Add an API to choose the underlying JSON encoder.

[clokep]

This is an alternative to #24, which allows for better backwards compatibility for a period of time. It lets libraries depending on canonicaljson opt into using a different JSON implementation.

[clokep]

See #26 for the failing builds.

[clokep]

This is probably ready to go, minus some CI issues.

[clokep]

See matrix-org/synapse#7674 for how this would be used.

[anoadragon453]

I'm a bit confused, as we seem to use simplejson in this library because we think it better performant than stdlib json. Yet we're adding functionality to allow using json as we in Synapse think it's more performant than simplejson?

I'm guessing we're doing this so that the library implementation won't change from under other people using canonicaljson? Could we do that via a version bump of canonicaljson instead?

[clokep]

@anoadragon453 There's a bunch of conversation about this in matrix-org/synapse#7674 (comment), but the gist is:

• Synapse doesn't put a max version on the canonicaljson dependency, so any change must be backwards compatible to not break a new install of an old Synapse.
• The goal of this is to allow Synapse to NOT use simplejson, in a backwards compatible fashion. The approach taken here is that it is backwards compatible unless you opt into new behavior.

as we seem to use simplejson in this library because we think it better performant than stdlib json

We used to think this, the latest profiling done shows this to no longer be true.

Let me know if that clears things up or not!

[anoadragon453]

Ahh, I see now. We're not only worrying about other users of this library, but also old versions of Synapse. Makes sense 🙂

as we seem to use simplejson in this library because we think it better performant than stdlib json

We used to think this, the latest profiling done shows this to no longer be true.

Yes, I was thinking we should just change the default in this library to always be stdlib json based on the new benchmark data, but I'm guessing that would be a backwards incompatible change.

[clokep]

but I'm guessing that would be a backwards incompatible change.

The standard library JSON on Python 3.5 doesn't handle bytes well, so...yeah it isn't backwards compatible. Hopefully we can do that at some point in the future!

[anoadragon453]

That clears things up then. Thanks!