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List:       lua-l
Subject:    Re: Take into account __tostring whet printing _PROMPT
From:       Luiz Henrique de Figueiredo <lhf () tecgraf ! puc-rio ! br>
Date:       2020-10-22 16:10:32
Message-ID: CAD55k3p0GbJ6RROCi9GRsmXjSd2tpZhpiKG-y5b2A3p_4fAn0Q () mail ! gmail ! com
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> Why doesn't interactive Lua takes into account the __tostring metamethod
> of the non-string _PROMPT global when it prints the prompt,

Replace get_prompt in lua.c by the code below and rebuild.
It seems to work, but it hasn't been thoroughly tested.
The original code uses lua_tostring, which does not honor the
__tostring metamethod; luaL_tolstring does.

static const char *get_prompt (lua_State *L, int firstline) {
  const char *p;
  if (lua_getglobal(L, firstline ? "_PROMPT" : "_PROMPT2") == LUA_TNIL)
    p = (firstline ? LUA_PROMPT : LUA_PROMPT2);
  else {
    p = luaL_tolstring(L, -1, NULL);
    lua_remove(L, -2);  /* remove original value */
  }
  return p;
}
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