From 44062ebd525ec3782668ddb16709bcd152903b1e Mon Sep 17 00:00:00 2001
From: Lupus590 <lupussolitarius590@gmail.com>
Date: Fri, 8 May 2020 16:07:33 +0100
Subject: [PATCH] Allow lua REPL to warn about using local variables (#367)

`local varname = value` results in `varname` being inaccessible in
the next REPL input. This is often unintended and can lead to confusing
behaviour. We produce a warning when this occurs.
---
 src/main/resources/assets/computercraft/lua/bios.lua       | 5 +++++
 .../assets/computercraft/lua/rom/programs/lua.lua          | 7 +++++++
 2 files changed, 12 insertions(+)

diff --git a/src/main/resources/assets/computercraft/lua/bios.lua b/src/main/resources/assets/computercraft/lua/bios.lua
index 687c9c798..cef90b633 100644
--- a/src/main/resources/assets/computercraft/lua/bios.lua
+++ b/src/main/resources/assets/computercraft/lua/bios.lua
@@ -932,6 +932,11 @@ settings.define("motd.path", {
     description = [[The path to load random messages from. Should be a colon (":") separated string of file paths.]],
     type = "string",
 })
+settings.define("lua.warn_against_use_of_local", {
+    default = true,
+    description = [[Print a message when input in the Lua REPL starts with the word 'local'. Local variables defined in the Lua REPL are be inaccessable on the next input.]],
+    type = "boolean",
+})
 if term.isColour() then
     settings.define("bios.use_multishell", {
         default = true,
diff --git a/src/main/resources/assets/computercraft/lua/rom/programs/lua.lua b/src/main/resources/assets/computercraft/lua/rom/programs/lua.lua
index 5eea4dd81..b746240b9 100644
--- a/src/main/resources/assets/computercraft/lua/rom/programs/lua.lua
+++ b/src/main/resources/assets/computercraft/lua/rom/programs/lua.lua
@@ -67,6 +67,13 @@ while bRunning do
     if s:match("%S") and tCommandHistory[#tCommandHistory] ~= s then
         table.insert(tCommandHistory, s)
     end
+    if settings.get("lua.warn_against_use_of_local") and s:match("^%s*local%s+") then
+        if term.isColour() then
+            term.setTextColour(colours.yellow)
+        end
+       print("local variables from the previous input are inaccessible afterwards. If you want to be able to use a variable across multiple inputs then remove the local keyword.")
+       term.setTextColour(colours.white)
+    end
 
     local nForcePrint = 0
     local func, e = load(s, "=lua", "t", tEnv)