Support clojure-lsp/unused-public-var for custom macros

[mrkam2]

• I have read the Clojure etiquette and will respect it when communicating on this platform.

problem

clojure-lsp/unused-public-var linter is quite useful but sometimes we want to suppress it. For example, in a situation when a variable is defined by a custom macro and that's the correct behavior. For such cases, this linter has a useful :exclude-when-defined-by option. Unfortunately, when a hook is used, this option doesn't help much because the custom macro name is not propagated to the linter when a hook is used. In particular, definition parameter received by clojure-lsp.queries/exclude-public-definition? function contains the following two fields (which it then exercises):

  :defined-by clojure.core/defn,
  :defined-by->lint-as clojure.core/defn,

As Eric suggested in slack comment, when :analyze-call hook is used, it can provide additional :defined-by field on the returned map:

(defn defflow [{:keys [node]}]
  ...
    {:node ...
     :defined-by 'state-flow.cljtest/defflow}))

This causes the definition parameter to contain these values instead:

  :defined-by state-flow.cljtest/defflow,
  :defined-by->lint-as clojure.core/defn,

Unfortunately, this is not done by default and there seems to be no way to have it work for :macroexpand hooks.

I looked at the code and I figured that with a small modifications, this information can be always supplied for all the hooks.

Here is the proposed diff: master...mrkam2:clj-kondo:patch-2

Example

I have a macro that defines two variables:

(ns myns)
(defmacro mydef [db n & body]
  `(do (defn ~(str n "-foo") [] (with-open [_# ~db] ~@body))
       (defn ~(str n "-bar") [] (with-open [_# ~db] ~@body))))

I then define a :macroexpand hook with roughly the same content. There are situations when the client code only uses one of these variables and they're being flagged by unused-public-var linter. The simplest solution would be to provide the following config:

{:linters {:clojure-lsp/unused-public-var {:exclude-when-defined-by #{myns/mydef}}}}

But this wouldn't work as when this linter receives the information about these n-foo and n-bar vars their attributes show them as defined by defn and not mydef.

Slack discussion: https://clojurians.slack.com/archives/CPABC1H61/p1706756199608299?thread_ts=1688068718.797849&cid=CPABC1H61.

[borkdude]

I'd be fine with that, if you could also add some tests