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CIDER is a Clojure Interactive Development Environment that Rocks for Emacs
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README.md

Build Status

CIDER (formerly nrepl.el)

CIDER is Clojure IDE and REPL for Emacs, built on top of nREPL, the Clojure networked REPL server. It's a great alternative to the now deprecated combination of SLIME + swank-clojure.

Installation

Upgrading from nrepl.el

Before installing CIDER make sure you've removed the old nrepl.el package and all packages that depend on it. Use only packages updated to work with CIDER!

You'll also need to adjust your config accordingly, as most settings were renamed in CIDER. Consult the Configuration section of the README for more details.

Via package.el

package.el is the built-in package manager in Emacs 24+. On Emacs 23 you will need to get package.el yourself if you wish to use it.

CIDER is available on both major package.el community maintained repos - Marmalade and MELPA.

If you're not already using one of them, follow their installation instructions: Marmalade, MELPA.

You can install CIDER with the following command:

M-x package-install [RET] cider [RET]

or by adding this bit of Emacs Lisp code to your Emacs initialization file(.emacs or init.el):

(unless (package-installed-p 'cider)
  (package-install 'cider))

If the installation doesn't work try refreshing the package list:

M-x package-refresh-contents [RET]

Keep in mind that MELPA packages are built automatically from the master branch, meaning bugs might creep in there from time to time. Never-the-less, installing from MELPA is the recommended way of obtaining CIDER, as the master branch is normally quite stable and "stable" (tagged) builds are released somewhat infrequently.

Via el-get

el-get is another popular package manager for Emacs. If you're an el-get user just do M-x el-get-install.

Manual

You can install CIDER manually by placing CIDER on your load-path and requireing it. Many people favour the folder ~/.emacs.d/vendor:

(add-to-list 'load-path "~/emacs.d/vendor")
(require 'cider)

Keep in mind that CIDER depends on clojure-mode, dash.el and pkg-info so you'll have to install them as well.

Emacs Prelude

CIDER comes bundled in Emacs Prelude. If you're a Prelude user you can start using it right away.

Emacs Live

CIDER comes bundled in Emacs Live. If you're using Emacs Live you're already good to go.

Configuration

You can certainly use CIDER without configuring it any further, but here are some ways other folks are adjusting their CIDER experience.

  • Enable eldoc in Clojure buffers:
(add-hook 'cider-mode-hook 'cider-turn-on-eldoc-mode)
  • You can hide the *nrepl-connection* and *nrepl-server* buffers from appearing in some buffer switching commands like switch-to-buffer(C-x b) like this:
(setq nrepl-hide-special-buffers t)

When using switch-to-buffer, pressing SPC after the command will make the hidden buffers visible. They'll always be visible in list-buffers (C-x C-b).

  • You can control the TAB key behavior in the REPL via the cider-repl-tab-command variable. While the default command cider-indent-and-complete-symbol should be an adequate choice for most users, it's very easy to switch to another command if you wish to. For instance if you'd like TAB to only indent (maybe because you're used to completing with M-TAB) use the following snippet:
(setq cider-repl-tab-command 'indent-for-tab-command)
  • Prevent the auto-display of the REPL buffer in a separate window after connection is established:
(setq cider-repl-pop-to-buffer-on-connect nil)
  • Stop the error buffer from popping up while working in buffers other than the REPL:
(setq cider-popup-stacktraces nil)
  • Enable error buffer popping also in the REPL:
(setq cider-repl-popup-stacktraces t)
  • To auto-select the error buffer when it's displayed:
(setq cider-auto-select-error-buffer t)
  • The REPL buffer name takes the format *cider project-name*. Change the separator from space to something else by overriding nrepl-buffer-name-separator.
(setq nrepl-buffer-name-separator "-")
  • The REPL buffer name can also display the port on which the nREPL server is running. Buffer name will look like cider project-name:port.
(setq nrepl-buffer-name-show-port t)
  • Make C-c C-z switch to the CIDER REPL buffer in the current window:
(setq cider-repl-display-in-current-window t)
  • Enabling CamelCase support for editing commands(like forward-word, backward-word, etc) in the REPL is quite useful since we often have to deal with Java class and method names. The built-in Emacs minor mode subword-mode provides such functionality:
(add-hook 'cider-repl-mode-hook 'subword-mode)
  • The use of paredit when editing Clojure (or any other Lisp) code is highly recommended. You're probably using it already in your clojure-mode buffers (if you're not you probably should). You might also want to enable paredit in the REPL buffer as well:
(add-hook 'cider-repl-mode-hook 'paredit-mode)
  • smartparens is an excellent alternative to paredit. Many Clojure hackers have adopted it recently and you might want to give it a try as well. To enable smartparens in the REPL buffer use the following code:
(add-hook 'cider-repl-mode-hook 'smartparens-strict-mode)
  • RainbowDelimiters is a minor mode which highlights parentheses, brackets, and braces according to their depth. Each successive level is highlighted in a different color. This makes it easy to spot matching delimiters, orient yourself in the code, and tell which statements are at a given depth. Assuming you've already installed RainbowDelimiters you can enable it in the REPL like this:
(add-hook 'cider-repl-mode-hook 'rainbow-delimiters-mode)
  • ac-nrepl provides completion source for the popular Emacs interactive auto-completion framework auto-complete. Where nrepl provides it, pop-up documentation for completed symbols will be displayed.

