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Derivation of codecs with Dotty (Scala 3)
See original GitHub issueCurrently jsoniter-scala uses some features of experimental Scala 2 macros which are not ported to Scala 3. They are described in the following PR to the Scala Migration Guide.
Two possible solutions:
- Port
Evals.evalto Scala 3 - Redesign jsoniter-scala-macros API to avoid usage of
Evals.evalcalls and refactor jsoniter-scala-core implementation to avoideval.evalcalls (see dependency onexpression-evaluator).
Issue Analytics
- State:
- Created 5 years ago
- Reactions:18
- Comments:14 (8 by maintainers)
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Here: https://github.com/rssh/jsoniter-scala/tree/scala3 is an attempt to port existing macros to scala3.
I make it compiled but not yet run. Note, that this attempt was porting with minimal changes, I have not tried to improve code organization.
Possible local next step – look at the first errors in the tests compilation logs
, extract this error into small reproducible examples and submit it to the dotty team or discover our own bug. repeat.
I think, porting existing code is possible but time-consuming [i.e. marathon, not sprint]. (I’m not sure that I can allocate an appropriate time budget for this, but maybe somebody can start from that point.
Only one thing, which is used in current macros and has no direct analog in dotty is access to the default values of primary constructors. (see https://github.com/lampepfl/dotty/discussions/14078 ), eventually, it is possible to extend the tasty reflection API.
Also, I’m not sure that the current approach is ideal – maybe better to write derivation from scratch, (not checked this, an idea to write all derivation inside some trait from which an instance of configuration is accessible). Differences are not very big, from the other side – code organization can be better) In case, if I have had enough time, I have started to explore this way.
In any case, It would be good to see branch ‘scala3-experiment’ here. (and maybe create a new subproject to explore dotty-only derivation)
@domdorn Yes, you can! It is available on the Maven Central. Please try and send your feedback.