Hi Joakim,
You might be interested in Paul Stadig's library
https://github.com/pjstadig/assertions that leverages Java's `-ea`
(enable-assertions, which you may want to keep enabled in dev) command-line
flag. If you have a bunch of things together to assert, you may want to use
the `when-assert` macro for wholesale
optimization:
https://github.com/pjstadig/assertions/blob/0.2.0/src/pjstadig/assertions.clj#L13
Shantanu
On Thursday, 15 September 2016 16:50:17 UTC+5:30, joakim.t...@nova.com
wrote:
>
> Ok, thanks!
>
> In the Java world, the assertions is also something that need to be turn
> on explicitly.
> In that sence, they are kind of not mandatory to be executed (or at least
> signals that to the reader of the code).
>
> I would be happier if you guys could add another method, that I can use in
> my :pre conditions, that leverage
> the same amount of details in the error messages, but that is always
> "turned on".
>
> In the meanwhile, I will use s/assert ;-)
>
> BR,
> Joakim Tengstrand
>
>
> On Wednesday, 14 September 2016 15:59:09 UTC+2, 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 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))
>>>
>>>
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