µPickle VS jsoniter-scala

The upickle library has traditionally had great performance for handling json in Scala apps so is likely to be seen as a safe choice for someone starting a Scala project. It appears though that not just upickle, but other json library projects are having difficulties maintaining their old level of performance when they release using Scala 3's macros. uPickle currently has an open issue where you can see some of these issues: https://github.com/com-lihaoyi/upickle/issues/389 and here you can see the weePickle folks are also having the same performance problems. Looks like things changed up significantly enough between Scala 2 and Scala 3 so that in order to maintain the same functionality they have resorted to using runtime reflection for mapping to/from case classes.

See here for sample code size numbers (not picking on upickle specifically, it's just what I'm using myself. I've heard similar reports about e.g. circe)

A good starting point is the note in MacroImplicits.scala in upickle sources. "derives Writer" for a specific case class Foo simply adds a given Writer[Foo] to a companion object of the same specific class. However, this cannot be done automatically for a trait defining sum type - in this case trait Thing. The required given must be defined manually, and the ones automatically obtained for case classes can be used in it.

What an amazing step by step explanation!

More than 2 years ago I found that byte array view var handles are quite suitable to cook efficient SWAR routines with Java/Scala.

See a lot of other examples of SWAR usage, like parsing Base16/64 string, java.time.* and number values directly from byte arrays:

https://github.com/plokhotnyuk/jsoniter-scala/blob/master/js...

Afaik dsl-json came up with a lot of improvements and inspired a several other libraries like JsonIter and jsonIter-scala. Jsoniter-scala by u/plokhotnyuk is probably the most optimized JSON library on the JVM at this point, and seems to power most of the Scala ecosystem. Some implementations/optimizations eventually made their way back into Jackson and other libraries.

I was on your place more then 5 years ago, when cut the 1st release of jsoniter-scala.

I've just increased compiler performance in ~1.5x times by adding these JVM options for the code cache

We have our own open-source code-generator that produces Scala code from Smithy. The code module is entirely dependency-free, and the generated code is not biased towards any library, be that http or json. We do however have out-of-the-box integration with jsoniter and http4s.

You can use jsoniter-scala. It is easy to use like upickle.

BTW, jsoniter-scala uses it for faster parsing and serialization using SWAR techniques, like here.

Probably you should have both codecs (for Foo and for its T) are implicitly available in the scope, like it is done in the following test for jsoniter-scala:

BEWARE: uJson is vulnerable under DoS attacks

Please see sources (and GitHub history of development) of jsoniter-scala as an example in the domain of JSON parsing and serialization.