Basic Usage

The only requirement to use CIDER is to have a nREPL server to which it may connect. Many Clojurians favour the use of the Leiningen tool to start a nREPL server, but the use of Leiningen is not a prerequisite to use CIDER (but it's required if you want to use the cider-jack-in command).

Setting up a Leiningen project (optional)

Leiningen is the de facto standard build/project management tool for Clojure. It has a similar scope to the Maven build tool favoured by Java developers (Leiningen actually reuses many things from the Maven ecosystem).

CIDER features a command called cider-jack-in that will start an nREPL server for a particular Leiningen project and connect to it automatically. This functionality depends on Leiningen 2. Older versions are not supported. Follow the installation instructions on Leiningen's web site to get it up and running and afterwards create a project like this:

$ lein new demo

The two main ways to obtain an nREPL connection are discussed in the following sections of the manual.

Launch a nREPL server and client from Emacs

Simply open in Emacs a file belonging to your lein project (like foo.clj) and type M-x cider-jack-in. This will start a nREPL with all the deps loaded in, plus an CIDER client connected to it.

Alternative you can use C-u M-x cider-jack-in to specify the name of a lein project, without having to visit any file in it.

Connect to a running nREPL server

You can go to your project's dir in a terminal and type there (assuming you're using Leiningen that is):

$ lein repl

Alternatively you can start nREPL either manually or by the facilities provided by your project build tool (Maven, etc).

After you get your nREPL server running go back to Emacs. Typing there M-x cider will allow you to connect to the running nREPL server.

Using the cider minor mode

CIDER comes with a handy minor mode called cider-mode (complementing clojure-mode) that allows you to evaluate code in your Clojure source files and load it directly in the REPL. A list of all available commands is available in the CIDER menu and in the following section of this manual.

Pretty printing in the REPL

Make the REPL always pretty-print the results of your commands. Note that this will not work correctly with forms such as (def a 1) (def b2) and it expects clojure.pprint to have been required already (the default in more recent versions of Clojure):

M-x cider-toggle-pretty-printing

Keyboard shortcuts

  • M-x cider-jack-in: Launch an nREPL server and a repl client. Prompts for a project root if given a prefix argument.
  • M-x cider: Connect to an already-running nREPL server.

While you're in clojure-mode, cider-jack-in is bound for convenience to C-c M-j and cider is bound to C-c M-c.

Clojure buffer commands:

