How to Fix Validation Error in Clojure

Fixing Validation Errors in Clojure

Clojure uses clojure.spec or libraries like Malli for data validation. Validation errors surface when data doesn't conform to declared specs.

Common Causes

• Maps missing required keys
• Values not matching predicate functions
• Nested data structures with incorrect shapes

Resolution

Use spec with clear error messages:

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

(s/def ::name (s/and string? #(< 0 (count %) 100)))
(s/def ::email (s/and string? #(re-matches #".+@.+\..+" %)))
(s/def ::age (s/and int? #(< 0 % 150)))

(s/def ::user (s/keys :req-un [::name ::email]
                       :opt-un [::age]))

(defn validate-user [data]
  (if (s/valid? ::user data)
    {:ok (s/conform ::user data)}
    {:error (s/explain-str ::user data)}))

;; Usage
(validate-user {:name "Alice" :email "alice@example.com"})
;; => {:ok {:name "Alice" :email "alice@example.com"}}

(validate-user {:name "" :email "invalid"})
;; => {:error "... fails spec ::name ..."}

Return structured error data rather than throwing exceptions so callers can handle validation failures gracefully.

Avoiding Recurrence

Once you fix this error, add a regression test that reproduces the exact scenario. Document the root cause in your team's knowledge base so others can recognize the pattern. Configure monitoring alerts for early detection if the issue appears again in a different part of the codebase.

Bugsly for Clojure

Bugsly captures spec validation failures with the full data structure and the specific predicate that failed, making it easy to trace back to the data source.