Returning handles would introduce subtle memory management issues because the garbage collector wouldn't know which objects it should keep alive. With the stack-based API the user can only ever interact with objects that are on the stack and thus are kept alive by the garbage collector. The Lua authors explain this in the following article:
https://queue.acm.org/detail.cfm?id=1983083
I would agree that the Lua C API itself is not very eegonomic, but the wrappers/bindings it enables absolutely are! For example, integrating Lua in C++ with sol2 is an absolute joy.
Yes it could pin accessed objects in some arena, like idk... "stack", for the duration of the call. And release it after an "invocation" returns, or if the host requests it explicitly. It's almost like my example already mentioned it near "everything but ref’d things disappears here" (/s).
I understand how gcs work and their nuances. My only problem was with the "fantastic" part. Lua stack is not "not ergonomic", but absolutely shit to work with, and "there's wrappers" is not an argument, cause they are not a part of distribution but external projects ought to fix the mess.
I would agree that the Lua C API itself is not very eegonomic, but the wrappers/bindings it enables absolutely are! For example, integrating Lua in C++ with sol2 is an absolute joy.