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Flycheck checker for Clojure, using eastwood, core.typed and kibit via cider.

See this blog post for more.


Read these warnings:

  • It is assumed that you are familiar with each of these linters, so please read the their documentation. There, you will find additional warnings.
  • Do not use squiggly-clojure unless your code can be reloaded without side effects, as the linters will be reloading it repeatedly.
  • Eastwood and Kibit are typically run via lein plugins, and use within the REPL vm, as squiggly requires, is not officially supported. (Though in practice it works well.)


flycheck-clojure of course requires cider and flycheck, which it should fetch as dependencdies You can install from Melpa:

M-x package-install flycheck-clojure

but probably the easiest way to ensure proper loading and initializaiton order is via use-package. With the following, simply invoking cider-jack-in will, after cider inititialization, but before actually running, automatically invok flycheck-clojure-setup, which will in turn inject plugin dependencies properly. If you're not careful, cider can end up over-writing the cider-jack-in-dependencies with defaults.

(use-package cider
  :ensure t :defer t
    cider-repl-history-file ".cider-repl-history"  ;; not squiggly-related, but I like it
	nrepl-log-messages t)                          ;; not necessary, but useful for trouble-shooting
  (flycheck-clojure-setup))                        ;; run setup *after* cider load

(use-package flycheck-clojure
  :defer t
  :commands (flycheck-clojure-setup)               ;; autoload
  (eval-after-load 'flycheck
    '(setq flycheck-display-errors-function #'flycheck-pos-tip-error-messages))
  (add-hook 'after-init-hook #'global-flycheck-mode))

(use-package flycheck :ensure t)
(use-package flycheck-pos-tip :ensure t
  :after flycheck)

Alternatively, (1) clone this project and put its elisp/flycheck-clojure/ directory on your path, or (2) download this one file, and install it wherever you like. You can still use use-package if you add

  :pin manual
  :load-path "~/dev/squiggly-clojure/elisp/flycheck-clojure/" ;; or whereever

to the (use-package flycheck-clojure ....) entry.

If you're not using use-package, add to your .emacs:

(eval-after-load 'flycheck '(flycheck-clojure-setup))
(add-hook 'after-init-hook #'global-flycheck-mode)

Installing flycheck-pos-tip as well is strongly recommended, so that linting and type errors don't clash with cider's eldoc information.

M-x package-install flycheck-pos-tip

And add this to your .emacs:

(eval-after-load 'flycheck
  '(setq flycheck-display-errors-function #'flycheck-pos-tip-error-messages))

Alternatively to flycheck-pos-tip you can use flycheck-tip

M-x package-install flycheck-tip

In that case add to your .emacs:

(require 'flycheck-tip)
(flycheck-tip-use-timer 'verbose)

Either way, you should now get the snazzy yellow post-it messages when the cursor is on a squiggly underline.

If you're used to flycheck but not used to cider, you may want

(add-hook 'cider-mode-hook
  (lambda () (setq next-error-function #'flycheck-next-error-function)))

to override the binding to ````cider-jump-to-compilation-error`.

Dependencies in Clojure:

The Clojure code used to invoke the various specific linters is in Clojars:

If you're using a current release of Cider, then this dependency, along with all of Cider's will be injected automatically for you upon cider-jack-in. (Specifically, the dependencies will be added to cider-jack-in-dependencies unless you specifically disable it by setting flycheck-clojure-inject-dependencies-at-jack-in to nil.)

If you want to cider-attach to a running repl, then you'll need to specify the proper dependencies in your profiles.clj or to the project-specific project.clj, as part of the :dependencies vector. E.g.

;; profiles.clj
{:repl {:plugins [[cider/cider-nrepl "A.B.C"] ;; subsitute A.B.C from emacs cider-version variable
        :dependencies [[acyclic/squiggly-clojure "x.y.z" :exclusions [org.clojure/tools.reader]]  ;; substitute x.y.z from above

Note that there may be case differences between emacs' cider-version and the proper cider-nrepl version for the profile; the latter is usually upper-case, e.g. "0.15.0-SNAPSHOT".

squiggly-clojure in turn pulls in the dependencies from its project.clj.

Note that if you want to use core.typed, you will have to add a dependency and make some changes to your ns as described on the github page.


See the sample-project subdirectory for some examples of the configuration methods described below.

From Emacs

Squiggly Clojure comprises three Flycheck checkers, clojure-cider-typed, clojure-cider-kibit and clojure-cider-eastwood. You may exclude one or more of these by including them in the flycheck-disabled-checkers list. This can be done via the Local Variables: block at the end of a .clj file, e.g.

;; Local Variables:
;; flycheck-disabled-checkers: (clojure-cider-kibit)
;; End:

but the following two methods are preferable for such persistent settings.

In project.clj

Add or merge

  :plugins [[lein-environ "1.0.0"]]

and set an :env option map that includes :squiggly , e.g.

{:env {:squiggly {:checkers [:eastwood]
                  :eastwood-exclude-linters [:unlimited-use]}}}

Here, you specify included checkers, as :eastwood, :kibit or :typed. If you set :eastwood-exclude-linters, it will be passed directly to Eastwood as described in its documentation. This configuration will apply to all source files in the project unless overridden by...

Namespace metadata


(ns sample-project.core
  {:squiggly {:checkers [:eastwood :typed]
              :eastwood-exclude-linters [:unlimited-use]}
   :lang :core.typed}
  (:require [clojure.core.typed] :as t)
  (:use [clojure.stacktrace])     ;; warning suppressed by :eastwood-exclude-linters


If set in the namespace metadata, the value of :squiggly fully overrides anything set in the project.clj: no fancy merging is performed.

