Transformation from Tuple10 and onwards is broken

[VladKopanev]

Checklist

• I read the documentation at https://chimney.readthedocs.io/ and checked that the functionality exists
• I verified that the behavior for my use case doesn't match the documentation
• I checked the https://github.com/scalalandio/chimney/issues and haven't found the issue reported
  • I checked the https://github.com/scala/bug/issues and haven't found the issue reported there - relevant for Scala 2 compiler crashes, since it might be a bug in the compiler
  • I checked the https://github.com/lampepfl/dotty/issues and haven't found the issue reported there - relevant for Scala 3 compiler crashes, since it might be a bug in the compiler
• I confirmed that the bug is not related to functionality that was deprecated: lifted transformers (TransformerFs) or unsafeOption flags
• I believe that this is actual bug, rather than a question how to use existing features

Describe the bug

When transforming from Tuple10,11..N compilation fails with message like:
`Chimney can't derive transformation from scala.Tuple10[java.lang.String, java.lang.String, java.lang.String, java.lang.String, scala.Some[java.lang.String], scala.Double, java.lang.String, java.lang.String, java.lang.String, java.lang.String] to Playground.Order

Reproduction

https://scastie.scala-lang.org/VladKopanev/G7wkbDmoTPieFaoLMxfFIA/18

If posting a snippet, test it first with scala-cli run --server=false .!

Expected behavior

I expect transformation from Tuple10 to case class to compile. The same code snipped works if version of the library is changed to chimney 1.7.3

Actual behavior

Chimney can't derive transformation from scala.Tuple10[java.lang.String, java.lang.String, java.lang.String, java.lang.String, scala.Some[java.lang.String], scala.Double, java.lang.String, java.lang.String, java.lang.String, java.lang.String] to Playground.Order

Playground.Order
totalAmount: scala.Double - can't derive transformation from totalAmount: scala.Some[java.lang.String] in source type scala.Tuple10[java.lang.String, java.lang.String, java.lang.String, java.lang.String, scala.Some[java.lang.String], scala.Double, java.lang.String, java.lang.String, java.lang.String, java.lang.String]
currency: java.lang.String - can't derive transformation from currency: scala.Double in source type scala.Tuple10[java.lang.String, java.lang.String, java.lang.String, java.lang.String, scala.Some[java.lang.String], scala.Double, java.lang.String, java.lang.String, java.lang.String, java.lang.String]

scala.Double (transforming from: _5 into: totalAmount)
derivation from tuple10._5: scala.Some[java.lang.String] to scala.Double is not supported in Chimney!

java.lang.String (transforming from: _6 into: currency)
derivation from tuple10._6: scala.Double to java.lang.String is not supported in Chimney!

Which Chimney version do you use

1.8.0 with Scala 3.6.4

Which platform do you use

• JVM
• Scala.js
• Scala Native

If you checked JVM

Which JVM distribution do you use (you can provide java -version output).

Additional context

Add any other context about the problem here.

[MateuszKubuszok]

Analysis of getters returned fields in wrong order:

    + Resolved scala.Tuple10[java.lang.String, java.lang.String, java.lang.String, java.lang.String, scala.Some[java.lang.String], scala.Double, java.lang.String, java.lang.String, java.lang.String, java.lang.String] getters: (`_1`: java.lang.String (ConstructorArgVal, declared), `_10`: java.lang.String (ConstructorArgVal, declared), `_2`: java.lang.String (ConstructorArgVal, declared), `_3`: java.lang.String (ConstructorArgVal, declared), `_4`: java.lang.String (ConstructorArgVal, declared), `_5`: scala.Some[java.lang.String] (ConstructorArgVal, declared), `_6`: scala.Double (ConstructorArgVal, declared), `_7`: java.lang.String (ConstructorArgVal, declared), `_8`: java.lang.String (ConstructorArgVal, declared), `_9`: java.lang.String (ConstructorArgVal, declared), `toArray`: scala.Array[java.lang.Object] (AccessorMethod, inherited), `toIArray`: scala.IArray$package.IArray[java.lang.Object] (AccessorMethod, inherited), `toList`: scala.collection.immutable.List[scala.Tuple.Union[scala.Tuple10[java.lang.String, java.lang.String, java.lang.String, java.lang.String, scala.Some[java.lang.String], scala.Double, java.lang.String, java.lang.String, java.lang.String, java.lang.String]]] (AccessorMethod, inherited)) and Playground.Order constructor (`userId`: java.lang.String (ConstructorParameter, default = None), `orderId`: java.lang.String (ConstructorParameter, default = None), `customerId`: java.lang.String (ConstructorParameter, default = None), `orderDate`: java.lang.String (ConstructorParameter, default = None), `shippingDate`: scala.Option[java.lang.String] (ConstructorParameter, default = None), `totalAmount`: scala.Double (ConstructorParameter, default = None), `currency`: java.lang.String (ConstructorParameter, default = None), `status`: java.lang.String (ConstructorParameter, default = None), `shippingAddress`: java.lang.String (ConstructorParameter, default = None), `billingAddress`: java.lang.String (ConstructorParameter, default = None), `items`: scala.collection.immutable.List[Playground.OrderItem] (ConstructorParameter, default = None)), using position-based matching (tuple present)

Since they are supposed to be sorted by the order of occurrence in source code it means that there is something wrong about Tuples - name is used as a fallback when the line/column information is absent, so that's probably it.

So that would require Scala 3-specific workaround for missing information in Tuples' symbols.

[VladKopanev]

Please note that the same snipped compiles normally and produces the expected result in runtime when used with Chimney 1.7.3.

From the error it also interesting that it looks as if the order of fields in tuple just shifts 1 position forward when matching with case class fields

[MateuszKubuszok]

Yes, that's what I said: fields should be extracted as sequence _1, _2, ..., _9, _10, sorted by position in code, but they are sorted by name: _1, _10, _2, ..., _9.

Name started being used as fallback in sorting of enums due to scala/scala3#21672, and later code was refactored to share the same implementation in scalalandio/chimney-macro-commons@fb82edc.

If name is being used then Position for Tuples is broken. If it worked before then it was actually accidental as pos.start returned 0, and apparently the sorting algorithm was stable, and left them in the original ordering (kinda relying on undefined behavior). So again, it needs Scala 3 specific-fix to make it work deterministically for tuples.

[VladKopanev]

Cool, does that mean with 1.7.3 it's indeterministic and can break unexpectedly in the runtime?

[MateuszKubuszok]

More like it relies on Community Build to detect that changes of undocumented behavior of some methods would make some library no longer compile.

[MateuszKubuszok]

@VladKopanev, if you are interested in fixing this issue, I can guide you. In the foreseeable future, I do not have time for Chimney maintenance, so I can reply and guide others but I am not doing any work here.

[VladKopanev]

@MateuszKubuszok, sounds good, once I'm free I can take it!