Consider supporting IDeref "interface" implementation in defrecord

[borkdude]

@djblue has already made a start with this, which is merged to the IDeref branch. One remaining problem is how can we simultaneously have IDeref as a real Java class in sci (probably mainly for supporting (instance? IDeref x) and also let people implement it e.g. in defrecord, like protocols in sci (which are implemented using multimethods).

We currently represent protocols as maps with a set of methods in them:

https://github.com/borkdude/babashka/blob/5d9027fe0a41ff1d1e9db124514ad257f1982fe5/src/babashka/impl/protocols.clj#L33

We could add the interface class to that protocol. So when we resolve a class name and we really want a class, but we get a map, we can look in that map and get the class out of it. In other cases where we expect the class to behave more like the protocol we can handle it like the protocol.

[djblue]

With the following code:

(defrecord Example []
  clojure.lang.IDeref
  (deref [this] :deref)

  clojure.lang.IAtom
  (reset [this new-value] :reset)

  (swap  [this f]          :swap)
  (swap  [this f a]        :swap)
  (swap  [this f a b]      :swap)
  (swap  [this f a b args] :swap)

  (compareAndSet [this oldv newv] :compare-and-set))

I get this error:

----- Context ------------------------------------------------------------------
1: (defrecord Example []
   ^--- No implementation of method: :getName of protocol: #'sci.impl.vars/HasName found for class: nil
2:   IDeref
3:   (deref [this] :deref)
4:
5:   IAtom
6:   (reset [this new-value] :reset)

----- Stack trace --------------------------------------------------------------

[borkdude]

Thanks. This example works for me:

(defrecord Example []
  clojure.lang.IDeref
  (deref [this] :deref)
  clojure.lang.IAtom
  (reset [this new-value] :reset)
  (swap  [this f]          :swap)
  #_(swap  [this f a]        :swap)
  #_(swap  [this f a b]      :swap)
  #_(swap  [this f a b args] :swap)
  #_(compareAndSet [this oldv newv] :compare-and-set))
(prn @(->Example))
(prn (reset! (->Example) 1))
(prn (swap! (->Example) inc))

but there is a problem with multi-arity implementations. Also I didn't add compareAndSet yet. I'll let you know when this is fixed.

PS: make sure to update both bb and sci and run lein clean after compilation with GraalVM. Also, just for trying you can also invoke lein bb or make a clojure alias which invokes bb from the JVM.

[borkdude]

@djblue On the latest bb /sci IDeref branch:

https://11627-201467090-gh.circle-artifacts.com/0/release/babashka-0.2.1-SNAPSHOT-macos-amd64.zip

(defrecord Example []
  clojure.lang.IDeref
  (deref [this] :deref)

  clojure.lang.IAtom
  (reset [this new-value] :reset)

  (swap  [this f]          :swap)
  (swap  [this f a]        :swap)
  (swap  [this f a b]      :swap)
  (swap  [this f a b args] :swap)

  (compareAndSet [this oldv newv] :compare-and-set))

[@(->Example)
 (reset! (->Example) 1)
 (swap! (->Example) inc)
 (swap! (->Example) + 1)
 (swap! (->Example) + 1 2)
 (swap! (->Example) + 1 2 3)
 (compare-and-set! (->Example) 1 2)]

$ ~/Downloads/bb-ideref /tmp/foo.clj
[:deref :reset :swap :swap :swap :swap :compare-and-set]

[djblue]

@borkdude, this works perfectly for me!

[borkdude]

@djblue Now also added IAtom2 to both branches. Will merge with master later today.