And note that, if a checker is in flycheck-disabled-checkers, it will never be invoked no matter what you set in Clojure code.

Available options

  :checkers                    [:eastwood :typed :kibit]
  :eastwood-exclude-linters    [] # see Eastwood documentation
  :eastwood-options            {} # See Eastwood documentation

Note that :eastwood-exclude-linters is here for backwards compatibility, and specifying :eastwood-options {:exclude-linter [...]} would override it. If you have really a lot of Eastwood options you want to specify, you can specify :config:files in the :eastwood-options map and really go to town.

Debugging and bug reporting

First, see the warnings above. The general theme is that we depend on three external linters, problems or incompatibilities with any of which might now manifest in emacs.

Maddeningly, the most common way for an incompatibility to manifest is with an uncaught clojure exception that emacs fails to parse, resulting in the cryptic error "Wrong number of arguments: (4 . 4), 0". To debug this, follow the suggestions below, especially the one about pasting the calls to the inter directly in to the REPL buffer so you can see errors, unfiltered by emacs.

You should start by making sure that flycheck-clojure has is in fact being initialized. After you cider-jack-in, the *Messages* buffer will show a message like

[nREPL] Starting server via /home/pnf/bin/lein update-in :dependencies conj \[acyclic/squiggly-clojure\ \"0.1.9-SNAPSHOT\"\  -- update-in :dependencies conj \[nrepl\ \"0.6.0\"\] -- update-in :plugins conj \[refactor-nrepl\ \"2.5.0-SNAPSHOT\"\] -- update-in :plugins conj \[cider/cider-nrepl\ \"0.23.0-SNAPSHOT\"\] -- repl :headless :host localhost

If you don't see acyclic/squiggly-clojure among the :dependencies, then, most likely, will also not see it in cider-jack-in-dependencies. Either flycheck-clojure-setup was never called, or it was called before cider itself was loaded and the alist was overwritten. You should check your emacs configuration, but for now run flycheck-clojure-setup again manually.

Once you're sure that flycheck-clojure is in fact initialized, you can debug further by looking at the messages between cider and the clojure process. These will be in the *nrepl-messages... buffer, but only if you have (setq nrepl-log-messages t); messages are no longer being logged by default.

Among other things, you'll find here the Clojure expressions that were evaluated to initiate the checking, e.g.

  op  "eval"
  session  "5f8764c8-3f2b-4871-9a26-766b4b5af314"
  code  "(do (require 'squiggly-clojure.core) (squiggly-clojure.core/check-tc 'sample-project.core))"
  id  "20"

You can see output from this command by looking for messages with the same id, e.g.

  id  "20"
  ns  "user"
  session  "5f8764c8-3f2b-4871-9a26-766b4b5af314"
  value  "\"[{\\\"line\\\":16,\\\"column\\\":3,\\\"file\\\":\\\"sample_project\\\\/core.clj\\\",\\\"level\\\":\\\"error\\\",\\\"msg\\\":\\\"Static method clojure.lang.Numbers\\\\/inc could not be applied to arguments:\\\\n\\\\n\\\\nDomains:\\\\n\\\\tNumber\\\\n\\\\nArguments:\\\\n\\\\t(clojure.core.typed\\\\/Val \\\\\\\"foo\\\\\\\")\\\\n\\\\nRanges:\\\\n\\\\tNumber\\\\n\\\\n\\\"},{\\\"line\\\":25,\\\"column\\\":13,\\\"file\\\":\\\"sample_project\\\\/core.clj\\\",\\\"level\\\":\\\"error\\\",\\\"msg\\\":\\\"Function range could not be applied to arguments:\\\\n\\\\n\\\\nDomains:\\\\n\\\\tNumber\\\\n\\\\nArguments:\\\\n\\\\tclojure.core.typed\\\\/Any\\\\n\\\\nRanges:\\\\n\\\\t(clojure.core.typed\\\\/ASeq clojure.core.typed\\\\/AnyInteger)\\\\n\\\\n\\\"}]\""

In this case, you can see that type-checking returned a map of results correctly.

If results are correctly returned in the REPL but are not displayed in the Emacs buffer, then there may be an elisp bug to report.

If you see something that looks like an error, you should reproduce it by running the Clojure expression directly from the REPL, e.g. in this case

  (do (require 'squiggly-clojure.core) (squiggly-clojure.core/check-tc 'sample-project.core))

If this returns an error, you should then try replicating outside the REPL using the linter's lein plugin. In the example above, that would be lein-typed, which must be installed separately.

If all linters work propertly outside of the REPL, there may be a reportable bug in the squiggly clojure code, though historically it's usually turned out to be related to dependency conflicts between the linters and the project being linted. Accordingly, when reporting a possible bug, please include the output of lein deps :tree or lein with-profile something deps, where something is probably repl, as appropriate.

If, due to one of these or other problems, flycheck does not receive the proper callbacks, it may be stuck in a state where it will never try to check again. To reset (modulo some memory leaks perhaps) try turning flycheck-mode off and then on.

Developer hints

If you're playing with the squiggly elisp and clojure code, it's cleanest to to start up emacs with the related configurations commented-out in your init.el and profiles.clj. The easiest workflow is then

  1. lein install the package locally
  2. before starting cider, eval flyckeck-clojure.el manually and (flycheck-clojure-setup)
  3. then cider-jack-in, which should now start lein with your local library, with whatever dependencies you might have changed.
  4. subsequently, you can re-eval squiggy-clojure's core.clj as often as you like


  • Deal better with catastrophic failure of a checker. Currently, we silently ignore exceptions.
  • Performance optimizations: throttling and narrowing.


Flycheck checker for Clojure, using eastwood and core.typed.




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