src/lauxlib.js: e argument is not compulsory

e.g. when file:write fails due to short write

1 files changed, 11 insertions, 3 deletions

diff --git a/src/lauxlib.js b/src/lauxlib.js
index 1300f2a..2276bd0 100644
--- a/src/lauxlib.js
+++ b/src/lauxlib.js
@@ -290,11 +290,19 @@ const luaL_fileresult = function(L, stat, fname, e) {
         return 1;
     } else {
         lua_pushnil(L);
+        let message, errno;
+        if (e) {
+            message = e.message;
+            errno = -e.errno;
+        } else {
+            message = "Success"; /* what strerror(0) returns */
+            errno = 0;
+        }
         if (fname)
-            lua_pushfstring(L, to_luastring("%s: %s"), fname, to_luastring(e.message));
+            lua_pushfstring(L, to_luastring("%s: %s"), fname, to_luastring(message));
         else
-            lua_pushstring(L, to_luastring(e.message));
-        lua_pushinteger(L, -e.errno);
+            lua_pushstring(L, to_luastring(message));
+        lua_pushinteger(L, errno);
         return 3;
     }
 };