api: allow nvim_buf_attach from lua using callbacks

src/nvim/api/private/defs.h

@@ -104,6 +104,7 @@ typedef enum {
   kObjectTypeString,
   kObjectTypeArray,
   kObjectTypeDictionary,
+  kObjectTypeLuaRef,
   // EXT types, cannot be split or reordered, see #EXT_OBJECT_TYPE_SHIFT
   kObjectTypeBuffer,
   kObjectTypeWindow,
@@ -119,6 +120,7 @@ struct object {
     String string;
     Array array;
     Dictionary dictionary;
+    LuaRef luaref;
   } data;
 };
 

src/nvim/api/private/helpers.c

@@ -11,6 +11,7 @@
 #include "nvim/api/private/defs.h"
 #include "nvim/api/private/handle.h"
 #include "nvim/msgpack_rpc/helpers.h"
+#include "nvim/lua/executor.h"
 #include "nvim/ascii.h"
 #include "nvim/assert.h"
 #include "nvim/vim.h"
@@ -1147,6 +1148,10 @@ void api_free_object(Object value)
       api_free_dictionary(value.data.dictionary);
       break;
 
+    case kObjectTypeLuaRef:
+      executor_free_luaref(value.data.luaref);
+      break;
+
     default:
       abort();
   }

src/nvim/api/private/helpers.h

@@ -48,6 +48,10 @@
     .type = kObjectTypeDictionary, \
     .data.dictionary = d })
 
+#define LUAREF_OBJ(r) ((Object) { \
+    .type = kObjectTypeLuaRef, \
+    .data.luaref = r })
+
 #define NIL ((Object) {.type = kObjectTypeNil})
 
 #define PUT(dict, k, v) \