With the latest Git revision on SBCL 1.0.51, when trying to migrate objects that have a derived slot, elephant tries to call setf slot-value-using-class on the derived slot, resulting in an error : "Cannot write computed (derived) slot... for read/index retrieval only".
It seems to me that copy-persistent-slots shouldn't try to write derived slots, as the work will be done when (setf slot-value-using-class) is called on the slots the derived function depends on. So I tried to patch the code for that (see attached patch). This seems to do the trick in that the migration works. I stumble upon another problem though : the derived slots are unbound after migration. Apparently, update-derived-slots is called when copying slot values, but derived-slots-trigger seems to always return nil... I don't get why. Here's my test case if anyone is interested (notice that I need to require bordeaux-threads manually, which is probably a small dependency bug ?). The first describe shows c=3, as expected, while the second describe shows c unbound. (require 'elephant) (require 'bordeaux-threads) (use-package 'elephant) (defvar *store1* (open-store '(:BDB "store1"))) (defvar *store2* (open-store '(:BDB "store2"))) (defpclass test () ((a :type integer :accessor a :initarg :a) (b :type integer :accessor b :initarg :b) (c :derived-fn (λ (obj) (values (+ (a obj) (b obj)) t))))) (let ((*store-controller* *store1*)) (describe (make-instance 'test :a 1 :b 2))) (migrate *store2* *store1*) (close-store *store1*) (describe (first (get-instances-by-class 'test)))
patch_migrate_derived
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