Why is cider finding the wrong version of cider-nrepl and how can I fix it?

Question

I have installed cider via el-get, just today. When I start up cider in emacs, the following banner is printed:

; CIDER 0.8.0-snapshot (Java 1.7.0_65, Clojure 1.6.0, nREPL 0.2.6)
WARNING: The following required nREPL ops are not supported: 
eldoc ns-list ns-vars undef
Please, install (or update) cider-nrepl 0.8.0-snapshot and restart CIDER
WARNING: CIDER's version (0.8.0-snapshot) does not match cider-nrepl's version (0.7.0)
user> 

I can run my unit tests in cider, but lots of other things don't work, like doc lookup, etc. Notice that the prompt is also in the user namespace, rather than the project namespace.

My ~/.lein/profiles.clj

{:user 
 {:plugins 
  [[cider/cider-nrepl "0.7.0"]]}
}

I see that lein has downloaded what's required (and then some, strangely):

$ find ~/.m2 -name "*nrepl*"
~/.m2/repository/cider/cider-nrepl
~/.m2/repository/cider/cider-nrepl/0.8.0-SNAPSHOT/cider-nrepl-0.8.0-20140914.152356-14.jar.sha1
~/.m2/repository/cider/cider-nrepl/0.8.0-SNAPSHOT/cider-nrepl-0.8.0-20140914.152356-14.pom
~/.m2/repository/cider/cider-nrepl/0.8.0-SNAPSHOT/cider-nrepl-0.8.0-20140914.152356-14.jar
~/.m2/repository/cider/cider-nrepl/0.8.0-SNAPSHOT/cider-nrepl-0.8.0-20140914.152356-14.pom.sha1
~/.m2/repository/cider/cider-nrepl/0.8.0-SNAPSHOT/cider-nrepl-0.8.0-SNAPSHOT.pom
~/.m2/repository/cider/cider-nrepl/0.8.0-SNAPSHOT/cider-nrepl-0.8.0-SNAPSHOT.jar
~/.m2/repository/cider/cider-nrepl/0.7.0/cider-nrepl-0.7.0.jar.sha1
~/.m2/repository/cider/cider-nrepl/0.7.0/cider-nrepl-0.7.0.pom.sha1
~/.m2/repository/cider/cider-nrepl/0.7.0/cider-nrepl-0.7.0.jar
~/.m2/repository/cider/cider-nrepl/0.7.0/cider-nrepl-0.7.0.pom
~/.m2/repository/org/clojure/tools.nrepl
~/.m2/repository/org/clojure/tools.nrepl/0.2.6/tools.nrepl-0.2.6.pom.sha1
~/.m2/repository/org/clojure/tools.nrepl/0.2.6/tools.nrepl-0.2.6.pom
~/.m2/repository/org/clojure/tools.nrepl/0.2.6/tools.nrepl-0.2.6.jar.sha1
~/.m2/repository/org/clojure/tools.nrepl/0.2.6/tools.nrepl-0.2.6.jar

I also see that lein wants to bring in both cider-nrepl and tools.nrepl, although I surely don't understand why:

$ lein deps :tree
warn
 [cider/cider-nrepl "0.7.0"]
   [cljs-tooling "0.1.3" :exclusions [[org.clojure/clojure]]]
   [compliment "0.1.3" :exclusions [[org.clojure/clojure]]]
   [org.clojure/java.classpath "0.2.0" :exclusions [[org.clojure/clojure]]]
   [org.clojure/tools.namespace "0.2.5" :exclusions [[org.clojure/clojure]]]
   [org.clojure/tools.trace "0.7.8" :exclusions [[org.clojure/clojure]]]
   [org.tcrawley/dynapath "0.2.3" :exclusions [[org.clojure/clojure]]]
 [clojure-complete "0.2.3" :scope "test" :exclusions [[org.clojure/clojure]]]
 [org.clojure/clojure "1.6.0"]
 [org.clojure/tools.nrepl "0.2.6" :scope "test" :exclusions [[org.clojure/clojure]]]

Finally, my project.clj, though I am seeing this problem for all of my clojure projects:

(defproject cider-demo "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"]])

How do I get cider to pick up the correct cider-nrepl?

Answer 1

The error is presented very clearly:

WARNING: CIDER's version (0.8.0-snapshot) does not match cider-nrepl's version (0.7.0)

You need to change your profiles.clj dependency:

{:user 
 {:plugins 
  [[cider/cider-nrepl "0.8.0-SNAPSHOT"]]}
}

Or downgrade your emacs cider version to match the version of cider-nrepl you are currently asking for.

tools.nrepl isn't a problem here, and furthermore, cider actually cannot work without tools.nrepl.