When function is throwing exception because of argument. I would prefer to
throw IllegalArgumentException not AssertionError.
(defn check [type data]
(if (sp/valid? type data)
true
(throw (IllegalArgumentException. (sp/explain type data)))))
Br,
Mamun
On Friday, September 16, 2016 at 7:20:53 AM UTC+2, joakim.t...@nova.com
wrote:
>
> I came up with this solution:
>
> (ns spec-test.core
> (:require [clojure.spec :as s]))
>
> (s/def :user/name string?)
> (s/def :common/user (s/keys :req [:user/name]))
>
> ;; with this little helper function...
> (defn check [type data]
> (if (s/valid? type data)
> true
> (throw (AssertionError. (s/explain type data)))))
>
> ;; I can use it in my :pre condition
> (defn aname [user]
> {:pre [(check :common/user user)]}
> (-> user :user/name))
>
> ;; when I call name with an illegal arguement...
> (aname {:x "Elon"})
>
> ;; ...it not fails and returns a better error message:
> CompilerException java.lang.AssertionError: null,
> compiling:(/Users/joakimtengstrand/IdeaProjects/spec-test/src/spec_test/core.clj:19:1)
> val: {:x "Elon"} fails spec: :common/user predicate: (contains? % :user/name)
>
>
> With this solution I don't need to enable assertions, and the code is neat
> and less verbose!
>
> /Joakim
>
> On Thursday, September 15, 2016 at 3:11:32 PM UTC+2, Shantanu Kumar wrote:
>>
>> 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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