From 3a67eb79825852f0f296177e837086abdbb76b6f Mon Sep 17 00:00:00 2001
From: Lucas Ritzdorf <42657792+LRitzdorf@users.noreply.github.com>
Date: Fri, 5 Jun 2026 15:20:02 -0600
Subject: [PATCH] config/lua: improve error handle-ability with Lua `require`
 (#14937)

* config/lua: make `require` throw an actual error for nonexistent modules

`require` uses pcall to catch errors and display them to the user. This
is usually okay, but it also hides errors if Lua tries to load a
nonexistent module, which the Lua config might actually want to detect
and handle on its own (e.g. by loading a different module, or disabling
functionality).

Ref #14534

* config/lua: make vanilla `require` available as `__require`

If `safeLuaRequire()`'s error-catching behavior isn't wanted, this
allows the user to call the original version directly, as `__require`.
Or, they could bring it back as the default by doing e.g.
`require = __require`, which might be desired to avoid breaking
third-party modules that want to catch errors during module load.
---
 src/config/lua/ConfigManager.cpp | 17 +++++++++++++++--
 1 file changed, 15 insertions(+), 2 deletions(-)

diff --git a/src/config/lua/ConfigManager.cpp b/src/config/lua/ConfigManager.cpp
index 309604dfb..dfbb21a59 100644
--- a/src/config/lua/ConfigManager.cpp
+++ b/src/config/lua/ConfigManager.cpp
@@ -128,6 +128,17 @@ static int safeLuaRequire(lua_State* L) {
         lua_pop(L, 1);
     }
 
+    // if we failed to resolve the require'd module, return that as an actual
+    // error (so the user can catch it via pcall)
+    {
+        std::string moduleErrPrefix = std::format("module '{}' not found", moduleName);
+        if (err.starts_with(moduleErrPrefix))
+            return luaL_error(L, err.c_str());
+    }
+
+    // otherwise, throw the error message into the config-errors list, and
+    // return an empty table to Lua (weird from a Lua perspective, but
+    // hopefully acceptable since the error is directly visible to the user)
     if (auto* mgr = CConfigManager::fromLuaState(L); mgr) {
         if (!moduleName.empty()) {
             trackRequiredLuaModulePath(L, mgr, moduleName);
@@ -138,7 +149,7 @@ static int safeLuaRequire(lua_State* L) {
 
     lua_pop(L, 1); // error object
 
-    lua_newtable(L); // fallback module
+    lua_newtable(L); // empty table as fallback return
     const int fallbackIdx = lua_gettop(L);
 
     if (!moduleName.empty()) {
@@ -322,8 +333,10 @@ void CConfigManager::reinitLuaState() {
 
     lua_getglobal(m_lua, "require");
     if (lua_isfunction(m_lua, -1)) {
+        lua_pushvalue(m_lua, -1);
+        lua_setglobal(m_lua, "__require"); // original `require` as `__require`
         lua_pushcclosure(m_lua, safeLuaRequire, 1);
-        lua_setglobal(m_lua, "require");
+        lua_setglobal(m_lua, "require"); // safe require as `require`
     } else
         lua_pop(m_lua, 1);