Agreed; I was just following up on your previous comments. But, it is useful to have something that can be used in a precondition and also shows an explanation.
I’m using, basically, (or (s/valid? spec x) (s/explain spec x)). It would be good to have this built-in too. From: clojure@googlegroups.com [mailto:clojure@googlegroups.com] On Behalf Of Alex Miller Sent: Wednesday, June 7, 2017 5:46 PM To: Clojure <clojure@googlegroups.com> Subject: Re: clojure.spec - Using :pre conditions (or not)? Preconditions are already assertions, so it makes more sense to use s/assert in your code body than in a precondition. On Wednesday, June 7, 2017 at 8:12:22 AM UTC-5, David Goldfarb wrote: One big downside of using s/assert in a precondition: It does not work with (s/nilable ...) specs, since s/assert returns valid values. I fell into this trap for a moment of head-scratching just now. On Wednesday, September 14, 2016 at 4:59:09 PM UTC+3, Alex Miller wrote: Another option that has been added since the guide was written is s/assert which seems closer to what you're suggesting. (defn name [user] {:pre [(s/assert :common/user user)]} (-> user :user/name)) ;; need to enable assertion checking - this can also be enabled globally with system property clojure.spec.check-asserts (s/check-asserts true) (name {:user/name "Elon"}) "Elon" (name {:x "Elon"}) ExceptionInfo Spec assertion failed val: {:x "Elon"} fails predicate: (contains? % :user/name) :clojure.spec/failure :assertion-failed clojure.core/ex-info (core.clj:4725) Rather than use it in a precondition, you can also use s/assert directly in the code. On Wednesday, September 14, 2016 at 7:37:24 AM UTC-5, joakim.t...@nova.com<mailto:joakim.t...@nova.com> wrote: (ns spec-test.core (:require [clojure.spec :as s])) (s/def :user/name string?) (s/def :common/user (s/keys :req [:user/name])) ; first version of name (using :pre) (defn name [user] {:pre [(s/valid? :common/user user)]} (-> user :user/name)) ; This statement works ok and returns "Elon": (name {:user/name "Elon"}) ; but this statement... (name {:x "Elon"}) ;...will throw: CompilerException java.lang.AssertionError: Assert failed: (s/valid? :common/user user) ; ...but then I don't get as much information ; about the error as if I would have called: (s/explain :common/user {:x "Elon"}) ;...which also contains the predicate: val: {:x "Elon"} fails spec: :common/user predicate: (contains? % :user/name) ; (second version of name - more verbose) ; or do I need to wite it like this: (defn name [user] (let [parsed (s/conform :common/user user)] (if (= parsed ::s/invalid) (throw (ex-info "Invalid input" (s/explain-data :common/user user))) (-> user :user/name)))) ; so that: (name {:x "Elon"}) ; ...will return: CompilerException clojure.lang.ExceptionInfo: Invalid input #:clojure.spec{:problems} ({:path [], :pred (contains? % :user/name), :val {:x "Elon"}, :via [:common/user], :in []}) ; It should be nice if I could be able to write it like this ; (or similar, to get a better error message): (defn name [user] {:pre [(s/explain :common/user user)]} (-> user :user/name)) -- You received this message because you are subscribed to the Google Groups "Clojure" group. To post to this group, send email to clojure@googlegroups.com<mailto:clojure@googlegroups.com> Note that posts from new members are moderated - please be patient with your first post. To unsubscribe from this group, send email to clojure+unsubscr...@googlegroups.com<mailto:clojure+unsubscr...@googlegroups.com> For more options, visit this group at http://groups.google.com/group/clojure?hl=en --- You received this message because you are subscribed to a topic in the Google Groups "Clojure" group. To unsubscribe from this topic, visit https://groups.google.com/d/topic/clojure/H9tk04sSTWE/unsubscribe. To unsubscribe from this group and all its topics, send an email to clojure+unsubscr...@googlegroups.com<mailto:clojure+unsubscr...@googlegroups.com>. For more options, visit https://groups.google.com/d/optout. -- You received this message because you are subscribed to the Google Groups "Clojure" group. To post to this group, send email to clojure@googlegroups.com Note that posts from new members are moderated - please be patient with your first post. To unsubscribe from this group, send email to clojure+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/clojure?hl=en --- You received this message because you are subscribed to the Google Groups "Clojure" group. To unsubscribe from this group and stop receiving emails from it, send an email to clojure+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
