spectacular

spec / instrument arbitrary Clojure expressions!

(require '[spectacular.core :refer [with-spec]])

(let [a 100
      b "2"]
  (with-spec {a integer?
              b string?}
    string?
    (str a b)))

Why?

Specs are great! Let's have more of them.

Usage

[spectacular "0.2.0"]

(require '[spectacular.core :as s])

Specs will be checked iff (s/check-asserts?) evaluates to true, which it doesn't by default.

This can be achieved in two ways:

• (s/check-asserts true) enables all spec asserts globally
• s/with-check-asserts sets spec-checking on/off for its body:

(s/with-check-asserts true
  (let [a 100
        b "2"]
    (s/with-spec {a integer?
                  b string?}
      string?
      (str a b))))

We can just check existing bindings:

(s/with-check-asserts true
  (let [a 100
        b "2"]
    (s/with-spec-in {a integer?
                     b string?}
      (str a b))))

or just the returned value:

(s/with-check-asserts true
  (let [a 100
        b "2"]
    (s/with-spec-out string?
      (str a b))))

or even entire functions:

(require '[clojure.spec.alpha :as sa])

(let [palindrome? (fn [s]
                    (s/with-spec {s (sa/and string? not-empty)}
                      boolean?
                      (= (seq s) (reverse s))))]
  (s/with-check-asserts true
    (palindrome? "pop")))

Note

Get better error messages with expound.

(require [expound.alpha :as e])

(set! sa/*explain-out* e/printer)

License

Copyright © 2018 Divyansh Prakash

Distributed under the Eclipse Public License either version 1.0.