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Truss

Assertions micro-library for Clojure/Script

Truss is a tiny Clojure/Script library that provides fast and flexible runtime assertions with terrific error messages. Use it as a complement or alternative to clojure.spec, core.typed, etc.

A doubtful friend is worse than a certain enemy. Let a man be one thing or the other, and we then know how to meet him. - Aesop

Latest release/s

2024-09-07 1.12.0: release info

See here for earlier releases.

Why Truss?

Tiny cross-platform Clj/s codebase with zero dependencies
Trivially easy to learn, use, and understand
Terrific error messages for quick+easy debugging
Terrific performance: miniscule (!) runtime cost
Easy elision for zero runtime cost
No commitment or costly buy-in: use it just when+where needed
Perfect for library authors: no bulky dependencies

Video demo

See for intro and usage:

Quick example

(require '[taoensso.truss :as truss :refer [have have?]])

;; Truss uses the simple `(predicate arg)` pattern familiar to Clojure users:
(defn square [n]
  (let [n (have integer? n)] ; <- A Truss assertion
    (* n n)))

;; This assertion basically expands to:
;; (if (integer? n) n (throw-detailed-assertion-error!))

(square 5)   ; => 25
(square nil) ; =>
;; Invariant failed at truss-examples[9,11]: (integer? n)
;; {:dt #inst "2023-07-31T09:56:10.295-00:00",
;;  :pred clojure.core/integer?,
;;  :arg {:form n, :value nil, :type nil},
;;  :env {:elidable? true, :*assert* true},
;;  :loc
;;  {:ns truss-examples,
;;   :line 9,
;;   :column 11,
;;   :file "examples.cljc"}}

;; Assert inside collections using `:in`:
(have string? :in ["don't" "panic"])

That's everything most users will need to know, but see the documentation below for more!

Documentation

Wiki (getting started, usage, etc.)
API reference: cljdoc or Codox

Funding

You can help support continued work on this project, thank you!! 🙏

License