CIDER comes with a powerful REPL that complements the interactive
development functionality in cider-mode
. Using the CIDER REPL you
can experiment with your running program, test functions, or just
explore a new library you're interested in using. The CIDER REPL offers a number of advanced features:
- auto-completion
- font-locking (the same as in
clojure-mode
) - quick access to many CIDER commands (e.g. definition and documentation lookup, tracing, etc)
- (optional) pretty-printing of evaluation results
- eldoc support
- highly customizable REPL prompt
Here's a list of the keybindings that are available in CIDER's REPL:
Keyboard shortcut | Description |
---|---|
RET | Evaluate the current input in Clojure if it is complete. If incomplete, open a new line and indent. If the current input is a blank string (containing only whitespace including newlines) then clear the input without evaluating and print a fresh prompt. 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 C-o | Remove the output of the previous evaluation from the REPL buffer. With a prefix argument it will clear the entire REPL buffer, leaving only a prompt. |
C-c M-o | Switch between the Clojure and ClojureScript REPLs for the current project. |
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 |
Go to 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 d C-c C-d 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-d j C-c C-d 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-d r C-c C-d C-r |
Lookup symbol in Grimoire. |
C-c C-d a C-c C-d C-a |
Apropos search for functions/vars. |
C-c C-d f C-c C-d C-f |
Apropos search for documentation. |
C-c C-z | Switch to the previous Clojure buffer. This complements C-c C-z used in cider-mode. |
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 C-. | Jump to some namespace on the classpath. |
C-c M-t v | Toggle var tracing. |
C-c M-t n | Toggle namespace tracing. |
C-c C-t t C-c C-t C-t |
Run test at point. |
C-c C-t g C-c C-t C-g |
Re-run the last test you ran. |
C-c C-t n C-c C-t C-n |
Run tests for current namespace. |
C-c C-t l C-c C-t C-l |
Run tests for all loaded namespaces. |
C-c C-t p C-c C-t C-p |
Run tests for all project namespaces. This loads the additional namespaces. |
C-c C-t r C-c C-t C-r |
Re-run test failures/errors. |
C-c C-t b C-c C-t C-b |
Show the test report buffer. |
C-c C-q | Quit the current nREPL connection. With a prefix argument it will quit all connections. |
There's no need to memorize this list. In any REPL buffer you'll have a REPL
menu available, which lists all the most important commands and their
keybindings. You can also invoke C-h f RET cider-repl-mode
to get a list of the
keybindings for cider-repl-mode
.
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 ?\;)
REPL Configuration
Behavior on connect
Normally, when you first establish a REPL connection, the REPL buffer is auto-displayed in a separate window. You can suppress this behaviour like this:
(setq cider-repl-pop-to-buffer-on-connect nil)
If you want the REPL buffer to be auto-displayed, but don't want it to be focused, use this:
(setq cider-repl-pop-to-buffer-on-connect 'display-only)
Behavior on switch
By default C-c C-z will display the REPL buffer in a different window. You can make C-c C-z switch to the CIDER REPL buffer in the current window:
(setq cider-repl-display-in-current-window t)
Eldoc
Eldoc displays function signatures in the minibuffer as you're typing.
It's extremely useful! Enable eldoc
in REPL buffers like this:
(add-hook 'cider-repl-mode-hook #'eldoc-mode)
Customizing the REPL prompt
You can customize the REPL buffer prompt by setting
cider-repl-prompt-function
to a function that takes one
argument, a namespace name. For convenience, CIDER provides three
functions that implement common formats:
cider-repl-prompt-lastname
:
ssl>
cider-repl-prompt-abbreviated
:
l.c.ssl>
cider-repl-prompt-default
:
leiningen.core.ssl>
By default, CIDER uses cider-repl-prompt-default
.
You may, of course, write your own function. For example, in leiningen
there
are two namespaces with similar names - leiningen.classpath
and
leiningen.core.classpath
. To make them easily recognizable you can either
use the default value or you can opt to show only two segments of the
namespace and still be able to know which is the REPL's current
namespace. Here is an example function that will do exactly that:
(defun cider-repl-prompt-show-two (namespace)
"Return a prompt string with the last 2 segments of NAMESPACE."
(let ((names (reverse (subseq (reverse (split-string namespace "\\.")) 0 2))))
(concat (car names) "." (cadr names) "> ")))
TAB Completion
You can control the TAB key behavior in the REPL using the
cider-repl-tab-command
variable. While the default command
cider-repl-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:
(setq cider-repl-tab-command #'indent-for-tab-command)
Auto-scrolling the REPL on Output
By default, if the REPL buffer contains more lines than the size of the (Emacs) window, the buffer is automatically re-centered upon completion of evaluating an expression, so that the bottom line of output is on the bottom line of the window.
