CIDER (formerly nrepl.el) is the 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
- Configuration
- Basic Usage
- Keyboard shortcuts
- Requirements
- Caveats
- Changelog
- Team
- Contributing
- License
You'll need to have Emacs installed (preferably the latest stable release). If you're new to Emacs you might want to read this tutorial, dedicated to setting up Emacs for Clojure development, first.
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.
package.el is the built-in package manager in Emacs.
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.
el-get is another popular package manager for Emacs. If you're an el-get user just do M-x el-get-install.
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.
CIDER comes bundled in
Emacs Prelude. If you're a
Prelude user you can start using it right away.
CIDER comes bundled in
Emacs Live. If you're using
Emacs Live you're already good to go.
Much of CIDER's functionality depends on the presence of CIDER's own nREPL middleware.
Use the convenient plugin for defaults, either in your project's
project.clj file or in the :user profile in ~/.lein/profiles.clj.
:plugins [[cider/cider-nrepl "0.6.0"]]You can certainly use CIDER without configuring it any further,
but here are some ways other folks are adjusting their CIDER
experience.
- Enable
eldocin 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 likeswitch-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-commandvariable. While the default commandcider-repl-indent-and-complete-symbolshould 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)- If using the
wrap-stacktracemiddleware fromcider-nrepl, error buffer stacktraces may be filtered by default. Valid filter types includejava,clj,repl,tooling, anddup. Setting this tonilwill show all stacktrace frames.
(setq cider-stacktrace-default-filters '(tooling dup))- Error messages may be wrapped for readability. If this value is nil, messages
will not be wrapped; if it is truthy but non-numeric, the default
fill-columnwill be used.
(setq cider-stacktrace-fill-column 80)- The REPL buffer name has the format
*cider-repl project-name*. Change the separator from space to something else by overridingnrepl-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-repl 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)- Limit the number of items of each collection the printer will print to 100:
(setq cider-repl-print-length 100) ; the default is nil, no limit- Prevent C-c C-k from prompting to save the file corresponding to the buffer being loaded, if it's modified:
(setq cider-prompt-save-file-on-load nil)- Change the result prefix for REPL evaluation (by default there's no prefix):
(set cider-repl-result-prefix ";; => ")And here's the result of that change:
user> (+ 1 2)
;; => 3
- Change the result prefix for interactive evaluation (by default it's
=>):
(set cider-interactive-eval-result-prefix ";; => ")To remove the prefix altogether just set it to an empty string("").
- Normally code you input in the REPL is font-locked with
cider-repl-input-face(after you pressRET) and results are font-locked withcider-repl-result-face. If you want them to be font-locked as inclojure-modeuse the following:
(setq cider-repl-use-clojure-font-lock t)- You can control the C-c C-z key behavior of switching to the REPL buffer
with the
cider-switch-to-repl-commandvariable. While the default commandcider-switch-to-relevant-repl-buffershould be an adequate choice for most users,cider-switch-to-current-repl-bufferoffers a simpler alternative where CIDER will not attempt to match the correct REPL buffer based on underlying project directories:
(setq cider-switch-to-repl-command 'cider-switch-to-current-repl-buffer)- You can configure known endpoints used by the cider command offered via a completing read. This is useful if you have a list of common host/ports you want to establish remote nREPL connections to. Using an optional label is helpful for identifying each host.
(setq cider-known-endpoints '(("host-a" "10.10.10.1" "7888") ("host-b" "7888")))- To make the REPL history wrap around when its end is reached:
(setq cider-repl-wrap-history t)- To adjust the maximum number of items kept in the REPL history:
(setq cider-repl-history-size 1000) ; the default is 500- To store the REPL history in a file:
(setq cider-repl-history-file "path/to/file")Note that the history is written to the file when you kill the REPL
buffer (which includes invoking cider-quit) or you quit Emacs.
Out-of-the box CIDER uses the standard completing-read Emacs mechanism. While it's not
fancy it certainly gets the job done (just press TAB). There are, however, ways to improve
upon the standard completion if you wish to.
icomplete is bundled with Emacs and enhances the default minubuffer completion:
(require 'icomplete)ido is also bundled with Emacs and offers more features than icomplete.
If you are using ido, be sure to use both ido-everywhere
and ido-ubiquitous.
You might also want to install ido-flex.
- Enabling
CamelCasesupport for editing commands(likeforward-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 modesubword-modeprovides 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-modebuffers (if you're not you probably should). You might also want to enablepareditin 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
smartparensin 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)-
company-mode provides in-buffer completion framework. When its
company-capfback-end is enabled, it will retrieve completion information fromcider-complete-at-point, requiring no additional setup. On Emacs 24.4 and newercompany-capfis enabled out of the box.CIDERusers are advised to usecompany-modeinstead ofauto-complete-modefor optimal results. -
ac-nrepl provides completion source for the popular Emacs interactive auto-completion framework auto-complete. Where CIDER provides it, pop-up documentation for completed symbols will be displayed.
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).
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.
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.
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-connect will allow you to connect to the running nREPL server.
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.
