Out-of-the box CIDER uses the standard Emacs tooling for code completion. When you press TAB or M-TAB you’ll get completion candidates in a dedicated buffer.
There are two things to keep in mind about the standard completion:
Normally TAB only indents, but now it will also do completion if the code is already properly indented.
While the standard Emacs tooling works just fine, we suggest that
CIDER users consider using
company-mode instead. Company
can be used for auto-completion in both source code and REPL buffers.
After installation, you can turn on
or through mode-specific hooks:
(add-hook 'cider-repl-mode-hook #'company-mode) (add-hook 'cider-mode-hook #'company-mode)
company-mode is enabled, it will receive completion information
cider-complete-at-point and requires no additional setup or plugins.
If you’d prefer to trigger completions manually you can add this to your config:
(setq company-idle-delay nil) ; never start completions automatically (global-set-key (kbd "M-TAB") #'company-complete) ; use M-TAB, a.k.a. C-M-i, as manual trigger
To make TAB complete, without losing the ability to manually indent, you can add this to your config:
(global-set-key (kbd "TAB") #'company-indent-or-complete-common)
company-mode will provide completion candidates with the
assumption that whatever you’ve typed so far is a prefix of what
you’re really trying to type. For example, if you type
you’ll only get completion candidates that have
map- as the
beginning of their names. Sometimes, you don’t know the exact prefix
for the item you want to type. In this case, you can get
CIDER-specific "fuzzy completion" by adding:
(add-hook 'cider-repl-mode-hook #'cider-company-enable-fuzzy-completion) (add-hook 'cider-mode-hook #'cider-company-enable-fuzzy-completion)
company-mode will accept certain fuzziness when matching
candidates against the prefix. For example, typing
mi will show you
map-indexed as one of the possible completion candidates and
will complete to
clojure.java.io. Different completion examples are
Completion candidates will be annotated by default with an abbreviation
corresponding to their type, and (contextually) their namespace. The function
used to format the annotation can be configured by
cider-annotate-completion-function. The abbreviations used are configured by
cider-completion-annotations-alist and the context in which their namespace is
included is configured by
Completion annotations can be disabled by setting
Sometimes, the completion fails to recognize new classes that came with
dependencies that were loaded dynamically after the REPL was started (e.g. via
M-x cider-completion-flush-caches (or going through the menu
CIDER Interaction->Misc->Flush completion cache) forces the completion backend
to re-read all classes it can find on the classpath.
You don’t really need to know any of this if you’re using only
The bulk of the code completion logic resides in
cider-nrepl completion middleware. Internally it delegates to
compliment for the Clojure completion and
clj-suitable for the ClojureScript completion.
Starting with nREPL 0.8, there’s also a built-in
completions nREPL op that CIDER will fallback to, in the absence of
cider-nrepl. Its API is similar to that of the
complete op in
cider-nrepl and it can be configured to use different completion functions. The built-in op currently supports only Clojure. See the nREPL docs for more details.
Basically, you’ll get great code completion in the presence of
cider-nrepl and basic completion otherwise.