Option to preserve key order relying on toEncoding

[fizruk]

Right now the keys are always resorted when using encodePretty.
However, sometimes it is desired to preserve the key order from toEncoding.

See GetShopTV/swagger2#98 for a possible use case.

[eltix]

This would definitely a plus. Right now there are many cases where we cannot use encodePretty (and use encode from Data.Aeson instead) because of this.

[guibou]

I'm interested by this issue.

Unfortunately, toEncoding yields a Builder which does not contain any structure anymore, so it is not possible to format it again, except by converting it back to Value with decode, but the order will be lost.

[martijnbastiaan]

IMO this is a pretty serious issue that conflicts with this library's core mission:

The library provides a single function encodePretty. It is a drop-in replacement for aeson's encode function, producing JSON-ByteStrings for human readers.

[theophile-scrive]

@informatikr @DougBurke Would you be open to a PR that fixes this behaviour?

[martijnbastiaan]

@theophile-scrive I've taken over maintainership for this package. I'd definitely be interested!

[theophile-scrive]

@martijnbastiaan Very well. :)