@bozhidar following the new release of lein (2.8.3), I now get this on a project configured with lein and CIDER:

❯ lein repl
[WARNING] No nREPL middleware descriptor in metadata of #'cider.piggieback/wrap-cljs-repl, see nrepl.middleware/set-descriptor!
nREPL server started on port 41553 on host 127.0.0.1 - 
ERROR: Unhandled REPL handler exception processing message {:id b103d5eb-0dad-4eca-90a6-dbce5a8be1da, :op clone}
java.lang.NullPointerException
	at clojure.core$deref_future.invokeStatic(core.clj:2292)
	at clojure.core$deref.invokeStatic(core.clj:2312)
	at clojure.core$deref.invoke(core.clj:2298)
	at cider.piggieback$wrap_cljs_repl$fn__22856.invoke(piggieback.clj:274)
	at clojure.tools.nrepl.middleware$wrap_conj_descriptor$fn__15275.invoke(middleware.clj:22)
	at nrepl.server$handle_STAR_.invokeStatic(server.clj:18)
	at nrepl.server$handle_STAR_.invoke(server.clj:15)
	at nrepl.server$handle$fn__14240.invoke(server.clj:27)
	at clojure.core$binding_conveyor_fn$fn__5476.invoke(core.clj:2022)
	at clojure.lang.AFn.call(AFn.java:18)
	at java.util.concurrent.FutureTask.run(FutureTask.java:266)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
	at java.lang.Thread.run(Thread.java:748)

Do you want me to file an issue? (Which one, though, CIDER or nREPL or lein? 🙂)

@manuel What’s your middleware version?

It’s certainly not a lein issue anymore - I see some reference to the legacy tools.nrepl, so I assume you’ve got some legacy dependency somewhere.

let me check

@bozhidar you're right. Upgraded all the outdated dependencies in the project, now lein repl works as expected. Thanks for the tip.

Any time!

It’s important for people to be on a recent piggieback, cider-nrepl and friends, as support for the modern nREPL was added relatively recently.