I tend to agree with you in where the benefit is - it's just that the
way the protocol docs are phrased, and some of the language used in that
mailing discussion from 10 years ago (from authoritative sources like
Rich and Stuart), implies that /no library is to extend clojure.core
protocols to core Java objects/, and that only Clojure itself is allowed
do that. The example Stuart gave back then with the
english/spelling-corrector VS spanish/spelling-corrector is pretty
telling...
Could it perhaps be the case that `Datafiable` is somewhat special in
that, it was conceived for the purpose of open extension by third
parties, and that the protocol extension guidelines don't really apply
to it (or perhaps not as strictly)?
Thanks for taking the time :)
Dimitris
On 31/01/2020 01:23, Sean Corfield wrote:
If your library is intended specifically to provide the ability to
datafy/nav java.time objects then it is something optional that users
can choose to opt into.
The section you meant to link to
https://clojure.org/reference/protocols#_guidelines_for_extension
says: “To minimize conflicts, consider these guidelines”
So they’re a) guidelines and b) just given as a caution to minimize
conflicts.
There are libraries out there already that exist specifically to give
users the option to extend protocols from one library (such as
clojure.java.jdbc or next.jdbc) to Java types to provide customized
behavior, above and beyond the “base versions for common targets”
mentioned in that section provided by the original library.
I see benefit in libraries that extend Clojure’s datafy/nav to new
domains as a narrow purpose that users can opt into. I see much less
benefit in providing the same protocols and function names that core
already includes, targeted to new types, in an isolated way such as
this. Perhaps that is because I’m already using datafy/nav and I find
their utility is enhanced by being extended to other Java types?
Yes, if multiple people write multiple libraries A, B, C that extend
datafy/nav to java.time types and then other libraries X, Y, Z start
pulling in those extenders, consumers of X, Y, Z can be in trouble.
Sean Corfield -- (904) 302-SEAN
An Architect's View -- http://corfield.org/
"If you're not annoying somebody, you're not really alive."
-- Margaret Atwood
*From: *dimitris <mailto:jimpil1...@gmail.com>
*Sent: *Thursday, January 30, 2020 9:58 AM
*To: *clojure@googlegroups.com <mailto:clojure@googlegroups.com>
*Subject: *Re: Feedback on datafy/nav project
Well, the official Clojure guidelines are to NOT extend protocols,
unless you own either the protocol of the type(s) [1].
In particular these lines:
/If you are a library developer, you should not extend if you own
neither the protocol nor the target./
/You should take particular care when extending protocols included
with Clojure itself./
Kind regards,
Dimitris
[1]: https://clojure.org/reference/protocols#_extend_via_metadata
On 30/01/2020 17:50, Sean Corfield wrote:
Is there a reason you’ve mirrored those protocols/implementations
rather than just use Clojure’s built-in versions?
As it stands, your library wouldn’t work with other tooling that
builds on Clojure’s datafy/nav (REBL, for example).
Sean Corfield -- (904) 302-SEAN
An Architect's View -- http://corfield.org/
"If you're not annoying somebody, you're not really alive."
-- Margaret Atwood
*From: *dimitris <mailto:jimpil1...@gmail.com>
*Sent: *Thursday, January 30, 2020 9:05 AM
*To: *Clojure <mailto:clojure@googlegroups.com>
*Subject: *Feedback on datafy/nav project
Hi folks,
I'm looking for honest and constructive feedback on [1] - not so much
about the actual implementation (even though these are welcome
too), but
rather about the general idea of basing everything on top of
(mirrored
versions) `datafy` and `nav` (in this way). There is a TL;DR
section at
the very bottom that describes the approach in 4 short sentences.
Many thanks in advance,
Dimitris
[1]: https://github.com/jimpil/jedi-time
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