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

Tim Bray <tbray@textuality.com> Thu, 28 February 2013 21:59 UTC

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Date: Thu, 28 Feb 2013 13:59:37 -0800
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From: Tim Bray <tbray@textuality.com>
To: Paul Hoffman <paul.hoffman@vpnc.org>
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Cc: Nico Williams <nico@cryptonector.com>, Barry Leiba <barryleiba@computer.org>, "json@ietf.org" <json@ietf.org>
Subject: Re: [Json] What does "break compatibility" mean?
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If there were a significant number of protocols, or deployed software
components, that relied on the use of multiple keys, then changing the
SHOULD to a MUST would be a breaking change. I do not believe that there
are any, and thus this is not, *de facto*, a breaking change.  That
hypothesis is easily falsified, if in the course of the IETF work someone
sticks their hand up and says “this is going to break me”.  But I’m not
holding my breath.

 -T


On Thu, Feb 28, 2013 at 1:51 PM, Paul Hoffman <paul.hoffman@vpnc.org> wrote:

> On Feb 28, 2013, at 12:46 PM, Nico Williams <nico@cryptonector.com> wrote:
>
> > On Thu, Feb 28, 2013 at 2:06 PM, Tim Bray <tbray@textuality.com> wrote:
> >> It’s clear to me that, *for the purposes of the IETF*, someone needs to
> say
> >> “People sending JSON MUST NOT use duplicate keys.”  The fact that
> certain
> >> libraries allow less-clueful developers to do this, and that parsing
> >> software is observed to behave unpredictably when they do, should only
> >> encourage us.
> >
> > The obvious compromise is to say senders MUST NOT send dup object keys
> > and receivers MUST take the last key value pair of any dup keys,
> > per-ECMAScript.  The latter preserves compatibility.
>
> ...but the former ("say senders MUST NOT send dup object keys") breaks it,
> given that the RFC had a SHOULD not a MUST. Thus the question in this
> thread.
>
> --Paul Hoffman
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