Resource deallocation order within MonadResource

Question

MonadResource is capable to track multiple resources. Sometimes deallocation order of these resources is important. Consider following code:

allocator1 = putStrLn "allocator1"
deallocator1 = putStrLn "deallocator1"

allocator2 = putStrLn "allocator2"
deallocator2 = putStrLn "deallocator2"

accessResource = const $ putStrLn "accessResource"

resourceTest :: MonadResource m => m ()
resourceTest = do
    (_, resource1) <- allocate allocator1 $ const deallocator1
    (_, resource2) <- allocate allocator2 $ const $ accessResource resource1 >> deallocator2
    return ()

main = runResourceT resourceTest 

Here I access resource1 from resource2 clean-up action, so I expect resource1 will always be deallocated after resource1, otherwise the code would be incorrect. And this is true at least in current implementation. If I run the code I will get:

allocator1
allocator2
accessResource
deallocator2
deallocator1

Does MonadResource always quarantine that resource allocated earlier (hence accessible from later clean-up actions) will be deallocated later, or deallocation order is implementation specific? If it implementation specific what is the best way to guarantee particular deallocation order?

Answer 1

Since version 0.3.2.1, deallocation is always in LIFO order. This was changed in respond to issue #46, which has more information. In other words, you can rely on deallocator2 always running before deallocator1.