Example of using Telemere with Bling (rich text console printing lib for Clj/s+)

telemere-bling-example.clj

;; Example created: 2024-12-23
;;    Last updated: 2025-03-11 by @paintparty

;; Dependencies:
;;   Telemere - Ref. https://github.com/taoensso/telemere v1.0.0-RC5 (2025-03-10)
;;   Bling    - Ref. https://github.com/paintparty/bling  v0.5.2     (2025-03-11)

;; Platform: Clj only for now (haven't tried yet with Cljs)
;; Improvements very welcome!

;; Original context: https://github.com/taoensso/telemere/issues/33

(require '[taoensso.telemere       :as tel])
(require '[taoensso.telemere.utils :as tel-utils])
(require '[bling.core              :as bling])

(defn- signal->callout-opts
  "Returns {:keys [type label data?]} for use with `bling/callout`, etc."
  [{:keys [level]}]
  (let [label (tel-utils/format-level level)
        type
        (case level
          (:report :info) :info
          (:fatal :error) :error
          (:warn)         :warning
          (do             nil))
        colorway
        (case level
          (:trace :debug) :subtle
          (do             :neutral))]

    {:type type,
     :colorway colorway
     :label label,
     :data? true,
     :margin-top 0,
     :margin-bottom 1}))

(tel/add-handler! :my-bling-handler
  (let [;; Set your preferred formatting options below as usual:
        format-signal-fn (tel/format-signal-fn {:incl-newline? false})
        my-output-fn
        (fn [signal]
          (let [norm-output (format-signal-fn signal)] ; Normal Telemere output
            (bling.core/callout ; Add Bling "callout" formatting
              (signal->callout-opts signal)
              norm-output)))]

    (tel/handler:console {:output-fn my-output-fn})))

Thanks yourself Jeremiah for a very useful (and fun) library

Re. colour translation choices --they're entirely my fault. Had spent some of the afternoon writing an indexed-db handler for telemere, which reminded me that I'd stolen this gist ages ago but not used it because it wasn't compatible with the cljs-devtools formatters. Did this quickly for fun before shuttting down -- first asked claude to format the log preamble using 'appropriate colors -- e.g. red for error, orange for warning'. Its initial choice for :info was green -- so then asked it to use blue instead, then to use a darker blue -- and here we are :) I'lll certainly use the semantic aliases you've provided going forward.