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-repl-toggle-pretty-printing
Accidentally printing large objects can be detrimental to your
productivity. Clojure provides the *print-length* var which, if set,
controls how many items of each collection the printer will print. You
can supply a default value for REPL sessions by setting the
cider-repl-print-length variable to an integer value. The
enforcement of this limit can then be toggled using:
M-x cider-repl-toggle-print-length-limiting
- 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-connect is bound to C-c
M-c.
| Keyboard shortcut | Description |
|---|---|
| C-x C-e C-c 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-w | Evaluate the form preceding point and replace it with its result. |
| C-c M-e | Evaluate the form preceding point and output it result to the REPL buffer. If invoked with a prefix argument, takes you to the REPL buffer after being invoked. |
| C-c M-p | Load the form preceding point in the REPL buffer. |
| C-c C-p | Evaluate the form preceding point and pretty-print the result in a popup buffer. |
| C-c C-f | Evaluate the top level form under point and pretty-print 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 | Switch to the relevant REPL buffer. Use a prefix argument to change the namespace of the REPL buffer to match the currently visited source file. |
| C-u C-u C-c C-z | Switch to the REPL buffer based on a user prompt for a directory. |
| C-c M-d | Display default REPL connection details, including project directory name, buffer namespace, host and port. |
| C-c M-r | Rotate and display the default nREPL 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. |
| C-c M-i | Inspect expression. Will act on expression at point if present. |
| C-c M-t | Toggle var tracing. |
| 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. |
| 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 | Switch to the previous Clojure buffer. This complements C-c C-z used in cider-mode. |
| C-c M-f | Select a function from the current namespace and insert into the REPL buffer. |
| C-c M-i | Inspect expression. Will act on expression at point if present. |
| C-c M-n | Select a namespace and switch to it. |
| C-c M-t | Toggle var tracing. |
In the REPL you can also use "shortcut commands" by pressing , at the beginning of a REPL line. You'll be presented with a list of commands you can quickly run (like quitting, displaying some info, clearing the REPL, etc). The character used to trigger the shortcuts is configurable via cider-repl-shortcut-dispatch-char. Here's how you can change it to ::
(setq cider-repl-shortcut-dispatch-char ?\:)| 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. |
| Keyboard shortcut | Description |
|---|---|
| Tab and Shift-Tab | navigate inspectable sub-objects |
| Return | inspect sub-objects |
| l | pop to the parent object |
| g | refresh the inspector (e.g. if viewing an atom/ref/agent) |
| Keyboard shortcut | Description |
|---|---|
| Return and M-. | navigate to the source location (if available) for the stacktrace frame |
| j | toggle display of java frames |
| c | toggle display of clj frames |
| r | toggle display of repl frames |
| t | toggle display of tooling frames (e.g. compiler, nREPL middleware) |
| d | toggle display of duplicate frames |
| a | toggle display of all frames |
You can connect to multiple nREPL servers using M-x cider-jack-in multiple times. To close the current nREPL connection, use M-x nrepl-close. M-x cider-quit closes all connections.
CIDER maintains a list of nREPL connections and a single 'default' connection. When you execute CIDER commands in a Clojure editing buffer such as to compile a namespace, these commands are executed against the default connection.
You can display the default nREPL connection using C-c M-d and rotate the default connection using C-c M-r. Another option for setting the default connection is to execute the command M-x nrepl-make-repl-connection-default in the appropriate REPL buffer.
To switch to the relevant REPL buffer based on the Clojure namespace in the current Clojure buffer, use: C-c C-z. You can then use the same key combination to switch back to the Clojure buffer you came from.
The single prefix C-u C-c C-z, will switch you to the relevant REPL buffer and set the namespace in that buffer based on namespace in the current Clojure buffer.
To explicitly choose the REPL buffer that C-c C-z uses
based on project directory, use a double prefix C-u C-u C-c
C-z. This assumes you have cider-switch-to-relevant-repl
mapped to the var cider-switch-to-repl-command which is the default
configuration.
To change the designation used for CIDER buffers use M-x
cider-change-buffers-designation. This changes the CIDER REPL
buffer, nREPL connection buffer and nREPL server buffer. For example
using cider-change-buffers-designation with the string "foo" would
change *cider-repl localhost* to *cider-repl foo*.
ClojureScript completion is provided by the
cider-nrepl 'complete'
implementation middleware which relies on
piggieback. Include it in
your project middlewares and call (cemerick.piggieback/cljs-repl) or
another method to start up the cljs REPL.
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.
The powershell inferior shell mode truncates cider repl output when loaded. As a workaround remove
(require 'powershell)from your Emacs config.
An extensive changelog is available here.
- Bozhidar Batsov (maintainer)
- Tim King (original author)
- Phil Hagelberg
- Hugo Duncan
- Steve Purcell
CIDER's logo was created by @ndr-qef. You can find the logo in various formats here.
The logo is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.
For questions, suggestions and support refer to our official mailing list
or the Freenode channel #clojure-emacs.
Please, don't report issues there, as this makes them harder to track.
Report issues and suggest features and improvements on the GitHub issue tracker. Don't ask questions on the issue tracker - the mailing list is the place for questions.
Patches under any form are always welcome! GitHub pull requests are even better! :-)
Before submitting a patch or a pull request make sure all tests are passing and that your patch is in line with the contribution guidelines.
Consider improving and extending the community wiki.
I'm also accepting financial contributions via gittip.
Install cask if you haven't already, then:
$ cd /path/to/cider
$ cask
Run all tests with:
$ make test
Copyright © 2012-2014 Tim King, Phil Hagelberg, Bozhidar Batsov, Hugo Duncan, Steve Purcell and contributors.
Distributed under the GNU General Public License, version 3