unused bindings

[borkdude]

Report unused bindings

TODO:

• suppress warning when using a binding that starts with an underscore, e.g. (fn [_] "foo")
• false positive: (fn [{:keys [x] :or {x 1}}] x)
• false positive: (let [{:keys [patient/id order/id]} {}] id) (both are unused, while in reality only one is unused)
• support loop, if-let, when-let
• support for for, doseq, with-open
• handle :let, :when and :while in for and doseq
• look more closely to defmacro locals + syntax-quote
• emit warnings when something is not a valid binding form
• fix false positives with locals used in metadata

Linux binary: https://3192-176829714-gh.circle-artifacts.com/0/release/clj-kondo-2019.05.27-alpha-SNAPSHOT-linux-amd64.zip
Mac binary: https://3194-176829714-gh.circle-artifacts.com/0/release/clj-kondo-2019.05.27-alpha-SNAPSHOT-macos-amd64.zip

[borkdude]

@mynomoto A very preliminary version of unused bindings is supported in this linux binary (EDIT: link moved to opening comment)
Since you asked for this feature, I'd appreciate it if you could test a bit with it and report your findings. As of now it only reports unused bindings in let, if-let, when-let, fn, loop and defn.

[mynomoto]

Sure, will do and report.

[mynomoto]

Found one false positive

(defn false-positive-bind
  [{:keys [:x]}]
  (if-let [x (identity x)]
    x
    :y))

Reports: cljkondo.clj:2:12: warning: unused binding x

[mynomoto]

Changing if-let to when-let causes the same problem. It's not related to the destructuring of :x.

[borkdude]

@mynomoto Please ensure you're using the latest binary linked in the top comment. I believe I've already fixed this in the last few hours :-).

[mynomoto]

I just finished linting a project from work and no more false positives after the upgrade. Thanks!

[mynomoto]

I would love for this to cover cats.core/mlet (it works just like a let) but I'm not sure if you intend to or not in this first version. I wonder if that could be configurable for well behaved forms.

[borkdude]

@mynomoto That should work when using :lint-as {cats.core/mlet clojure.core/let} in the configuration.

[borkdude]

Fixed with 6d9020a

[mynomoto]

@mynomoto That should work when using :lint-as {cats.core/mlet clojure.core/let} in the configuration.

Cool, I will try that! Thanks!

[mynomoto]

Found a false positive related to metadata:

(defn false-positive-metadata
  [a b]
  ^{:key (str a b)} [:other])

cljkondo.clj:2:4: warning: unused binding a
cljkondo.clj:2:6: warning: unused binding b

[borkdude]

Good catch! I'll look into it.

[borkdude]

@mynomoto Fixed in https://3192-176829714-gh.circle-artifacts.com/0/release/clj-kondo-2019.05.27-alpha-SNAPSHOT-linux-amd64.zip
Can you test? I also found this catched a false positive here:
https://github.com/clojure/clojure/blob/8c402a8c9695a4eddc07cbbe0d95d44e1372f0bf/src/clj/clojure/zip.clj#L31

[mynomoto]

The false positive fix worked, as the :lint-as configuration. Thanks!

[svdo]

I think I'm getting a false positive on my CLJS code. I'm using a default import (:require ["react-native-view-overflow" :default ViewOverflow]) and this gives a warning: "namespace react-native-view-overflow is required but never used".

Other than that no surprises :)