a simple /eval command

init.lua

@@ -0,0 +1,51 @@
+core.register_chatcommand("eval",
+    {
+        params = "<code>",
+        description = "Execute and dump value into chat",
+        privs = { server = true },
+        func = function(name, param)
+            if param == "" then
+                return false, "Gib code pls"
+            end
+            local code = "return " .. param
+
+            -- echo input back
+            core.chat_send_player(name, "> " .. code)
+
+            local func, err = loadstring(code, "usercode")
+            if not func then
+                return false, err
+            end
+
+            local ok
+            local helper = function(...)
+                -- We need this helper to access returned values
+                -- twice - to get the number and to make a table with
+                -- them.
+                --
+                -- This is a little convoluted, but it's to make sure
+                -- that evaluating functions like:
+                --
+                -- (function() return 1,nil,3 end)()
+                --
+                -- will display all returned values.
+                local n = select("#", ...)
+                local res = {...}
+                ok = res[1]
+                if n == 2 then
+                    -- returned single value or error - just return it
+                    return dump(res[2])
+                else
+                    -- returned multiple values: display one per line
+                    local ret_vals = {}
+                    for i=2, n do
+                        table.insert(ret_vals, dump(res[i]))
+                    end
+                    return table.concat(ret_vals, ',\n')
+                end
+            end
+            local res = helper(pcall(func))
+            return ok, res
+        end
+    }
+)