Lua aligned plain-text table renderer

local function render_table(headers, rows)
  local w = {}
  for i, h in ipairs(headers) do w[i] = #tostring(h) end
  for _, row in ipairs(rows) do
    for i, cell in ipairs(row) do w[i] = math.max(w[i] or 0, #tostring(cell)) end
  end
  local function fmt(cells)
    local parts = {}
    for i, cell in ipairs(cells) do
      parts[i] = tostring(cell) .. string.rep(' ', w[i] - #tostring(cell) + 2)
    end
    return (table.concat(parts):gsub('%s+$', ''))
  end
  local dashes = {}
  for i = 1, #headers do dashes[i] = string.rep('-', w[i]) end
  local out = { fmt(headers), fmt(dashes) }
  for _, row in ipairs(rows) do out[#out + 1] = fmt(row) end
  return table.concat(out, '\n')
end

return render_table