Sorting of case class properties no longer works as of 2.20

[brharrington]

Can be reproduced with the following test case:

diff --git a/src/test/scala/com/fasterxml/jackson/module/scala/ser/CaseClassSerializerTest.scala b/src/test/scala/com/fasterxml/jackson/module/scala/ser/CaseClassSerializerTest.scala
index 6dc1d665..33dddf06 100644
--- a/src/test/scala/com/fasterxml/jackson/module/scala/ser/CaseClassSerializerTest.scala
+++ b/src/test/scala/com/fasterxml/jackson/module/scala/ser/CaseClassSerializerTest.scala
@@ -2,6 +2,9 @@ package com.fasterxml.jackson.module.scala.ser
 
 import com.fasterxml.jackson.annotation.JsonProperty.Access
 import com.fasterxml.jackson.annotation._
+import com.fasterxml.jackson.databind.MapperFeature
 import com.fasterxml.jackson.databind.{ObjectMapper, PropertyNamingStrategies}
 import com.fasterxml.jackson.module.scala.DefaultScalaModule
 
@@ -62,6 +65,8 @@ case class PrivateDefaultFields(
 case class ClassWithUnitField(field: Unit, intField: Int)
 case class ClassWithOnlyUnitField(field: Unit)
 
+case class ClassWithUnorderedFields(f3: Int = 3, f2: Int = 2, f0: Int = 0, f1: Int = 1)
+
 class CaseClassSerializerTest extends SerializerTest {
 
   case class NestedClass(field: String)
@@ -207,4 +212,11 @@ class CaseClassSerializerTest extends SerializerTest {
     serialize(GeneratedDefaultArgumentClass()) shouldEqual "{}"
   }
 
+  it should "sort properties of the case class" in {
+    val mapper = newBuilder
+      .configure(MapperFeature.SORT_PROPERTIES_ALPHABETICALLY, true)
+      .build()
+    serialize(ClassWithUnorderedFields(), mapper) shouldEqual """{"f0":0,"f1":1,"f2":2,"f3":3}"""
+  }
+
 }

This test cases passes with 2.19.2 and fails with 2.20.0. I thought it might be related to FasterXML/jackson-databind#3900, but disabling MapperFeature.SORT_CREATOR_PROPERTIES_FIRST does not resolve the issue.

[brharrington]

Looks like it might be related to: 30bd026. Should that honor the MapperFeature.SORT_CREATOR_PROPERTIES_FIRST flag rather than always return false and use the order for the class?

[pjfanning]

I don't know what to do here. Changes in jackson-databind have made life complicated. Most Scala users want jackson-module-scala to order the parameters of the case class by their declared order. 2.20 is designed to ease the transition to Jackson 3 where MapperFeature.SORT_PROPERTIES_ALPHABETICALLY defaults to true.
I might try to hack a new config into jackson-module-scala 3 and then see what can be done in 2.20.
I don't want to respect MapperFeature.SORT_PROPERTIES_ALPHABETICALLY at the moment because it breaks too much.

Right now, I have no idea what to do here and am in no rush to dig myself deeper into trouble. 30bd026 fixed more than it broke, I'm afraid.

If you absolutely must use jackson 2.20, you could declare JsonPropertyOrder annotations and hopefully, jackson-databind should respect those.
https://www.baeldung.com/jackson-annotations#3-jsonpropertyorder

I will never have time to write test coverage for every single Jackson config option and annotation permutation

[pjfanning]

#773 fixes the issue on 3.0.x by checking if MapperFeature.SORT_CREATOR_PROPERTIES_FIRST is disabled

This won't work in 2.x because the method that changed in 3 does not pass the MapperConfig in 2.x.
It will need to remain broken until I find a way to hack a different solution for 2.x.

[brharrington]

Thanks for the prompt response and fix. Fixing forward is probably fine at least for my use-case, I can look into updating to 3.x.

[pjfanning]

Another solution that you could try is registering your own module on mapper (or mapper builder if you want to use the more modern approach). This extra module could add an AnnotationIntrospector that has a findSerializationSortAlphabetically method that returns true for everything.