[solved] set_node error

[octacian]

I am working on a command for my mod, that update a node in the location specified through a chatcommand to the block specified. This should be pretty simple, but I'm trying to write it in a way that players don't get all the weird errors and get confused (like me), but instead get simple error messages through the chat.

I'm having two issues. When I run /update default:dirt 125 1.5 -26.2, I get "attempt to index a nil value," at line 39.

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local item_string_type = minetest.registered_items[node].type -- item string type

This line gets the type (node, craftitem, tool) for an if statement that confirms the type is node.

When I run the command the other way around, /update 125 1.5 -26.2 default:dirt, I get and error in the chat saying:

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2016-06-10 13:14:11: ERROR[Server]: Map::setNode(): Not allowing to place CONTENT_IGNORE while trying to replace "air" at (125,2,-26) (block (7,0,-2))

The /update functions accepts two values, name and param. player is then set from param, and node, p is set from param. Then I set item_string_type, for the if statement.

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  -- variables
local player = minetest.get_player_by_name(name) -- player name
local node, p = string.match(param, "^([^ ]+) *(.*)$")
local p = minetest.string_to_pos(p)
local item_string_type = minetest.registered_items[node].type -- item string type

+ The full function called by /update:

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-- Update Block
function server_tools.update_node(name, param)
  -- variables
  local player = minetest.get_player_by_name(name) -- player name
   local node, p = string.match(param, "^([^ ]+) *(.*)$")
   local p = minetest.string_to_pos(p)
   local item_string_type = minetest.registered_items[node].type -- item string type
   -- confirm node param
   if minetest.registered_items[node] == nil or minetest.registered_items[node] == "" then
      minetest.chat_send_player(name, "Invalid item string. Please try again.") --print to chat
      minetest.log("action", "[Server_Tools] "..name.." tried to update a node with invalid item string: "..item_string) --print to log
   else
      -- make sure item string is not a craftitem of tool
      if item_string_type == "tool" or item_string_type == "craftitem" then
         minetest.chat_send_player(name, "Item string cannot be a "..item_string_type) --print to chat
         minetest.log("action", "[Server_Tools] "..name.." tried to update a node to "..item_string_type) --print to log
      else
         -- confirm position params
        if p.x == "" or p.x == nil or p.y == "" or p.y == nil or p.y == nil or p.z == "" or p.z == nil then
          -- print error to chat and log
          minetest.chat_send_player(name, "Invalid position coordinates. Please try again.") -- print to chat
          minetest.log("action", "[Server_Tools] "..name.." tried to update a node using invalid coordinates.") --print to log
        else
          -- update node
            minetest.set_node(p, {name = param})
        end
      end
   end
end

You can browse the code of the whole mod here, though functions.lua is missing several small fixes that I have not committed yet because of the above issues.

[kaeza]

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minetest.set_node(p, {name = param})

You probably meant to use `node` instead of `param` here.

From your code, it seems you get (for example) `default:dirt 1,2,3` as param which you split into `node` ("[^ ]+" pattern), and `p` (".*" pattern).

A few more tips:

• `string.match` may return nil if the string does not match the pattern, so you should take that into account before passing to `string_to_pos`.
• As an extension to the above, `string_to_pos` may also return nil if it cannot parse the string as a position.
• You seem to compare `registered_nodes[node]` to both nil and a string. IIRC, registered_nodes[node] always returns a table thanks to metatables, so you should use another check to see if the node exists. Probably `rawget(minetest.registered_nodes, node) ~= nil`.
• You also seem to compare strings to numbers in `if p.x=="" ...`. This would not crash, but it will always return false.

[octacian]

Thanks!

The function now looks like this, and seems to work fine:

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-- Update Block
function servertools.update_node(name, param)
  -- variables
  local player = minetest.get_player_by_name(name) -- player name
   local node, p = string.match(param, "^([^ ]+) *(.*)$")
   local p = minetest.string_to_pos(p)

   -- confirm node param
   if minetest.registered_items[node] == nil then
      minetest.chat_send_player(name, "Please enter a valid item string.") --print to chat
      minetest.log("action", "[ServerTools] "..name.." tried to update a node with an invalid item string.") --print to log
   else
      local item_string_type = minetest.registered_items[node].type -- item string type
      -- make sure item string is not a craftitem or tool
      if item_string_type == "tool" or item_string_type == "craft" then
         minetest.chat_send_player(name, "Item string is of invalid type "..item_string_type..".") --print to chat
         minetest.log("action", "[ServerTools] "..name.." tried to update to "..item_string_type..".") --print to log
      else
         if p == nil or p == "" then
            minetest.chat_send_player(name, "Please enter valid coordinates.") --print to chat
            minetest.log("action", "[ServerTools] "..name.." tried to update a node with invalid coordinates.") --print to log
            return
         end
         -- confirm position params
        if p.x == nil or p.y == nil or p.y == nil or p.z == nil then
          -- print error to chat and log
          minetest.chat_send_player(name, "Please enter valid coordinates.") -- print to chat
          minetest.log("action", "[ServerTools] "..name.." tried to update a node with invalid coordinates.") --print to log
        else
          -- update node
            minetest.set_node(p, {name = node})
        end
      end
   end
end

If I missed something, I always appreciate knowing. PS: Check out the mod that this is for, servertools (not quite ready to post on the forums yet).