From f80e2cd9b19c5478d63f7da4905fc121fe6aa5ea Mon Sep 17 00:00:00 2001
From: Cloud Wu <cloudwu@gmail.com>
Date: Wed, 13 Oct 2021 12:57:55 +0800
Subject: [PATCH] bugfix: See #1484

---
 lualib-src/lua-bson.c | 27 ++++++++++++++++++---------
 1 file changed, 18 insertions(+), 9 deletions(-)

diff --git a/lualib-src/lua-bson.c b/lualib-src/lua-bson.c
index 9d20242a..517fd40e 100644
--- a/lualib-src/lua-bson.c
+++ b/lualib-src/lua-bson.c
@@ -512,16 +512,25 @@ pack_meta_dict(lua_State *L, struct bson *b, int depth) {
 
 static bool
 is_rawarray(lua_State *L) {
-	size_t len = lua_rawlen(L, -1);
-	if (len > 0) {
-		lua_pushinteger(L, len);
-		if (lua_next(L,-2) == 0) {
-			return true;
-		} else {
-			lua_pop(L,2);
-		}
+	// test first key, hash part first in Lua 5.4
+	lua_pushnil(L);
+	if (lua_next(L, -2) == 0) {
+		// empty table
+		return false;
+	}
+	lua_Integer firstkey = lua_tointeger(L, -2);
+	lua_pop(L, 2);
+	if (firstkey != 1)
+		return false;
+
+	size_t len = lua_rawlen(L, -1);
+	lua_pushinteger(L, len);
+	if (lua_next(L,-2) == 0) {
+		return true;
+	} else {
+		lua_pop(L,2);
+		return false;
 	}
-	return false;
 }
 
 static void