Timothy, I probably haven't thought about this carefully enough yet, but
why do you expect the return value to be ({:x {:y 1}} nil nil) in your test
case?
Why not ({:x {:y 1}} {:x {}} nil) ?
Andy
On Fri, Feb 20, 2015 at 4:13 PM, Timothy Pratley <timothyprat...@gmail.com>
wrote:
> Alex/Rich, if a patch is welcome for this I am happy to raise a ticket and
> submit.
>
> Test case:
> (clojure.data/diff {:x {:y 1}} {:x {}})
>
> Expected:
> ({:x {:y 1}} nil nil)
>
> Actual:
> ;; => ({:x {:y 1}} {:x nil} nil)
>
> Problem:
> There is nothing only in the second input, so the second result should be
> nil.
> {:x nil} implies that there is a nil in the second input, which there is
> not.
> Furthermore the result cannot distinguish from
> (clojure.data/diff {:x {:y 1}} {:x nil})
> Which should and does correctly return {:x nil} as the second result.
>
> Affects:
> Empty collections in first or second argument
>
> Cause:
> clojure.data/diff-associative-key
> [(when (and in-a (or (not (nil? a*)) (not same))) {k a*})
> (when (and in-b (or (not (nil? b*)) (not same))) {k b*})
> (when same {k ab})]
> should be
> [(when (and in-a (or (not (nil? a*)) (and (not same) (nil? va)))) {k
> a*})
> (when (and in-b (or (not (nil? b*)) (and (not same) (nil? vb)))) {k
> b*})
> (when same {k ab})]))
>
> Why do I care?:
> I use and maintain a modest library to send state changes from Clojure to
> ClojureScript
> https://github.com/timothypratley/patchin
> In this context, handling empty collections/nils is desirable so the data
> can be treated abstractly.
> I have a workaround, so am not affected by the issue, just providing a
> motivating example where knowing the difference is useful.
>
>
>
> Regards,
> Timothy
>
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