some quality of life features for using global vars

README.md

@@ -18,6 +18,7 @@ Outputs this:
 This also just works:
 ```
 > x = 2*2
+
 > x
 | 4
 ```
@@ -44,6 +45,7 @@ No need to use `core.chat_send_player()`, just use `print()` - it will do the ri
 
 ```
 > objs = core.get_objects_inside_radius(here, 10)
+
 > for i,o in ipairs(objs) do print(i, (o:get_luaentity() or {}).name, o:get_pos()) end
 < 1 nil (-98.0, 15.5, 33.4)
 < 2 mobs_animal:kitten (-101.0, 16.5, 30.0)
@@ -80,9 +82,12 @@ Show indices for easier manual access:
 |  [1] = #<player: "singleplayer">,
 |  [2] = #<luaentity: "mobs_animal:kitten">,
 | }
+
 > _[2]
 | #<luaentity: "mobs_animal:kitten">
+
 > pos = _:get_pos()
+
 > pos
 | {
 |  x = 123.5,
@@ -91,3 +96,42 @@ Show indices for easier manual access:
 | }
 ```
 
+### Accessing and changing global variables
+You can save some keypresses by not typing `local` in front of every
+variable. Assigning to globals won't clobber them, instead using your personal
+environment. But you can still read globals as usual.
+
+```
+> print(myvar)
+* Accessing undeclared variable: "myvar"
+< nil
+
+> myvar = 1
+| Done.
+
+> print(myvar)
+< 1
+| Done.
+```
+
+If you want to create a new global or actually overwrite existing one,
+you can access global environment through usual `_G` or `global`
+variables. Using them will print a message telling you if global var
+already existed.
+
+```
+> cmd_eval = nil
+| Done.
+
+> cmd_eval  -- accesses real global
+{
+  e = { ... }, ...
+}
+
+> global.cmd_eval = nil
+* Overwriting global: "cmd_eval"
+| Done.
+
+> cmd_eval
+| nil       -- wiped for real
+```

init.lua

@@ -11,6 +11,11 @@ _G[MODNAME] = api
 api.e = {}
 
 
+local function orange_fmt(...)
+    return core.colorize("#FFA91F", string.format(...))
+end
+
+
 local function create_shared_environment(player_name)
     local magic_keys = {
         -- These are _functions_ pretending to be _variables_, they will
@@ -53,6 +58,21 @@ local function create_shared_environment(player_name)
     }
 
     local g = {} -- "do not warn again" flags
+    local global_proxy = setmetatable(
+        {"<proxy>"},
+        {
+            __index = _G,
+            __newindex = function(t, k, v)
+                if _G[k] then
+                    core.chat_send_player(player_name, orange_fmt("* Overwriting global: %s", dump(k)))
+                else
+                    core.chat_send_player(player_name, orange_fmt("* Creating new global: %s", dump(k)))
+                        end
+                _G[k] = v
+            end,
+        }
+    )
+
     local eval_env = setmetatable(
         {
             my_name = player_name,
@@ -64,22 +84,29 @@ local function create_shared_environment(player_name)
                 end
                 core.chat_send_player(player_name, msg)
             end,
-            dump = repl_dump,
+            --global = _G, -- this works, but dumps whole global env if you just print `cmd_eval` value
+            _G = global_proxy, -- use our proxy to get warnings
+            global = global_proxy, -- just a different name for globals
+            --dump = repl_dump,
         },
         {
             __index = function(self, key)
+                -- we give warnings on accessing undeclared var because it's likely a typo
                 local res = rawget(_G, key)
                 if res == nil then
                     local magic = magic_keys[key]
                     if magic then
                         return magic()
                     elseif not g[key] then
-                        core.chat_send_player(player_name, string.format("* Accessing undeclared variable: '%s'", key))
+                        core.chat_send_player(player_name, orange_fmt("* Accessing undeclared variable: %s", dump(key)))
                         g[key] = true -- warn only once
                     end
                 end
                 return res
             end
+            -- there's no __newindex method because we allow assigning
+            -- "globals" inside snippets, since those will be only
+            -- accessible to eval and stored in `eval_env`
         }
     )
     return eval_env

todo.org

@@ -16,3 +16,5 @@ copy relevant parts from there.
 * add proper REPL
 Register on chat message and let executing multiple commands without
 typing `/eval`.  Maybe via `/repl` command...
+* add a "pager" for long output
+To not spam the chat and prevent "Internal error: String too long"