Caveats

CIDER is certainly not perfect and has some limitations that everyone should be aware of.

ClojureScript limitations

Currently, the following features are not supported for ClojureScript development:

  • Reloading

  • Running tests

  • Tracing

  • Debugging (check out this ticket dedicated to porting the debugger to ClojureScript)

  • Enlighten

There is currently no support for both Clojure and ClojureScript evaluation in the same nREPL session. If Piggieback is active, code evaluation and all features will assume ClojureScript.

Microsoft Windows

Line separators

On Microsoft Windows the JVM default line separator string is \r\n which can appear in Emacs as ^M characters at the end of lines printed out by the JVM. One option is to set the buffer-display-table to not show these characters as detailed here (changing slime-repl-mode-hook to cider-repl-mode-hook). Alternatively, setting the system property line.separator to \n at JVM startup will stop the carriage return from being printed and will fix output in all cider buffers. To do so add "-Dline.separator=\"\n\"" to :jvm-opts in ~/.lein/profiles.clj.

Definition lookup in jar files

In order for source lookup commands to work with .jar files you’ll need to install either 7zip or pkunzip and add its installation folder to Emacs’s exec-path. Here’s an example:

(add-to-list 'exec-path "C:/Program Files/7-Zip")

powershell.el

The powershell inferior shell mode truncates CIDER’s REPL output when loaded. As a workaround remove

(require 'powershell)

from your Emacs config.

ClojureCLR Support

CIDER currently doesn’t support ClojureCLR. The reasons for this are the following:

  • nREPL itself runs only on the JVM (because it leverages Java APIs internally). There’s an nREPL port for ClojureCLR, but it’s not actively maintained and it doesn’t behave like the Clojure nREPL.

  • cider-nrepl uses a lot of Java code internally itself.

Those issues are not insurmountable, but are beyond the scope of our current roadmap. If someone would like to tackle them, we’d be happy to provide assistance.

Injecting dependencies and Leiningen pedantic: abort mode

Because injection currently creates an override of the nREPL dependency that Leingingen also pulls in starting up the REPL will fail if :pedantic? :abort is set. There are several ways to address this:

  • Remove the :pedantic? :abort setting.

  • Switch off injecting the dependencies with setting cider-inject-dependencies-at-jack-in to nil and provide the dependencies by editing your ~/.lein/profiles.clj as described in the standalone REPL section.

  • Adjust the value of cider-jack-in-dependencies, so it includes the same nREPL value as the one that’s bundled with Leiningen.