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Analysis data and tools

Clj-kondo can provide data that was collected during linting, which enables writing tools and linters that are not yet in clj-kondo itself. To get this data, use the following configuration:

{:output {:analysis true}}

When using clj-kondo from the command line, the analysis data will be exported with {:output {:format ...}} set to :json or :edn.


The analysis output consists of a map with:

  • :namespace-definitions, a list of maps with:

    • :filename, :row, :col
    • :name: the name of the namespace


    • several metadata values: :deprecated, :doc, :author, :added, :no-doc (used by codox).
  • :namespace-usages, a list of maps with:

    • :filename, :row, :col
    • :from: the namespace which uses
    • :to: the used namespace
  • :var-definitions, a list of maps with:

    • :filename, :row, :col
    • :ns: the namespace of the var
    • :name: the name of the var


    • :fixed-arities: a set of fixed arities
    • :var-args-min-arity: the minimal number of arguments of a var-args signature
    • several metadata values: :private, :macro, :deprecated, :doc, :added
    • :lang: if definition occurred in a .cljc file, the language in which the definition was done: :clj or :cljs
  • :var-usages, a list of maps with:

    • :filename, :row, :col
    • :name: the name of the used var
    • :from: the namespace from which the var was used
    • :to: the namespace of the used var


    • :arity: if the usage was a function call, the amount of arguments passed
    • :lang: if usage occurred in a .cljc file, the language in which the call was resolved: :clj or :cljs
    • several attributes of the used var: :private, :macro, :fixed-arities, :var-args-min-arity, :deprecated.

Example output after linting this code:

(ns foo
  "This is a useful namespace."
  {:deprecated "1.3"
   :author "Michiel Borkent"
   :no-doc true}
  (:require [clojure.set]))

(defn- f [x]
  (inc x))

(defmacro g
  "No longer used."
  {:added "1.2"
   :deprecated "1.3"}
  [x & xs]
  `(comment ~x ~@xs))
$ clj -m edn /tmp/foo.clj
 [{:filename "/tmp/foo.clj",
   :row 1,
   :col 1,
   :name foo,
   :deprecated "1.3",
   :doc "This is a useful namespace.",
   :no-doc true,
   :author "Michiel Borkent"}],
 [{:filename "/tmp/foo.clj",
   :row 6,
   :col 14,
   :from foo,
   :to clojure.set}],
 [{:filename "/tmp/foo.clj",
   :row 8,
   :col 1,
   :ns foo,
   :name f,
   :private true,
   :fixed-arities #{1}}
  {:added "1.2",
   :ns foo,
   :name g,
   :var-args-min-arity 1,
   :filename "/tmp/foo.clj",
   :macro true,
   :col 1,
   :deprecated "1.3",
   :doc "No longer used.",
   :row 11}],
 [{:filename "/tmp/foo.clj",
   :row 9,
   :col 3,
   :from foo,
   :to clojure.core,
   :name inc,
   :fixed-arities #{1},
   :arity 1}
  {:name defn-,
   :var-args-min-arity 2,
   :filename "/tmp/foo.clj",
   :from foo,
   :macro true,
   :col 1,
   :arity 3,
   :row 8,
   :to clojure.core}
  {:filename "/tmp/foo.clj",
   :row 16,
   :col 5,
   :from foo,
   :to clojure.core,
   :name comment,
   :macro true,
   :var-args-min-arity 0}
  {:name defmacro,
   :var-args-min-arity 2,
   :filename "/tmp/foo.clj",
   :from foo,
   :macro true,
   :col 1,
   :arity 5,
   :row 11,
   :to clojure.core}]}

NOTE: breaking changes may occur as result of feedback in the next few weeks (2019-07-30).

Example tools

These are examples of what you can do with the analysis data that clj-kondo provides as a result of linting your sources.

To run the tools on your system you will need the Clojure CLI tool version or higher and then use this repo as a git dep:

{:deps {clj-kondo/tools {:git/url ""
                         :sha "1ed3b11025b7f3a582e6db099ba10a888fe0fc2c"
                         :deps/root "analysis"}}}

Replace the :sha with the latest SHA of this repo.

You can create an alias for a tool in your ~/.clojure/deps.edn:

 :aliases {:unused-vars
           {:extra-deps {clj-kondo/tools {:git/url ""
                                          :sha "1ed3b11025b7f3a582e6db099ba10a888fe0fc2c"
                                          :deps/root "analysis"}}
            :main-opts ["-m" ""]}

and then call it from anywhere in your system with:

$ clj -A:unused-vars src

Unused vars

$ clj -m src
The following vars are unused:

A planck port of this example is available in the script directory. You can invoke it like this:

script/unused_vars.cljs src

Private vars

A variation on the above tool, which looks at private vars and reports unused private vars or illegally accessed private vars.

Example code:

(ns foo)

(defn- foo [])
(defn- bar []) ;; unused

(ns bar (:require [foo :as f]))

(f/foo) ;; illegal call
$ clj -m /tmp/private.clj
/tmp/private.clj:4:8 warning: foo/bar is private but never used
/tmp/private.clj:8:1 warning: foo/foo is private and cannot be accessed from namespace bar

A planck port of this example is available in the script directory. You can invoke it like this:

script/private_vars.cljs /tmp/private.clj

Namespace graph

This example requires GraphViz. Install with e.g. brew install graphviz.

$ clj -m src

Find var

$ clj -m clj-kondo.core/run! src ../src
clj-kondo.core/run! is defined at ../src/clj_kondo/core.clj:51:7
clj-kondo.core/run! is used at ../src/clj_kondo/core.clj:120:12
clj-kondo.core/run! is used at ../src/clj_kondo/main.clj:81:44
clj-kondo.core/run! is used at src/clj_kondo/tools/find_var_usages.clj:8:29
clj-kondo.core/run! is used at src/clj_kondo/tools/namespace_graph.clj:7:29
clj-kondo.core/run! is used at src/clj_kondo/tools/unused_vars.clj:9:31

Popular vars

$ clj -m 10 ../src
clojure.core/let: 196
clojure.core/defn: 183
clojure.core/when: 115
clojure.core/=: 86
clojure.core/if: 86
clojure.core/recur: 79
clojure.core/assoc: 70
clojure.core/or: 68
clojure.core/->: 68
clojure.core/first: 62

Missing docstrings

$ clj -m ../src
clj-kondo.impl.findings/reg-finding!: missing docstring
clj-kondo.impl.findings/reg-findings!: missing docstring
clj-kondo.impl.namespace/reg-var!: missing docstring
clj-kondo.impl.namespace/reg-var-usage!: missing docstring
clj-kondo.impl.namespace/reg-alias!: missing docstring

Circular dependencies

Example code:

(ns a (:require b c))

(ns b (:require a)) ;; circular dependency

(ns c (:require a)) ;; circular dependency
$ clj -m /tmp/circular.clj
/tmp/circular.clj:3:17: circular dependendy from namespace b to a
/tmp/circular.clj:5:17: circular dependendy from namespace c to a
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