Question 1

How to validate function arguments with Truss in Clojure?

Accepted Answer

Use the `have` macro inline or in let bindings, e.g., `(defn my-fn [x] (have string? x) ...)`. It throws detailed exceptions on failure, including the argument value and source location for easier debugging.

Question 2

Truss vs Slingshot – which is better for error handling?

Accepted Answer

Truss focuses on improving error messages and adding context, making it ideal for debugging opaque errors. Slingshot offers more flexible error catching and resumable exceptions, so choose Truss for clarity or Slingshot for advanced control.

Question 3

Does Truss work with ClojureScript?

Accepted Answer

Yes, Truss is designed for both Clojure and ClojureScript, with cross-platform utilities like `catching` and `try*` that function identically. The library is dependency-free and tested on both platforms.

Question 4

How to add Ring request context to exceptions with Truss?

Accepted Answer

Wrap your Ring handler with `truss/with-ctx+` to merge the request into `*ctx*`, as shown in the `wrap-ring-ctx` example. This ensures any thrown `truss/ex-info` includes the Ring request for debugging.

Question 5

Can I disable Truss assertions in production for performance?

Accepted Answer

Truss doesn't provide a built-in way to disable assertions; they are runtime checks. For performance-critical sections, you may need to manually remove or conditionally include them, which adds maintenance complexity.

Question 6

What special predicates does Truss have support?

Accepted Answer

Truss supports predicates like `[:or nil? string?]` for unions, `[:ks<= #{:a :b}]` for map keys, `[:el #{:a :b :c}]` for set membership, and `[:n<= 10]` for collection sizes, as detailed in the inline assertions section.

Truss

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