The default has the nice advantage that you always see as much as you
can from your previous REPL interactions, but can be pretty annoying
if you're a heavy user of C-l
(M-x recenter-top-bottom
), as even
if you're at the top of the REPL buffer the next output will scroll it all
the way down.
If you don't like this re-centering you can disable it like this:
(setq cider-repl-scroll-on-output nil)
Result Prefix
You can change the string used to prefix REPL results:
(setq cider-repl-result-prefix ";; => ")
Which then results in the following REPL output:
user> (+ 1 2)
;; => 3
By default, REPL results have no prefix.
Customize the REPL Buffer's Name
The REPL buffer name has the format *cider-repl project-name*
. You
can change the separator from a space character to something else by
setting 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.
The buffer name will look like *cider-repl project-name:port*
.
(setq nrepl-buffer-name-show-port t)
Font-locking
Normally, code in the REPL is font-locked the same way as in
clojure-mode
. Before CIDER 0.10, by default, REPL input was
font-locked with cider-repl-input-face
(after pressing
Return) and results were font-locked with
cider-repl-result-face
. If you want to restore the old behaviour
use:
(setq cider-repl-use-clojure-font-lock nil)
Pretty printing in the REPL
You can make the REPL always pretty-print the results of your evaluations using M-x cider-repl-toggle-pretty-printing.
To make this behavior the default:
(setq cider-repl-use-pretty-printing t)
Displaying images in the REPL
Starting with CIDER 0.17 (AndalucĂa) expressions that evaluate to images will be rendered as images in the REPL. You can disable this behavior if you don't like it.
(setq cider-repl-use-content-types nil)
Alternatively, you can toggle this behaviour on and off using M-x cider-repl-toggle-content-types.
Currently, the feature doesn't work well with pretty-printing in the REPL, so we don't advise you to enable both features at the same time.
Limiting printed output in the REPL
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 via the repl-options
section of your Leiningen project's configuration.
:repl-options {:init (set! *print-length* 50)}
You can also set cider-repl-print-length
to an appropriate value (it
defaults to 100). If both *print-length
and
cider-repl-print-length
are set, CIDER's setting will take precedence
over the value set through Leiningen.
The preceeding discussion also applies to Clojure's *print-level*
variable. The corresponding CIDER variable is
cider-repl-print-level
, set to nil
by default.
Customizing the initial REPL namespace
Normally, the CIDER REPL will start in the user
namespace. You can
supply an initial namespace for REPL sessions in the repl-options
section of your Leiningen project configuration:
:repl-options {:init-ns 'my-ns}
Customizing newline interaction
Ordinarily, Return immediate sends a form for evaluation. If you want to insert a newline into the REPL buffer as you're editing, you can do so using C-j. If you are entering a lot of longer forms that span multiple lines, it may be more convenient to change the keybindings:
(define-key cider-repl-mode-map (kbd "RET") #'cider-repl-newline-and-indent)
(define-key cider-repl-mode-map (kbd "C-<return>") #'cider-repl-return)
This will make Return insert a newline into the REPL buffer
and C-
REPL history
- To make the REPL history wrap around when CIDER reaches the end:
(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 CIDER writes the history to the file when you kill the REPL
buffer, which includes invoking cider-quit
, or when you quit Emacs.
REPL history browser
You can browse your REPL input history with the command M-x
cider-repl-history
. This command is bound to C-c M-p
in cider-repl-mode
buffers and is also available via the
history
shortcut.
The history is displayed in reverse order, with the most recent input at the top of the buffer, and the oldest input at the bottom. You can scroll through the history, and when you find the history item you were looking for, you can insert it from the history buffer into your REPL buffer.
Mode
The history buffer has its own major mode,
cider-repl-history-mode
. This is derived from clojure-mode
, so you
get fontification in the history buffer. This mode supports the
expected defcustom hook variable, cider-repl-history-hook
.
Insertion
Where you use the history buffer to insert text into the REPL buffer, the exact behavior depends on the location of the cursor in the buffer prior to the insertion.
Typically, when you're actively using the REPL, your cursor will be at
the end of the REPL buffer (point-max
). In this case, the text is
inserted at the end of the buffer and the point advances to the end of
the inserted text (as if point was pushed by along by the text as it
was inserted).
In the unusual case where you invoke the history browser when your
cursor is not at the end of the REPL buffer, the inserted text will
still be inserted at the end of the buffer (point-max
), but the
point is not modified.
CIDER inserts the text without a final newline, allowing you to edit it. When you are ready, hit Return to have it evaluated by the REPL.
