In this stage of the workshop, still have src/hooks_workshop/macro_usage.clj open in your editor!
Remember that kdefn3 (and all other kdefns) takes a vector of keywords
instead of symbols:
(kdefn3 my-fn3 [:foo :bar] (+ foo baz))A common error when calling this macro is that people pass symbols instead of keywords. Wouldn't it be great if clj-kondo could warn you while you're typing?
This is what the api/reg-finding! function is for. It takes a map with
location information: :row, :end-row, :col, :end-col, a :type (the
linter keyword identifier), and a :message.
Remember that location information is stored as metadata on nodes. So to call reg-finding! we can just take the metadata of a node and add the :type and :message key:
(api/reg-finding! (assoc (meta node) :type :my-lib/my-linter :message "This is bad!"))To support a custom linter, there must be a configuration entry that sets the
default lint warning :level, which the user can tweak or turn :off
completely:
In .clj-kondo/config.edn:
{:linters {my-lib/my-linter {:level :warning}}}Without this, clj-kondo will ignore the custom linter even if calls to reg-finding! were made.
When creating custom linters it is recommended to use namespaced keywords that
contain an organization name or library name. For example clojure-lsp has one
custom linter with the name :clojure-lsp/unused-public-var. This way, your
custom linter will never conflict with a name that clj-kondo or another library
chooses.
Let's add a custom lint warning named :hooks-workshop/kdefn-args which prints
a warning when people call kdefn3 like this:
(kdefn3 my-fn [a])
^ Expected keyword, but got symbol: a