2013.4.0.0 proposal

Mark Lentczner mark.lentczner at gmail.com
Wed Nov 13 19:33:37 UTC 2013

I'd like to better understand the backwards compatibility of these changes,
and this new major bump of aeson:

On Mon, Nov 11, 2013 at 2:07 AM, Bas van Dijk <v.dijk.bas at gmail.com> wrote:

> Note that I removed the blaze-builder requirement from aeson-HEAD (it
>  now uses the Builder from bytestring with a fallback to blaze-builder
> when configured with -fblaze-builder).

Which we'd have to do for this HP, as the bytestring package is
from the GHC release. Hence, the blaze-builder requirement would still be

> I think we're pretty close to a release of aeson- It would be
> great to have this version in the HP since:

I'm concerned about timing. In particular, how long should a new major
version bump release be out before one is confident that it won't need a
minor rev. ( soon?

> * It includes an important bug fix for the eitherDecodeStrict functions

Well, that seems good. Could that get back ported on top of if we
decided to not do a major bump this time?

>  * It has support for arbitrary precision floating point numbers (as

required by the JSON spec) through the Scientific type.

Well, one can argue if that is what the spec says - but in practice, JSON
libraries in other systems don't use arbitrary precision floating point
(nor does any JavaScript implementation that I know of).

Those issues aside, how does the API evolve? What is the plan for
introducing this functionality without breaking existing aeson relying
code? aeson's Number constructor points to Number from attoparsec which has
only two constructors: I Integer and D Double. Wouldn't introducing a
third, or replacing D, break existing uses of aeson?

* It removes the ByteString instances since JSON doesn't have support
> for binary data (this was brought up during the HP inclusion
> discussion).

Do we have any usage stats to know if any code uses this show instance?
Again, trying to avoid breaking compiling code. Were deprecation notices
added to the package at some point?

- Mark
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