clojure.tools/namespace refresh fails with "No namespace: foo"

Question

I'm using tools.namespace to provide smart reloading of namespaces on the REPL. However, when calling refresh or refresh-all, it throws an error.

user=> (require '[clojure.tools.namespace.repl :as tn])
user=> (tn/refresh)
:reloading (ep31.common ep31.routes ep31.config ep31.application user ep31.common-test ep31.example-test)
:error-while-loading user

java.lang.Exception: No namespace: ep31.config, compiling:(user.clj:1:1)

And it seems to end up in this weird state where (require ep31.config) works without an error, but afterwards the namespace isn't actually defined.

Arne Brasseur · Accepted Answer · 2017-05-29 16:49:11Z

12

I kind of figured this out, this seems to be a combination of circumstances

there were AOT compiled classes left in target/classes from doing lein uberjar previously
tools.namespace doesn't function correctly when loaded namespaces are AOT compiled
target/classes is by default on the classpath

So long story short, if you did a jar/uberjar build before, then remove target/ and things should start working again.

The question I haven't been able to solve yet is why target/classes is on the classpath to begin with. I'm suspecting it's being added by Leiningen, but haven't found yet where or why it's happening.

answered May 29, 2017 at 16:49

Arne Brasseur

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3 Comments

Alessandra Sierra Over a year ago

This is correct. Leiningen puts target/classes on the classpath by default for two reasons: 1) to make compiled Java sources available to the application, and 2) the output directory for AOT-compilation (*compile-path*) must be on the classpath.

Chris Murphy Over a year ago

So if you did a lein clean after doing lein uberjar you would not encounter your problem? Or rather did lein clean as soon as you got into a bad state such as described in your question.

The Alchemist Over a year ago

I deleted my build/clojure directory (I'm using the gradle plugin) and restarted my REPL and that fixed it.

Viesti · Accepted Answer · 2018-02-10 13:20:57Z

3

I learned this the hard way, documentation for :target-path says (https://github.com/technomancy/leiningen/blob/master/sample.project.clj#L309-L313):

;; All generated files will be placed in :target-path. In order to avoid
;; cross-profile contamination (for instance, uberjar classes interfering
;; with development), it's recommended to include %s in in your custom
;; :target-path, which will splice in names of the currently active profiles.
:target-path "target/%s/"

I guess there has to be legacy reasons that :target-path "target/%s/" isn't the default.

edited Feb 10, 2018 at 13:20

answered Feb 9, 2018 at 21:17

Viesti

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2 Comments

Thomas Smyth Over a year ago

While this link may answer the question, it is better to include the essential parts of the answer here and provide the link for reference. Link-only answers can become invalid if the linked page changes. - From Review

Viesti Over a year ago

Good point! Included the documentation for :target-path, now the answer should make more sense (the documentation is quite succinct on describing the problem).

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