Syntax error in LuaLaTeX \directlua code

Question

I have the below document that I try to compile with LuaLaTex (using the MiKTeX package).

\documentclass{article}

\usepackage{pgfplots}

\pgfplotsset{compat=newest}

\begin{document}
\expandafter\pgfplotstableread\directlua {
    global json = utilities.json.load("test.json")
    tex.sprint("{\string\r")
    tex.sprint("x y\string\r")
    for n, row in ipairs(json.data) do
        tex.sprint(row[1] .. " " .. row[2] .. "\string\r")
    end
    tex.sprint("}")
}\loadedtable

\begin{tikzpicture}
  \begin{axis}
    \addplot table {\loadedtable};
  \end{axis}
\end{tikzpicture}
\end{document}

but I get a compilation error due to a Syntax error in the Lua part:

[\directlua]:1: syntax error near 'json'.
l.17 }
  \loadedtable

I'm a noob at LaTeX and unfortunately I have no clue of Lua either, but from what I have researched I can't figure out where there is a syntax error.

The respective test.json is located in the same folder like the .tex script and has this form:

{
    "name":"list_of_xy_values",
    "data":[[1,2],[2,4],[3,6],[4,3],[5,0]]
}

This question refers to this other question

Answer 1

Variables in Lua are global by default, so only local has to be explicitly stated. See a brief explanation on Lua Unofficial FAQ and Lua 5.3 Reference Manual for additional info. In LuaTeX's \directlua and luacode environments is usual to define variables as local, what you can see in Henri's answer to your other question, to avoid clashes and unexpected redefinitions. :)