Basic Configuration

Like Emacs itself, almost every part of CIDER is configurable. The CIDER developers have tried to implement some reasonable defaults that should work for a large portion of the Clojure community, but we know that there is nothing approaching a "one size fits all" development environment and we've tried to create points of customization that can account for many different peoples' preferences. In this way, you should be able to make CIDER as comfortable as possible for you.

You can see every single customizable configuration option with the command M-x customize-group RET cider.

This section doesn't describe every possible customization that CIDER offers, but here are some of the most popular.

Disable Automatic cider-mode in clojure-mode Buffers

By default, CIDER enables cider-mode in all clojure-mode buffers after it establishes the first CIDER connection. It will also add a clojure-mode hook to enable cider-mode on newly-created clojure-mode buffers. You can override this behavior, however:

(setq cider-auto-mode nil)

Disable Symbol Confirmation

By default, CIDER prompts you for a symbol when it executes interactive commands that require a symbol (e.g. cider-doc). The default symbol will be the one at point. If you set cider-prompt-for-symbol to nil, CIDER will try the symbol at point first, and only prompt if that fails (this was the behavior in older CIDER releases).

(setq cider-prompt-for-symbol nil)

Log nREPL Communications

If you want to see all communications between CIDER and the nREPL server:

(setq nrepl-log-messages t)

CIDER will then create buffers named *nrepl-messages conn-name* for each connection.

The communication log is tremendously valuable for debugging CIDER-to-nREPL problems and we recommend you enable it when you are facing such issues.

Hide Special nREPL Buffers

If you're finding that *nrepl-connection* and *nrepl-server* buffers are cluttering up your development environment, you can suppress them from appearing in some buffer switching commands like switch-to-buffer(C-x b):

(setq nrepl-hide-special-buffers t)

If you need to make the hidden buffers appear When using switch-to-buffer, type SPC after issuing the command. The hidden buffers will always be visible in list-buffers (C-x C-b).

Prefer Local Resources Over Remote Resources

To prefer local resources to remote resources (tramp) when both are available:

(setq cider-prefer-local-resources t)

Auto-Save Clojure Buffers on Load

Normally, CIDER prompts you to save a modified Clojure buffer when you type C-c C-k (cider-load-buffer). You can change this behaviour by adjusting cider-save-file-on-load.

Don't prompt and don't save:

(setq cider-save-file-on-load nil)

Just save without prompting:

(setq cider-save-file-on-load t)

Change the Result Prefix for Interactive Evaluation

Change the result prefix for interactive evaluation (not the REPL prefix). By default the prefix is =>.

(setq cider-eval-result-prefix ";; => ")

To remove the prefix altogether, just set it to the empty string ("").

Use a Local Copy of the JDK API Documentation

If you are targeting the JVM and prefer a local copy of the JDK API documentation over Oracle's official copy (e.g., for JavaSE 8), per nREPL's javadoc-info logic (accurate as of 29 Dec 2014), you can arrange your project to include the root path of the local API doc (i.e., where the index.html is located) to be included on your classpath (i.e., where the doc HTML files can be located by clojure.java.io/resource). For example, for Leiningen, with the local API path being /usr/share/doc/java/api/, put the following line in project.clj:

:dev {:resource-paths ["/usr/share/doc/java/api/"]}

or the following line in $HOME/.lein/profiles.clj:

:user {:resource-paths ["/usr/share/doc/java/api/"]}

More details can be found here.

Use a Local Copy of the Java Source Code

When an exception is thrown, e.g. when eval-ing (. clojure.lang.RT foo), a stack trace pops up. Some places of the stack trace link to Clojure files, others to Java files. By default, you can click the Clojure file links to navigate there. If you configure cider-jdk-src-paths, you can also click the Java file links to navigate there.

On Windows and macOS the JDK source code is bundled with the JDK. On Windows its typical location is C:\Program Files\Java\{jdk-version}\src.zip and on macOS its /Library/Java/JavaVirtualMachines/{jdk-version}/Contents/Home/src.zip.

On Linux distributions usually the source code is distributed as a separate package. Here's how do get the JDK 8 source on Ubuntu:

sudo apt install openjdk-8-source

The zip is installed to /usr/lib/jvm/openjdk-8/src.zip.

You can download Clojure Java source code from here.

Extract both and configure e.g. like so:

(setq cider-jdk-src-paths '("~/java/clojure-1.8.0-sources"
                            "~/java/openjvm-8-src"))

It's possible to use jar or zip files cider-jdk-src-paths, but extracting them is better since you get features like ag or dired-jump.

You can hide all nREPL middleware details from cider-browse-ns* and cider-apropos* commands by customizing the variable cider-filter-regexps. It should be a list of regexps matching the pattern of namespaces you want to filter out.

Its default value is '("^cider.nrepl" "^refactor-nrepl" "^nrepl"), the most commonly used middleware collections/packages.

An important thing to note is that this list of regexps is passed on to the middleware without any pre-processing. So, the regexps have to be in Clojure format (with twice the number of backslashes) and not Emacs Lisp. For example, to achieve the above effect, you could also set cider-filter-regexps to '(".*nrepl").

To customize cider-filter-regexps, you could use the Emacs customize UI, with M-x customize-variable RET cider-filter-regexps.

Or by including a similar snippet along with the other CIDER configuration.

(setq cider-filter-regexps '(".*nrepl"))

Truncate long lines in special buffers

By default contents of CIDER's special buffers such as *cider-test-report* or *cider-doc* are line truncated. You can set cider-special-mode-truncate-lines to nil to make those buffers use word wrapping instead of line truncating.

This variable should be set before loading CIDER (which means before require-ing it or autoloading it).

(setq cider-special-mode-truncate-lines nil)