ansi namespace attempts to require nrepl.core, causes exceptions in some cases

[ptaoussanis]

@hlship Hi Howard, thanks for all your work on Pretty!

I have an issue to report, involving an apparent interaction between recent versions of Pretty, and cider-nrepl.

Quick info:

• I author a library called Timbre, which includes Pretty as a dependency.
• A Timbre user reported a strange error that had appeared after a Timbre update.
• On further digging, I managed to create a minimal reproducible showing that the issue actually seems to have been triggered by the update of Pretty from version 1.1.1 to 1.3.
• The reproducible reliably shows the issue on my system with [io.aviso/pretty "1.3"] and [io.aviso/pretty "1.4.4"], but not with [io.aviso/pretty "1.1.1"].
• The reproducible includes only Pretty and cider-nrepl, nothing else - so it looks like this might be a problem either with Pretty, or that Pretty is triggering an issue with cider-nrepl.

Instructions to reproduce

1. Clone the minimum reproducible project.
2. Run lein repl
3. Try to evaluate (require '[beholder.handlers] :reload-all)

On my system this reliably generates the following error:

Exception updating the ns-cache #error {
 :cause No implementation of method: :send of protocol: #'nrepl.transport/Transport found for class: nrepl.middleware.caught$caught_transport$reify__1208
 :via
 [{:type java.lang.IllegalArgumentException
   :message No implementation of method: :send of protocol: #'nrepl.transport/Transport found for class: nrepl.middleware.caught$caught_transport$reify__1208
   :at [clojure.core$_cache_protocol_fn invokeStatic core_deftype.clj 584]}]
 :trace
 [[clojure.core$_cache_protocol_fn invokeStatic core_deftype.clj 584]
  [clojure.core$_cache_protocol_fn invoke core_deftype.clj 576]
  [nrepl.transport$eval7719$fn__7737$G__7710__7744 invoke transport.clj 23]
  [clojure.lang.Var invoke Var.java 388]
  [cider.nrepl.middleware.track_state$update_and_send_cache$fn__4360 invoke track_state.clj 213]
  [cider.nrepl.middleware.track_state$update_and_send_cache invokeStatic track_state.clj 209]
  [cider.nrepl.middleware.track_state$update_and_send_cache invoke track_state.clj 159]
  [cider.nrepl.middleware.track_state$update_and_send_cache invokeStatic track_state.clj 181]
  [cider.nrepl.middleware.track_state$update_and_send_cache invoke track_state.clj 159]
  [clojure.lang.AFn applyToHelper AFn.java 156]
  [clojure.lang.AFn applyTo AFn.java 144]
  [clojure.core$apply invokeStatic core.clj 669]
  [clojure.core$update_in$up__6922 invoke core.clj 6220]
  [clojure.core$update_in invokeStatic core.clj 6221]
  [clojure.core$update_in doInvoke core.clj 6207]
  [clojure.lang.RestFn applyTo RestFn.java 146]
  [clojure.core$apply invokeStatic core.clj 673]
  [clojure.core$binding_conveyor_fn$fn__5823 doInvoke core.clj 2058]
  [clojure.lang.RestFn applyTo RestFn.java 146]
  [clojure.lang.Agent$Action doRun Agent.java 114]
  [clojure.lang.Agent$Action run Agent.java 163]
  [java.util.concurrent.ThreadPoolExecutor runWorker ThreadPoolExecutor.java 1144]
  [java.util.concurrent.ThreadPoolExecutor$Worker run ThreadPoolExecutor.java 642]
  [java.lang.Thread run Thread.java 1589]]}

Do you have any ideas what might have changed since 1.1.1 to cause this?
I couldn't find any related open or closed issues.

Thanks for any assistance! Cheers :-)

[hlship]

This is almost certainly related to the code in the ansi namespace that attempts to determine whether to enable colors or not; it checks to see if namespace nrepl.core is present.

[hlship]

Looking into this now; I've wired up your sample project to the org.clj-commons/pretty source and can reproduce your error. When I comment out the (is-ns-available? 'nrepl.core) part, it works fine.

[hlship]

Using Namespace/find instead of require seems to work.

[ptaoussanis]

That's great news Howard, thanks so much for your help on this - and your work on Pretty in general!

Cheers :-)