Michiel Borkent @borkdude

Word origins

Clojure linters Linter Focus CLJS? Macroexpand? Execution Eastwood General No core + user JVM Kibit Idioms No No JVM Joker General Yes core Go native Cljfmt Formatting Yes n/a JVM How to ns How to ns Yes n/a Clojure JVM Clj-kondo General Yes core GraalVM native / JVM

Clj-kondo origin story • I've been a happy joker user since 2017 • Wanted to add a feature: (defn foo [x] (def x 1)) • Joker is written in Go, can it be done in Clojure? • Tried with Clojure on GraalVM (native = fast startup like joker) • Success with rewrite-clj which is based on tools.reader • Writing more linting features was too much fun!

Invalid code is still data

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Arity errors

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REPL state

REPL state $ clj-kondo --lint src | grep "unresolved symbol c" src/dre/analytics/authors.clj:585:41: info: unresolved symbol c

Unused let and fn bindings

Unresolved symbols

Redundant let + do

Missing test assertion

Style: don't refer :all

Ns form cleanup

Ns form cleanup

Type checking

Editor support

.clj-kondo • .clj-kondo/config.edn • Shared configuration, intended for version control • .clj-kondo/.cache • Automatically updated when changing code in editor • Contains arity and other info about linted code • Allows linter to reason about multiple namespaces • Populate with lib info: clj-kondo --lint $(clj -Spath)

Config from manifold.deferred Clj-kondo doesn't know how to lint this macro

Config

Analysis export

Who uses clj-kondo? Github #438 Add your company to the list:

Thank you https://github.com/borkdude/clj-kondo