clj-kondo

clj-kondo documentation

Version in MegaLinter: 2022.04.25
Visit Official Web Site
See How to configure clj-kondo rules
- If custom .clj-kondo/config.edn config file is not found, .clj-kondo/config.edn will be used
See How to disable clj-kondo rules in files
See Index of problems detected by clj-kondo

Configuration in MegaLinter

Enable clj-kondo by adding CLOJURE_CLJ_KONDO in ENABLE_LINTERS variable
Disable clj-kondo by adding CLOJURE_CLJ_KONDO in DISABLE_LINTERS variable

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	`file`
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	`.clj-kondo/config.edn`
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
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	97
	java	Optimized for JAVA based projects	43

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 v2022.04.25


Options:

  --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
    https://cljdoc.org/d/clj-kondo/clj-kondo/2022.04.25/doc/configuration

  --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.

  --skip-lint: skip lint/analysis, still check for other tasks like copy-configs.

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

  --debug: print debug information.

Installation on mega-linter Docker image

Dockerfile commands :

FROM cljkondo/clj-kondo:2022.04.25-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 https://megalinter.github.io/descriptors/clojure_clj_kondo/
-----------------------------------------------

[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 https://megalinter.github.io/descriptors/clojure_clj_kondo/
-----------------------------------------------

[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