Leiningen Emacs和Clojure

Question

I have a project setup at the moment that works like a charm when I use lein run . The minimal case that causes the problem is the following. I have two files, shown below. The core.clj file is supposed to throw an error and then stop. The error is simply an error that extends the standard Error of Java. However, when I open up this file in emacs and open up cider I can't get it to compile properly.

core.clj

(ns meta-clojure.core
  (:import (org.jsoup Jsoup)
           (java.lang String)
           (meta_clojure.stm RetryEx)))

(defn -main
  [& args]
  (println "Throwing exception now..")
  (throw (RetryEx. "this is broken"))
  (println "End of main")
  nil)

RetryEx.clj

(ns meta-clojure.stm.RetryEx
  (:gen-class :extends java.lang.Error))

Now, as I said, when I run the lein run command it executes just fine. However, in emacs I get the following stack trace:

clojure.lang.Compiler$CompilerException: java.lang.ClassNotFoundException: meta_clojure.stm.RetryEx, compiling:(/home/christophe/bitbucket/meta-clojure/src/meta_clojure/core.clj:1:1)
                                Compiler.java:7142 clojure.lang.Compiler.load
                                  NO_SOURCE_FILE:1 user/eval931
                                Compiler.java:6703 clojure.lang.Compiler.eval
                                Compiler.java:6666 clojure.lang.Compiler.eval
                                     core.clj:2927 clojure.core/eval
                                      main.clj:239 clojure.main/repl[fn]
                                      main.clj:239 clojure.main/repl[fn]
                                      main.clj:257 clojure.main/repl[fn]
                                      main.clj:257 clojure.main/repl
                                  RestFn.java:1523 clojure.lang.RestFn.invoke
                         interruptible_eval.clj:67 clojure.tools.nrepl.middleware.interruptible-eval/evaluate[fn]
                                      AFn.java:152 clojure.lang.AFn.applyToHelper
                                      AFn.java:144 clojure.lang.AFn.applyTo
                                      core.clj:624 clojure.core/apply
                                     core.clj:1862 clojure.core/with-bindings*
                                   RestFn.java:425 clojure.lang.RestFn.invoke
                         interruptible_eval.clj:51 clojure.tools.nrepl.middleware.interruptible-eval/evaluate
                        interruptible_eval.clj:183 clojure.tools.nrepl.middleware.interruptible-eval/interruptible-eval[fn]
                        interruptible_eval.clj:152 clojure.tools.nrepl.middleware.interruptible-eval/run-next[fn]
                                       AFn.java:22 clojure.lang.AFn.run
                      ThreadPoolExecutor.java:1145 java.util.concurrent.ThreadPoolExecutor.runWorker
                       ThreadPoolExecutor.java:615 java.util.concurrent.ThreadPoolExecutor$Worker.run
                                   Thread.java:745 java.lang.Thread.run
Caused by: java.lang.ClassNotFoundException: meta_clojure.stm.RetryEx
                           URLClassLoader.java:366 java.net.URLClassLoader$1.run
                           URLClassLoader.java:355 java.net.URLClassLoader$1.run
                                  (Unknown Source) java.security.AccessController.doPrivileged
                           URLClassLoader.java:354 java.net.URLClassLoader.findClass
                        DynamicClassLoader.java:61 clojure.lang.DynamicClassLoader.findClass
                              ClassLoader.java:425 java.lang.ClassLoader.loadClass
                              ClassLoader.java:358 java.lang.ClassLoader.loadClass
                                  (Unknown Source) java.lang.Class.forName0
                                    Class.java:191 java.lang.Class.forName
                                        core.clj:1 meta-clojure.core/eval935[fn]
                                        core.clj:1 meta-clojure.core/eval935
                                Compiler.java:6703 clojure.lang.Compiler.eval
                                Compiler.java:6692 clojure.lang.Compiler.eval
                                Compiler.java:7130 clojure.lang.Compiler.load

Could anyone help me out please? I think I need to tell Cider/Emacs to compile ahead of time or something. Perhaps leiningen compiles to different directories than emacs?

Answer 1

You are correct that you need to compile the meta-clojure.stm.RetryEx namespace to produce the class files before you can include it. This is sometimes useful if you are writing a class for consumption by a Java library and core.clj is only a test harness for developing, though it's not the easy or typical way to go about it. It is a bit more common to from with a Clojure project.

You can check what is actually been compiled by looking in the target/classes directory of the project. before compiling I see:

arthur@a:~/meta-clojure$ ls target/classes/
META-INF

Then after compiling it from the repl:

user> (compile 'meta-clojure.stm.RetryEx)
meta-clojure.stm.RetryEx
user> 
meta-clojure.core> (-main )
Throwing exception now..
RetryEx this is broken  meta-clojure.core/-main (core.clj:6)
meta-clojure.core> 

And checking the same directory:

arthur@a:~/meta-clojure$ ls -R  target/classes/
target/classes/:
meta_clojure  META-INF

target/classes/meta_clojure:
stm

target/classes/meta_clojure/stm:
RetryEx.class  RetryEx$fn__3333.class  RetryEx$fn__3351.class  RetryEx__init.class  RetryEx$loading__4958__auto__.class

target/classes/META-INF:
maven

target/classes/META-INF/maven:
meta-clojure

target/classes/META-INF/maven/meta-clojure:
meta-clojure

target/classes/META-INF/maven/meta-clojure/meta-clojure:
pom.properties

Leiningen is happy to do the AOT compiling for you, if you specify which namespaces require it:

project.clj:

(defproject meta-clojure "0.1.0-SNAPSHOT"
  :description "FIXME: write description"
  :url "http://example.com/FIXME"
  :license {:name "Eclipse Public License"
            :url "http://www.eclipse.org/legal/epl-v10.html"}
  :dependencies [[org.clojure/clojure "1.6.0"]]
  :aot [meta-clojure.stm.RetryEx])

and then run lein compile :

arthur@a:~/meta-clojure$ lein compile
Compiling meta-clojure.stm.RetryEx
arthur@a:~/meta-clojure$ ls target/classes/
meta_clojure/ META-INF/     
arthur@a:~/meta-clojure$ ls target/classes/meta_clojure/stm/

PS: you also don't need to include java.lang.String it's included by default.