Remove dependency on _G["package"]

4 files changed, 44 insertions, 8 deletions

diff --git a/src/compat.cpp b/src/compat.cpp
index 591e19f..6ceed8f 100644
--- a/src/compat.cpp
+++ b/src/compat.cpp
@@ -6,6 +6,23 @@
 #include "macros_and_utils.h"
 
 // #################################################################################################
+
+// a small helper to obtain the "package" module table from the registry instead of relying on the presence of _G.package
+int luaG_getpackage(lua_State* L_)
+{
+    STACK_CHECK_START_REL(L_, 0);
+    int type{ lua503_getfield(L_, LUA_REGISTRYINDEX, LUA_LOADED_TABLE) };                          // L_: _R._LOADED|nil
+    if (type != LUA_TTABLE) {                                                                      // L_: _R._LOADED|nil
+        STACK_CHECK(L_, 1);
+        return type;
+    }
+    type = lua503_getfield(L_, -1, LUA_LOADLIBNAME);                                               // L_: _R._LOADED package|nil
+    lua_remove(L_, -2);                                                                            // L_: package|nil
+    STACK_CHECK(L_, 1);
+    return type;
+}
+
+// #################################################################################################
 // #################################################################################################
 #if LUA_VERSION_NUM == 501
 // #################################################################################################
@@ -71,7 +88,7 @@ int lua_getiuservalue(lua_State* L_, int idx_, int n_)
 
 #if LUA_VERSION_NUM == 501
     /* default environment is not a nil (see lua_getfenv) */
-    lua_getglobal(L_, "package");
+    lua_getglobal(L_, LUA_LOADLIBNAME);
     if (lua_rawequal(L_, -2, -1) || lua_rawequal(L_, -2, LUA_GLOBALSINDEX)) {
         lua_pop(L_, 2);
         lua_pushnil(L_);
diff --git a/src/compat.h b/src/compat.h
index 4816cb7..f98e142 100644
--- a/src/compat.h
+++ b/src/compat.h
@@ -100,6 +100,25 @@ inline int lua504_dump(lua_State* L_, lua_Writer writer_, void* data_, [[maybe_u
 
 // #################################################################################################
 
+#if LUA_VERSION_NUM < 503
+// starting with Lua 5.3, lua_getfield returns the type of the value it found
+inline int lua503_getfield(lua_State* L_, int idx_, char const* k_)
+{
+    lua_getfield(L_, idx_, k_);
+    return lua_type(L_, -1);
+}
+
+#else // LUA_VERSION_NUM >= 503
+
+inline int lua503_getfield(lua_State* L_, int idx_, char const* k_)
+{
+    return lua_getfield(L_, idx_, k_);
+}
+
+#endif // LUA_VERSION_NUM >= 503
+
+// #################################################################################################
+
 // wrap Lua 5.3 calls under Lua 5.1 API when it is simpler that way
 #if LUA_VERSION_NUM == 503
 
@@ -199,3 +218,5 @@ inline char const* lua_typename(lua_State* L_, LuaType t_)
 {
     return lua_typename(L_, static_cast<int>(t_));
 }
+
+int luaG_getpackage(lua_State* L_);
diff --git a/src/keeper.cpp b/src/keeper.cpp
index 763bcf7..8e76247 100644
--- a/src/keeper.cpp
+++ b/src/keeper.cpp
@@ -651,15 +651,14 @@ void init_keepers(Universe* U_, lua_State* L_)
 
         // make sure 'package' is initialized in keeper states, so that we have require()
         // this because this is needed when transferring deep userdata object
-        luaL_requiref(K, "package", luaopen_package, 1);                                           // L_: settings                                    K: package
+        luaL_requiref(K, LUA_LOADLIBNAME, luaopen_package, 1);                                     // L_: settings                                    K: package
         lua_pop(K, 1);                                                                             // L_: settings                                    K:
         STACK_CHECK(K, 0);
         serialize_require(DEBUGSPEW_PARAM_COMMA(U_) K);
         STACK_CHECK(K, 0);
 
-        // copy package.path and package.cpath from the source state (TODO: use _R._LOADED.package instead of _G.package)
-        lua_getglobal(L_, "package");                                                              // L_: settings package                            K:
-        if (!lua_isnil(L_, -1)) {
+        // copy package.path and package.cpath from the source state
+        if (luaG_getpackage(L_) != LUA_TNIL) {                                                     // L_: settings package                            K:
             // when copying with mode LookupMode::ToKeeper, error message is pushed at the top of the stack, not raised immediately
             InterCopyContext c{ U_, DestState{ K }, SourceState{ L_ }, {}, SourceIndex{ lua_absindex(L_, -1) }, {}, LookupMode::ToKeeper, {} };
             if (c.inter_copy_package() != InterCopyResult::Success) {                              // L_: settings ... error_msg                      K:
diff --git a/src/tools.cpp b/src/tools.cpp
index a55ee75..049a065 100644
--- a/src/tools.cpp
+++ b/src/tools.cpp
@@ -1826,12 +1826,11 @@ void InterCopyContext::inter_copy_keyvaluepair() const
         STACK_CHECK(L1, 1);
         // raise the error when copying from lane to lane, else just leave it on the stack to be raised later
         if (mode == LookupMode::LaneBody) {
-            raise_lua_error(getErrL());
+            raise_lua_error(getErrL()); // that's ok, getErrL() is L1 in that case
         }
         return InterCopyResult::Error;
     }
-    lua_getglobal(L2, "package"); // TODO: use _R._LOADED.package instead of _G.package
-    if (lua_isnil(L2, -1)) { // package library not loaded: do nothing
+    if (luaG_getpackage(L2) == LUA_TNIL) { // package library not loaded: do nothing
         DEBUGSPEW_CODE(fprintf(stderr, INDENT_BEGIN "'package' not loaded, nothing to do\n" INDENT_END(U)));
         STACK_CHECK(L1, 0);
         return InterCopyResult::Success;