What's wrong with my lein/nrepl/emacs setup?

Question

Newbie Clojure programmer here. NREPL in Emacs isn't working for me.

• Aquamacs 2.5 (Emacs 23.4.1)
• nrepl.el 0.1.8
• Leiningen 2.2.0 on Java 1.6.0_51 Java HotSpot(TM) 64-Bit Server VM

My project is just the lein-generated Hello World.

Running "lein repl" in a shell works, but nrepl.el doesn't work. Rather than winding up in the project's namespace in the repl, I just get the default toplevel in the "user" namespace.

Should see something like:

my$ lein repl
nREPL server started on port 57347
REPL-y 0.2.0
Clojure 1.5.1
Hello Project
my.core=> 

But instead see:

; nREPL 0.1.8-preview
user> (in-ns my.core)
CompilerException java.lang.ClassNotFoundException: my.core, compiling:(NO_SOURCE_PATH:1:1)
user> 

In a clean nrepl.el scenario, I see two java processes going and they look plausible. One has my project on the -classpath and is implementing the actual repl (server), while the other is the client side java (-D MyProjectPath -m leiningen.core.main repl :headless).

I get the same lossage whether I get there by mx nrepl-jack-in or starting in the shell and then mx nrepl . I get a repl that doesn't know my project.

I wonder if this stuff works for anyone, or if I have something installed or set up wrong? Lots of "0.xxx" versions of things going on here...

Answer 1

Looks like you are missing a quote before your namespace, try the following:

(in-ns 'my.core)

Note the ' before my.

Answer 2

NRepl always starts in the top-level user namespace. Use Mx nrepl-set-ns , or Cc Mn in a Clojure buffer, to set the namespace of NRepl to the one of the buffer.

In your specific case,

• visit src/my/core.clj , press Cc Mj to start NRepl,
• switch back to the src/my/core.clj buffer,
• press Cu Cc Cz to set the NRepl namespace to my.core and switch back to the NRepl buffer.

Cu Cc Cz is a shortcut for Cc Mn followed by Cc Cz to switch to the NRepl buffer.