From 883caff58df232c862de20427e33820f9512e598 Mon Sep 17 00:00:00 2001
From: imre84 <pentek.imre@gmail.com>
Date: Sat, 20 Apr 2024 20:00:41 +0200
Subject: [PATCH] Make //lua work with expressions as well (#243)

---
 .luacheckrc                 |  3 ++-
 WorldEdit API.md            | 14 +++++++++++---
 worldedit/code.lua          | 28 ++++++++++++++++++++--------
 worldedit_commands/init.lua | 23 +++++++++++++++++------
 4 files changed, 50 insertions(+), 18 deletions(-)

diff --git a/.luacheckrc b/.luacheckrc
index 96399b6..139c9e2 100644
--- a/.luacheckrc
+++ b/.luacheckrc
@@ -1,6 +1,7 @@
 read_globals = {"minetest", "vector", "VoxelArea", "ItemStack",
 	"table",
-	"unified_inventory", "sfinv", "smart_inventory", "inventory_plus"
+	"unified_inventory", "sfinv", "smart_inventory", "inventory_plus",
+	"dump"
 }
 globals = {"worldedit"}
 -- Ignore these errors until someone decides to fix them
diff --git a/WorldEdit API.md b/WorldEdit API.md
index fc9cf65..ae27f41 100644
--- a/WorldEdit API.md	
+++ b/WorldEdit API.md	
@@ -227,11 +227,19 @@ Code
 ----
 Contained in code.lua, this module allows arbitrary Lua code to be used with WorldEdit.
 
-### error = worldedit.lua(code)
+### error = worldedit.lua(code, name)
 
-Executes `code` as a Lua chunk in the global namespace.
+the given code gets encapsulated into a function with parameters `name`, `player`, `pos`
+where
+ * `name` is a playername or `nil`
+ * `player` is the player object of the above player if applicable, otherwise `nil`
+ * `pos` is the position of the aforementioned player (if applicable, otherwise `nil`) rounded to integers
 
-Returns an error if the code fails or nil otherwise.
+the resulting function is then executed as a Lua chunk in the global namespace.
+
+The return is
+ * a string in case of an error
+ * a tuple of `nil` and return of the function converted to a string in case of success
 
 ### error = worldedit.luatransform(pos1, pos2, code)
 
diff --git a/worldedit/code.lua b/worldedit/code.lua
index eb42e3d..f985d28 100644
--- a/worldedit/code.lua
+++ b/worldedit/code.lua
@@ -2,17 +2,29 @@
 -- @module worldedit.code
 
 --- Executes `code` as a Lua chunk in the global namespace.
--- @return An error message if the code fails, or nil on success.
-function worldedit.lua(code)
-	local func, err = loadstring(code)
-	if not func then  -- Syntax error
+-- the code will be encapsulated into a function with parameters
+--  * name (the name of the player issuing the //lua command)
+--  * player (the player object of the player)
+--  * pos (the position of the player rounded to integers)
+-- @return string in case of error, tuple of nil, return of code as string in case of success
+function worldedit.lua(code, name)
+	local factory, err = loadstring("return function(name, player, pos)\n" .. code .. "\nend")
+	if not factory then -- Syntax error
 		return err
 	end
-	local good, err = pcall(func)
-	if not good then  -- Runtime error
-		return err
+	local func = factory()
+	local player, pos
+	if name then
+		player = minetest.get_player_by_name(name)
+		if player then
+			pos = vector.round(player:get_pos())
+		end
 	end
-	return nil
+	local good, err = pcall(func, name, player, pos)
+	if not good then -- Runtime error
+		return tostring(err)
+	end
+	return nil, dump(err)
 end
 
 
diff --git a/worldedit_commands/init.lua b/worldedit_commands/init.lua
index fc67e5a..bf91bce 100644
--- a/worldedit_commands/init.lua
+++ b/worldedit_commands/init.lua
@@ -1555,16 +1555,27 @@ worldedit.register_command("lua", {
 	description = S("Executes <code> as a Lua chunk in the global namespace"),
 	privs = {worldedit=true, server=true},
 	parse = function(param)
+		if param == "" then
+			return false
+		end
 		return true, param
 	end,
 	func = function(name, param)
-		local err = worldedit.lua(param)
-		if err then
-			worldedit.player_notify(name, "code error: " .. err)
-			minetest.log("action", name.." tried to execute "..param)
+		-- shorthand like in the Lua interpreter
+		if param:sub(1, 1) == "=" then
+			param = "return " .. param:sub(2)
+		end
+		local err, ret = worldedit.lua(param, name)
+		if err == nil then
+			minetest.log("action", name .. " executed " .. param)
+			if ret ~= "nil" then
+				worldedit.player_notify(name, "code successfully executed, returned " .. ret)
+			else
+				worldedit.player_notify(name, "code successfully executed")
+			end
 		else
-			worldedit.player_notify(name, "code successfully executed", false)
-			minetest.log("action", name.." executed "..param)
+			minetest.log("action", name .. " tried to execute " .. param)
+			worldedit.player_notify(name, "code error: " .. err)
 		end
 	end,
 })