Clojurians Log v2

@weavejester FYI: https://github.com/RickMoynihan/redef-methods

I haven’t created an official release yet — currently trialing it out. Any comments greatfully received.

@rickmoynihan Looks pretty reasonable, and a good tool for stubbing out multimethods. When you're happy with it, submit it to the Clojure toolbox and I'll add it to the directory 🙂

cool

my main issue with it, which I still need to investigate more fully is how it interacts with ig/load-namespaces

I haven’t fully debugged it yet… but it looked very much like if the method bodies aren’t loaded before you with-redef-methods it - then you’d get a classcast exception

I see what you mean... If a defmethod is hit for an overridden multimethod.

so I had to resort to loading the namespaces by hand, before redef-ing them. I’m guessing because load-namespaces replaces the var

yeah

I don't think load-namespaces replaces the var... since the var would be integrant.core/init-key, which should already be loaded, because load-namespaces is in integrant.core.

yeah you’re right — it’s the internals of the defmethod though

But what it will do is call defmethod on init-key, so it expects init-key to be a multimethod.

Okay, so defmethod expects a clojure.lang.MultiFn...

not sure quite what you’re saying… what I’m saying is that the internals of a multi are mutable state too

yeah

that was the ClassCastException

not got a repl open just now

was meaning to isolate the causes in a minimal harness

ahh right enough there’s a :tag hint

So I think I'd copy the multimethod... like, (clojure.lang.MultiFn. (.name m) (.dispatchFn m) (.defaultDispatchVal m) (.hierarchy m))

Since they're all public members: https://github.com/clojure/clojure/blob/master/src/jvm/clojure/lang/MultiFn.java

yeah was just thinking something like that would be the solution

thanks

And then override the copied MultiFn by adding your own .addMethod.

really? I avoid mutating anything just now

Maybe set up a default dispatch that goes back to the original?

does that already

Even though you'd be mutating the MultiFn clone, you'd be throwing away the clone afterwards.

Like:

(defn clone-multimethod [m]
  (let [m' (clojure.lang.MultiFn. (.name m) ...)]
    (doseq [[k f] (methods m)]
      (.addMethod m' k f))
    m'))

Or just add a default dispatch going back to the original, maybe:

(defn clone-multimethod [m]
  (let [m' (clojure.lang.MultiFn. (.name m) ...)]
    (.addMethod m' (.defaultDispatchVal m) m)
    m'))

Although... I guess you'd want a proxy of the MultiFn, so you could ensure that .addMethod doesn't override the stuff you've overridden yourself.

Perhaps at that point it's better to go back to Java and inherit a new class from the old... unless proxy does that for us. I can't remember if it keeps inherited methods or not.

sorry had to rush off out… will have a look and think