I welcome the strict checking over backwards compatibility for broken
syntax. E. g. allowing things like symbols in the ns decl would require
supporting that as a feature in future updates, analyzer code, other hosts
etc. The Clojure devs should not have to worry things with so little use.
Still the error messages are simply far from good enough and that is what
appears to me as the main problem OP has. If the compiler had pointed him
to two fixes he could have done in a minute then he had not complained and
instead felt more happy with his new compiler.
Here is my story when I loaded a large codebase today with 1.9-alpha11:
Call to clojure.core/defn did not conform to spec: In: [1 0] val:
({:keys [money/major money/minor money/currency], :or #:money{major
0, minor 0, currency :EUR}}) fails spec:
:clojure.core.specs/arg-list at: [:args :bs :arity-1 :args]
predicate: (cat :args (* :clojure.core.specs/binding-form) :varargs
(? (cat :amp #{(quote &)} :form
:clojure.core.specs/binding-form))), Extra input In: [1 0] val:
{:keys [money/major money/minor money/currency], :or #:money{major
0, minor 0, currency :EUR}} fails spec:
:clojure.core.specs/arg-list at: [:args :bs :arity-n :bodies :args]
predicate: vector? :clojure.spec/args (format-money [{:keys
[money/major money/minor money/currency], :or #:money{major 0,
minor 0, currency :EUR}}] (str major "," (if (zero? minor) "-"
minor) " €"))
I know where the problem is immediately because I looked at above error
and quickly jumped to the code that didn't work. Then I guessed it right
because I know what has been changed from Alex Release notes and because I
had recently inquired on this board about :or destructoring and probably
because I am a long time Clojure user. The problem is that :or in map
destructuring with namespaced keywords was not officially supported before
1.9 (but sadly worked exactly opposite to how it is supported now)
Compare that the more common story of someone who has not followed every
newspiece lately and just wants to upgrade from 1.8 to 1.9 - How could he
tell whats wrong from above error message? Following above error message by
looking up specs and following index paths like [1 0] is a manual process
that costs and feels like debugging a difficultly hidden bug. The
time/utility distance to a hand written macro assert like "Keys in :or
destructoring must be unqualified symbols" currently does not justify the
use of specs for such things. It's by far worse than the NPE Stacktraces
popping up from nowhere that one learns to value and utilize after a month
or so in Clojure.
It seems that improving the error messages we can calculate from specs data
is something that more people should think about and improve for 1.9. I'd
be willing to invest time if needed / input is welcome. Alternatively a way
to integrate custom error messages into specs directly could also be
helpful.
(But I still don't really see how above spec tells me that I shouldn't use
qualified symbols in :or destructoring - do you?)
On Monday, August 22, 2016 at 5:08:57 PM UTC+2, Alex Miller wrote:
>
> I've added library related fixes related to core specs to an info page at:
>
> http://dev.clojure.org/display/design/Errors+found+with+core+specs
>
>
> On Sunday, August 21, 2016 at 8:24:20 PM UTC-5, Alex Miller wrote:
>>
>> On Sunday, August 21, 2016 at 5:28:57 PM UTC-5, lvh wrote:
>>>
>>> FYI, while I disagree with your conclusion (I think we should go fix
>>> libraries instead), I ran into the same issue just now for roughly the same
>>> reason, except the thing that pulled in an old version of core.unify was
>>> core.typed, which pulls in 0.5.3 through core.contracts.
>>>
>>
>> BTW, core.contracts was also updated to 0.0.6 last week to use the latest
>> core.unify.
>>
>>
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