Help making pull request: Ability to add `derives` clause

[oscar-broman]

I might be able to create a pull request from this, but I'd need some guidance!

This is a local diff which achieves what I'm after (circe codecs for all types):

$ git diff
diff --git a/compiler-plugin/src/main/scala/scalapb/compiler/ProtobufGenerator.scala b/compiler-plugin/src/main/scala/scalapb/compiler/ProtobufGenerator.scala
index a484b7c2..7bf3d0ba 100644
--- a/compiler-plugin/src/main/scala/scalapb/compiler/ProtobufGenerator.scala
+++ b/compiler-plugin/src/main/scala/scalapb/compiler/ProtobufGenerator.scala
@@ -1353,7 +1353,7 @@ class ProtobufGenerator(
       .indent
       .indent
       .call(printConstructorFieldList(message))
-      .add(s") extends ${message.baseClasses.mkString(" with ")} {")
+      .add(s") extends ${message.baseClasses.mkString(" with ")} derives io.circe.Codec.AsObject {")
       .call(generateSerializedSizeForPackedFields(message))
       .call(generateSerializedSize(message))
       .call(generateWriteTo(message))
diff --git a/compiler-plugin/src/main/scala/scalapb/compiler/SealedOneofsGenerator.scala b/compiler-plugin/src/main/scala/scalapb/compiler/SealedOneofsGenerator.scala
index 98217311..b3ff3dee 100644
--- a/compiler-plugin/src/main/scala/scalapb/compiler/SealedOneofsGenerator.scala
+++ b/compiler-plugin/src/main/scala/scalapb/compiler/SealedOneofsGenerator.scala
@@ -43,7 +43,7 @@ class SealedOneofsGenerator(message: Descriptor, implicits: DescriptorImplicits)
         val sealedOneofUniversalMark = if (message.isUniversalTrait) "Any with " else ""

         fp.add(
-          s"sealed trait $sealedOneofName $bases{"
+          s"sealed trait $sealedOneofName $bases derives io.circe.Codec.AsObject {"
         ).addIndented(
           s"type MessageType = $baseType",
           s"final def isEmpty = this.isInstanceOf[${sealedOneofType}.Empty.type]",
@@ -56,7 +56,7 @@ class SealedOneofsGenerator(message: Descriptor, implicits: DescriptorImplicits)
           .indented(
             _.add(s"case object Empty extends $sealedOneofType", "")
               .add(
-                s"sealed trait $sealedOneofNonEmptyName extends $sealedOneofUniversalMark$sealedOneofType"
+                s"sealed trait $sealedOneofNonEmptyName extends $sealedOneofUniversalMark$sealedOneofType derives io.circe.Codec.AsObject"
               )
               .add(
                 s"def defaultInstance: ${sealedOneofType} = Empty",

How do I add a setting for this that could be specified both globally and per message?

[thesamet]

Hi Oscar, thanks for suggesting this feature and contributing the PR. I had started to work on this in parallel, looked at your code and made adjustments in mine as necessary. One difference is that I refrained from introducing target_regex in aux_message_options but expanded target to accept * to indicate to apply to all messages in scope. Will this work for you?

I'd really appreciate before I cut a release if you will be able to try out the snapshot release 0.11.13+88-1d78ac52-SNAPSHOT and see if it works for? Some documentation is at https://github.com/scalapb/ScalaPB/blob/master/CHANGELOG.md#01114 , and

[oscar-broman]

Hi, thanks!

While I was unable to try the snapshot you published due to scalapb-runtime_3 missing for that version, I published it locally and tried it out.

There's one thing that's preventing me from not importing io.circe.generic.auto.* and that is the derives clause for GeneratedSealedOneof. Currently, only NonEmpty has the clause (and rightfully so!), but it's also needed for the top-level type.

However, I changed all sealed_value messages into sealed_value_optional and while it did increase boilerplate a bit, I got rid of some rather complex type-class derivation logic.

In the end, I'm left with the following diff required to make things work:

diff --git a/compiler-plugin/src/main/scala/scalapb/compiler/SealedOneofsGenerator.scala b/compiler-plugin/src/main/scala/scalapb/compiler/SealedOneofsGenerator.scala
index cbfce320..2f65388d 100644
--- a/compiler-plugin/src/main/scala/scalapb/compiler/SealedOneofsGenerator.scala
+++ b/compiler-plugin/src/main/scala/scalapb/compiler/SealedOneofsGenerator.scala
@@ -31,7 +31,7 @@ class SealedOneofsGenerator(message: Descriptor, implicits: DescriptorImplicits)
       val bases =
         if (baseClasses.nonEmpty)
           s"extends ${baseClasses.mkString(" with ")} $derives"
-        else ""
+        else s"$derives"
 
       if (message.sealedOneofStyle != SealedOneofStyle.Optional) {
         val sealedOneofNonEmptyName = message.sealedOneofNonEmptyScalaType.nameSymbol

[oscar-broman]

The result is amazing! 90% decrease in incremental compilation speed in many cases, and 50% reduction in clean compile.

[thesamet]

The previous commit has the diff you posted. Can you try again? I'm not sure why you were not able to use scalapb_runtime-3. Tthe new version is published on sonatype, but also the previous version did. Are your resolvers configured correctly for the project/

[oscar-broman]

Correct! I had the Sonatype snapshots configured only for the build project, and not for the project that used ScalaPB.

It works now.

[thesamet]

Perfect. Will close the issue now and cut a release soon. Don't hesitate to start a new issue or comment here if anything left unresolved.