Keyboard shortcut Description
C-x C-e Evaluate the form preceding point and display the result in the echo area. If invoked with a prefix argument, insert the result into the current buffer.
C-c C-p Evaluate the form preceding point and display the result in a popup buffer.
C-M-x C-c C-c Evaluate the top level form under point and display the result in the echo area. If invoked with a prefix argument, insert the result into the current buffer.
C-c C-r Evaluate the region and display the result in the echo area.
C-c C-b Interrupt any pending evaluations.
C-c C-m Invoke macroexpand-1 on the form at point and display the result in a macroexpansion buffer. If invoked with a prefix argument, macroexpand is used instead of macroexpand-1.
C-c M-m Invoke clojure.walk/macroexpand-all on the form at point and display the result in a macroexpansion buffer.
C-c C-n Eval the ns form.
C-c M-n Switch the namespace of the repl buffer to the namespace of the current buffer.
C-c C-z Select the REPL buffer. With a prefix argument - changes the namespace of the REPL buffer to the one of the currently visited source file.
C-u C-u C-c C-z Select the REPL buffer based on a user prompt for a directory.
C-c M-d Display current REPL connection details, including project directory name, buffer namespace, host and port.
C-c M-r Rotate and display the current REPL connection.
C-c M-o Clear the entire REPL buffer, leaving only a prompt. Useful if you're running the REPL buffer in a side by side buffer.
C-c C-k Load the current buffer.
C-c C-l Load a file.
C-c C-d Display doc string for the symbol at point. If invoked with a prefix argument, or no symbol is found at point, prompt for a symbol.
C-c C-s Display the source for the symbol at point. If invoked with a prefix argument, or no symbol is found at point, prompt for a symbol.
C-c C-j Display JavaDoc (in your default browser) for the symbol at point. If invoked with a prefix argument, or no symbol is found at point, prompt for a symbol.
M-. Jump to the definition of a symbol. If invoked with a prefix argument, or no symbol is found at point, prompt for a symbol.
M-, Return to your pre-jump location.
M-TAB Complete the symbol at point. (For auto-complete integration, see ac-nrepl)

REPL buffer commands:

Keyboard shortcut Description
RET Evaluate the current input in Clojure if it is complete. If incomplete, open a new line and indent. If invoked with a prefix argument is given then the input is evaluated without checking for completeness.
C-RET Close any unmatched parenthesis and then evaluate the current input in Clojure.
C-j Open a new line and indent.
C-c M-o Clear the entire REPL buffer, leaving only a prompt.
C-c C-o Remove the output of the previous evaluation from the REPL buffer.
C-c C-u Kill all text from the prompt to the current point.
C-c C-b C-c C-c Interrupt any pending evaluations.
C-up C-down Goto to previous/next input in history.
M-p M-n Search the previous/next item in history using the current input as search pattern. If M-p/M-n is typed two times in a row, the second invocation uses the same search pattern (even if the current input has changed).
M-s M-r Search forward/reverse through command history with regex.
C-c C-n C-c C-p Move between the current and previous prompts in the REPL buffer. Pressing RET on a line with old input copies that line to the newest prompt.
TAB Complete symbol at point.
C-c C-d Display doc string for the symbol at point. If invoked with a prefix argument, or no symbol is found at point, prompt for a symbol
C-c C-j Display JavaDoc (in your default browser) for the symbol at point. If invoked with a prefix argument, or no symbol is found at point, prompt for a symbol.
C-c C-z Select the last Clojure buffer. C-u C-c C-z will switch the Clojure buffer to the namespace in the current buffer.
C-u C-u C-c C-z Select the Clojure buffer based on a user prompt for a directory.
C-c M-d Display current REPL connection details, including project directory name, buffer namespace, host and port.
C-c M-r Rotate and display the current REPL connection.

Macroexpansion buffer commands:

Keyboard shortcut Description
C-c C-m Invoke macroexpand-1 on the form at point and replace the original form with its expansion. If invoked with a prefix argument, macroexpand is used instead of macroexpand-1.
C-c M-m Invoke clojure.walk/macroexpand-all on the form at point and replace the original form with its expansion.
g The prior macroexpansion is performed again and the current contents of the macroexpansion buffer are replaced with the new expansion.
C-/ C-x u Undo the last inplace expansion performed in the macroexpansion buffer.

Managing multiple sessions

You can connect to multiple nREPL servers and use M-x cider-jack-in multiple times. To close a single nREPL session, use M-x nrepl-close. M-x nrepl-quit closes all sessions.

CIDER commands in a Clojure buffer use the default connection. To make a connection default, switch to it's repl buffer and use M-x nrepl-make-repl-connection-default.

To switch to the relevant REPL buffer based on the Clojure namespace in the current buffer, use: C-c C-z.

You can display the current nREPL connection using C-c M-d and rotate through available connections using C-c M-r.

Requirements

Changelog

An extensive changelog is available here.

Extensions

There are a couple of CIDER extensions that add some extra functionality to it:

Team

Contributing

Bug reports and suggestions for improvements are always welcome. GitHub pull requests are even better! :-)

Running the tests in batch mode

Install cask if you haven't already, then:

$ cd /path/to/cider
$ cask

Run all tests with:

$ make test

License

Copyright © 2012-2013 Tim King, Phil Hagelberg, Bozhidar Batsov, Hugo Duncan, Steve Purcell and contributors.

Distributed under the GNU General Public License, version 3

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