> I tried with haskell and gave up when I noticed I couldn't easily get json serialization to be in the same order as the javascript implementation and therefor couldn't verify nor sign messages with interoperability with the current clients.

This gets you most of the way there:

> With the Aeson library, the order of keys in objects is undefined due to objects being implemented as HashMaps. To allow user-specified key orders in the pretty-printed JSON, encodePretty' can be configured with a comparison function.

- https://hackage.haskell.org/package/aeson-pretty-0.8.7/docs/...

I'm not sure that messes with spacing or not though or you require specific space preserving requirements to interoperate with current clients.

Even if not you can probably look at the source of encodePretty' and work out how to not mess with spacing or keep it all on one line.

I've wanted a version of Aeson for a while that preserves order and all formatting for things like linters that are very unobtrusive. It seems your use case would have benefitted from that as well.