Re: [Json] What does "break compatibility" mean?

Paul Hoffman <paul.hoffman@vpnc.org> Fri, 01 March 2013 15:31 UTC

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Subject: Re: [Json] What does "break compatibility" mean?
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On Mar 1, 2013, at 2:01 AM, Martin J. Dürst <duerst@it.aoyama.ac.jp> wrote:

> Putting the horse before the chart, I think we don't want to break compatibility, but where necessary, we want to improve interoperability. Senders that send two of the same keys in the same object, and receivers that take any other than the last one, both create interoperability problems. Fixing that is valuable progress.

Yes.

> Using a standard language lawyer approach, I think we can observe that changing the SHOULD NOT to a MUST NOT should be okay because SHOULD NOT means that you can do it if you have a really good reason for it, but I haven't yet seen anybody come up with a good reason for it, so I'd claim that the cases with duplicate keys that exist out in the wild actually don't comply to the current spec.

That's not true at all. A perfectly valid reason for a JSON producer to put in two or more of the same name is a streaming producer that doesn't know what has been added before. Changing SHOULD NOT to MUST NOT means that a JSON producer MUST know everything else in the object before emitting it. It would be reasonable for this to be the consensus, but we can't say that it does not break compatibility with some producers. (And, of course, the other option is to break compatibility with some JSON processors.)

--Paul Hoffman