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Roma 2026-03-13T16:20:51.605269Z
After upgrading to core.async 1.9.847-alpha3 one of my flows stopped working with the following error:
java.lang.NullPointerException: Cannot invoke "java.util.concurrent.Future.get(long, java.util.concurrent.TimeUnit)" because the return value of "clojure.lang.IFn.invoke(Object, Object, Object)" is null
at clojure.core.async.flow.impl$proc$reify__41362$fn__41365.invoke(impl.clj:257)
at clojure.core.async.flow.impl$proc$reify__41362$run__41367$fn__41373.invoke(impl.clj:302)
at clojure.core.async.flow.impl$proc$reify__41362$run__41367.invoke(impl.clj:279)
at clojure.lang.AFn.applyToHelper(AFn.java:152)
at clojure.lang.AFn.applyTo(AFn.java:144)
at clojure.core$apply.invokeStatic(core.clj:667)
at clojure.core$apply.invoke(core.clj:662)
at clojure.core.async.flow.impl$futurize$fn__41156$fn__41157.invoke(impl.clj:34)
at clojure.lang.AFn.run(AFn.java:22)
at java.base/java.lang.VirtualThread.run(VirtualThread.java:456)
Alex Miller (Clojure team) 2026-03-13T16:34:04.989089Z
that is interesting, I'll ping @fogus to take a look at that (although I think he is offline today)
2026-03-13T16:41:36.601089Z
https://github.com/clojure/core.async/commit/93df4d0ff4146ca9c94ba005af14da0c7b37bc42#diff-db86219cca929c54c580646afd2d4cf5e27262ca617e0ec068af5113d98bb029R29-L31 execute returns nil, submit returns a future
Alex Miller (Clojure team) 2026-03-13T18:10:42.066109Z
that is related to some stuff we're doing in ASYNC-270 that Fogus is already working on. I did not realize it was affecting flow however. we will definitely prioritize getting that fixed asap.