticipation of its execution.
-  if (ac->once) {
+  if (oneshot) {
     aucmd_del(ac);
   }
   autocmd_nested = ac->nested;
diff --git a/src/nvim/eval.c b/src/nvim/eval.c
index af7c3d4985..33e8469768 100644
--- a/src/nvim/eval.c
+++ b/src/nvim/eval.c
@@ -7730,6 +7730,7 @@ bool callback_call(Callback *const callback, const int argcount_in, typval_T *co
   partial_T *partial;
   char_u *name;
   Array args = ARRAY_DICT_INIT;
+  Object rv;
   switch (callback->type) {
   case kCallbackFuncref:
     name = callback->data.funcref;
@@ -7742,10 +7743,13 @@ bool callback_call(Callback *const callback, const int argcount_in, typval_T *co
     break;
 
   case kCallbackLua:
-    nlua_call_ref(callback->data.luaref, NULL, args, false, NULL);
-
-    return false;
-    break;
+    rv = nlua_call_ref(callback->data.luaref, NULL, args, true, NULL);
+    switch (rv.type) {
+    case kObjectTypeBoolean:
+      return rv.data.boolean;
+    default:
+      return false;
+    }
 
   case kCallbackNone:
     return false;