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Configuration in MegaLinter

Variable Description Default value
CLOJURE_CLJ_KONDO_ARGUMENTS User custom arguments to add in linter CLI call
Ex: -s --foo "bar"
CLOJURE_CLJ_KONDO_FILTER_REGEX_INCLUDE Custom regex including filter
Ex: (src\|lib)
Include every file
CLOJURE_CLJ_KONDO_FILTER_REGEX_EXCLUDE Custom regex excluding filter
Ex: (test\|examples)
Exclude no file
CLOJURE_CLJ_KONDO_CLI_LINT_MODE Override default CLI lint mode
- file: Calls the linter for each file
- list_of_files: Call the linter with the list of files as argument
- project: Call the linter from the root of the project
CLOJURE_CLJ_KONDO_FILE_EXTENSIONS Allowed file extensions. "*" matches any extension, "" matches empty extension. Empty list excludes all files
Ex: [".py", ""]
[".clj", ".cljs", ".cljc", ".edn"]
CLOJURE_CLJ_KONDO_FILE_NAMES_REGEX File name regex filters. Regular expression list for filtering files by their base names using regex full match. Empty list includes all files
Ex: ["Dockerfile(-.+)?", "Jenkinsfile"]
Include every file
CLOJURE_CLJ_KONDO_PRE_COMMANDS List of bash commands to run before the linter None
CLOJURE_CLJ_KONDO_POST_COMMANDS List of bash commands to run after the linter None
CLOJURE_CLJ_KONDO_CONFIG_FILE clj-kondo configuration file name
Use LINTER_DEFAULT to let the linter find it
CLOJURE_CLJ_KONDO_RULES_PATH Path where to find linter configuration file Workspace folder, then MegaLinter default rules
CLOJURE_CLJ_KONDO_DISABLE_ERRORS Run linter but consider errors as warnings false
CLOJURE_CLJ_KONDO_DISABLE_ERRORS_IF_LESS_THAN Maximum number of errors allowed 0

IDE Integration

Use clj-kondo in your favorite IDE to catch errors before MegaLinter !

IDE Extension Name Install
Atom linter-kondo Visit Web Site
Emacs flycheck-clj-kondo Visit Web Site
Visual Studio Code clj-kondo Install in VsCode
Visual Studio Code Clojure lint Visit Web Site

MegaLinter Flavours

This linter is available in the following flavours

Flavor Description Embedded linters Info
all Default MegaLinter Flavor 95 Docker Image Size (tag) Docker Pulls
java Optimized for JAVA based projects 42 Docker Image Size (tag) Docker Pulls

Behind the scenes

How are identified applicable files

  • File extensions: .clj, .cljs, .cljc, .edn

How the linting is performed

  • clj-kondo is called one time by identified file

Example calls

clj-kondo --lint myfile.clj
clj-kondo --lint --config .clj-kondo/config.edn myfile.clj

Help content

clj-kondo v2021.06.18


  --lint <file>: a file can either be a normal file, directory or classpath. In the
    case of a directory or classpath, only .clj, .cljs and .cljc will be
    processed. Use - as filename for reading from stdin.

  --lang <lang>: if lang cannot be derived from the file extension this option will be
    used. Supported values: clj, cljs, cljc.

  --filename <file>: in case stdin is used for linting, use this to set the
    reported filename.

  --cache-dir: when this option is provided, the cache will be resolved to this
    directory. If --cache is false, this option will be ignored.

  --cache: if false, won't use cache. Otherwise, will try to resolve cache
  using `--cache-dir`. If `--cache-dir` is not set, cache is resolved using the
  nearest `.clj-kondo` directory in the current and parent directories.

  --config <config>: config may be a file or an EDN expression. See

  --config-dir <config-dir>: use this config directory instead of auto-detected
    .clj-kondo dir.

  --parallel: lint sources in parallel.

  --dependencies: don't report any findings. Useful for populating cache while linting dependencies.

  --copy-configs: copy configs from dependencies while linting.

  --fail-level <level>: minimum severity for exit with error code.  Supported values:
    warning, error.  The default level if unspecified is warning.

Installation on mega-linter Docker image

  • Dockerfile commands :
FROM cljkondo/clj-kondo:2021.06.18-alpine as clj-kondo
COPY --from=clj-kondo /bin/clj-kondo /usr/bin/

Example success log

Results of clj-kondo linter (version 2020.09.09)
See documentation on

[SUCCESS] .automation/test/clojure/clojure_good_1.clj
    linting took 14ms, errors: 0, warnings: 0

Example error log

Results of clj-kondo linter (version 2020.09.09)
See documentation on

[ERROR] .automation/test/clojure/clojure_bad_1.clj
    .automation/test/clojure/clojure_bad_1.clj:5:5: warning: namespace clojure.set is required but never used
    .automation/test/clojure/clojure_bad_1.clj:8:2: error: unresolved symbol but-last
    .automation/test/clojure/clojure_bad_1.clj:12:1: error: clojure.string/join is called with 0 args but expects 1 or 2
    .automation/test/clojure/clojure_bad_1.clj:15:17: warning: unused binding y
    .automation/test/clojure/clojure_bad_1.clj:17:3: warning: redundant do
    .automation/test/clojure/clojure_bad_1.clj:19:5: warning: inline def
    .automation/test/clojure/clojure_bad_1.clj:22:7: warning: Redundant let expression.
    .automation/test/clojure/clojure_bad_1.clj:22:13: warning: unused binding z
    .automation/test/clojure/clojure_bad_1.clj:24:9: error: y is called with 1 arg but expects 0
    .automation/test/clojure/clojure_bad_1.clj:26:9: error: recur argument count mismatch (expected 2, got 0)
    .automation/test/clojure/clojure_bad_1.clj:29:9: error: h is called with 1 arg but expects 0
    .automation/test/clojure/clojure_bad_1.clj:30:9: error: f is called with 1 arg but expects 0
    .automation/test/clojure/clojure_bad_1.clj:34:1: warning: redefined var #'foo/private-fn
    .automation/test/clojure/clojure_bad_1.clj:34:8: warning: Unused private var foo/private-fn
    .automation/test/clojure/clojure_bad_1.clj:38:6: error: Expected: number, received: keyword.
    .automation/test/clojure/clojure_bad_1.clj:42:1: error: java.lang.Thread/sleep is called with 3 args but expects 1 or 2
    .automation/test/clojure/clojure_bad_1.clj:48:1: error: foo/foo-fn is called with 0 args but expects 2
    .automation/test/clojure/clojure_bad_1.clj:51:1: error: #'foo/private-fn is private
    .automation/test/clojure/clojure_bad_1.clj:54:7: error: duplicate key :a
    .automation/test/clojure/clojure_bad_1.clj:56:5: error: duplicate set element 1
    .automation/test/clojure/clojure_bad_1.clj:58:7: error: missing value for key :b
    .automation/test/clojure/clojure_bad_1.clj:64:3: warning: missing test assertion
    linting took 14ms, errors: 13, warnings: 9