Quitting
If you select an input, the text will be inserted into the REPL buffer
and the history buffer will automatically quit. If you decide you want
to quit without inserting any text at all, you can explicitly quit by
running cider-repl-history-quit
(see keyboard shortcuts). Because
of the initialization and cleanup that is done when using the history
buffer, it is better to quit properly rather than just switch away
from the history buffer.
When you quit the history buffer, CIDER can restore the buffer and
window configuration in a few different ways. The behavior is
controlled by cider-repl-history-quit-action
, which can be assigned
one of several values:
quit-window
restores the window configuration to what it was before. This is the default.delete-and-restore
restores the window configuration to what it was before, and kills the*cider-repl-history*
buffer.kill-and-delete-window
kills the*cider-repl-history*
buffer, and deletes the window.bury-buffer
simply buries the*cider-repl-history*
buffer, but keeps the window.bury-and-delete-window
buries the buffer, and deletes the window if there is more than one window.- any other value is interpreted as the name of a function to call
Filtering
By invoking cider-repl-history-occur
from the history buffer, you
will be prompted for a regular expression. The history buffer will be
filtered to only those inputs that match the regexp.
Preview and Highlight
When cider-repl-history-show-preview
is non-nil, CIDER displays an [overlay
]
(https://www.gnu.org/software/emacs/manual/html_node/elisp/Overlays.html)
of the currently selected history entry, in the REPL buffer.
If you do not properly quit from browsing the history (i.e., if you
just C-x b away from the buffer), you may be left with an
unwanted overlay in your REPL buffer. If this happens, you can clean
it up with M-x cider-repl-history-clear-preview
.
By default, cider-repl-history-show-preview
is nil (disabled).
There is a related feature to highlight the entry once it is actually
inserted into the REPL buffer, controlled by the variable
cider-repl-history-highlight-inserted-item
, which can be set to the
following values:
solid
highlights the inserted text for a fixed period of time.pulse
causes the highlighting to fade out gradually.t
selects the default highlighting style, which is currentlypulse
.nil
disables highlighting. This is the default value forcider-repl-history-highlight-inserted-item
.
When cider-repl-history-highlight-inserted-item
is non-nil, you
can customize the face used for the inserted text with the variable
cider-repl-history-inserted-item-face
.
Additional Customization
There are quite a few customizations available, in addition to the ones already mentioned.
cider-repl-history-display-duplicates
- when set tonil
, will not display any duplicate entries in the history buffer. Default ist
.cider-repl-history-display-duplicate-highest
- when not displaying duplicates, this controls where in the history the one instance of the duplicated text is displayed. Whent
, it displays the entry in the highest position applicable; whennil
, it displays it in the lowest position.cider-repl-history-display-style
- the history entries will often be more than one line. The package gives you two options for displaying the entries:separated
- a separator string is inserted between entries; entries may span multiple lines. This is the default.one-line
- any newlines are replaced with literal\n
strings, and therefore no separator is necessary. Each\n
becomes a proper newline when the text is inserted into the REPL.
cider-repl-history-separator
- whencider-repl-history-display-style
isseparated
, this gives the text to use as the separator. The default is a series of ten semicolons, which is, of course, a comment in Clojure. The separator could be anything, but it may screw up the fontification if you make it something weird.cider-repl-history-separator-face
- specifies the face for the separator.cider-repl-history-maximum-display-length
- when nil (the default), all history items are displayed in full. If you prefer to have long items abbreviated, you can set this variable to an integer, and each item will be limited to that many characters. (This variable does not affect the number of items displayed, only the maximum length of each item.)cider-repl-history-recenter
- when non-nil, always keep the current entry at the top of the history window. Default is nil.cider-repl-history-resize-window
- whether to resize the history window to fit its contents. Value is either t, meaning yes, or a cons pair of integers, (MAXIMUM . MINIMUM) for the size of the window. MAXIMUM defaults to the window size chosen bypop-to-buffer
; MINIMUM defaults towindow-min-height
.cider-repl-history-highlight-current-entry
- if non-nil, highlight the currently selected entry in the history buffer. Default is nil.cider-repl-history-current-entry-face
- specifies the face for the history-entry highlight.cider-repl-history-text-properties
- when set tot
, maintains Emacs text properties on the entry. Default isnil
.
Key Bindings
There are a number of important keybindings in history buffers.
Keyboard shortcut | Description |
---|---|
n | Go to next (lower, older) item in the history. |
p | Go to previous (higher, more recent) item in the history. |
RET or SPC | Insert history item (at point) at the end of the REPL buffer, and quit. |
l (lower-case L) | Filter the command history (see Filtering, above). |
s | Regexp search forward. |
r | Regexp search backward. |
q | Quit (and take quit action). |
U | Undo in the REPL buffer. |