From 7f57e4d6a6c3b0c3b7707aeae116fe52cb8999dc Mon Sep 17 00:00:00 2001
From: Yannick Heiber <ybasket42@googlemail.com>
Date: Sun, 27 Sep 2026 17:21:43 +0200
Subject: [PATCH 1/3] Use future lazy val encoding

Scala 3.3.8 allows to opt in to the lazy val encoding Scala 3.8+ uses to avoid warnings/errors on JVM 25+. As we already bumped the minimum JDK version to 17, the fact that future lazy vals require 9+ is no problem. On the positive side, we avoid our users getting annoyed (or having to resort to bytecode manipulation via VirtusLab/sloth) when using JVM 25 or higher.
---
 build.sbt | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/build.sbt b/build.sbt
index e0d2b670..9b3f993f 100644
--- a/build.sbt
+++ b/build.sbt
@@ -79,7 +79,7 @@ val commonSettings = List(
           "-Wconf:msg=type parameter .+ defined in .+ shadows .+:s", // esp.Tag
           "-Wconf:msg=value T is deprecated:s" // jsonpath/xpath literals
         )
-      case Some((3, _)) => List("-source:3.2-migration", "-no-indent")
+      case Some((3, _)) => List("-source:3.2-migration", "-no-indent", "-Yfuture-lazy-vals")
     }
     .toList
     .flatten,

From 3f3686b295642a7bdbbf393dd7e90f403647fb6f Mon Sep 17 00:00:00 2001
From: Yannick Heiber <ybasket42@googlemail.com>
Date: Mon, 28 Sep 2026 13:14:33 +0200
Subject: [PATCH 2/3] Attempt to make MiMa happy on future lazy vals

---
 build.sbt | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/build.sbt b/build.sbt
index 9b3f993f..df60b1cd 100644
--- a/build.sbt
+++ b/build.sbt
@@ -205,7 +205,9 @@ lazy val csv = crossProject(JVMPlatform, JSPlatform, NativePlatform)
     description := "Streaming CSV manipulation library",
     mimaBinaryIssueFilters ++= List(
       // Static forwarder, only relevant for Java
-      ProblemFilters.exclude[DirectMissingMethodProblem]("fs2.data.csv.RowEncoderF.fromNonEmptyMapCsvRowEncoder")
+      ProblemFilters.exclude[DirectMissingMethodProblem]("fs2.data.csv.RowEncoderF.fromNonEmptyMapCsvRowEncoder"),
+      // Static initializer forwarder, not callable. Scala 3 only, due to future lazy val encoding
+      ProblemFilters.exclude[DirectMissingMethodProblem]("fs2.data.csv.CellDecoder.<clinit>")
     )
   )
   .jsSettings(
@@ -316,7 +318,11 @@ lazy val json = crossProject(JVMPlatform, JSPlatform, NativePlatform)
       ProblemFilters.exclude[MissingClassProblem]("fs2.data.json.jsonpath.internals.TaggedJson$StartArrayElement$"),
       ProblemFilters.exclude[MissingClassProblem]("fs2.data.json.jsonpath.internals.TaggedJson$StartObjectValue"),
       ProblemFilters.exclude[MissingClassProblem]("fs2.data.json.jsonpath.internals.TaggedJson$StartObjectValue$"),
-      ProblemFilters.exclude[DirectMissingMethodProblem]("fs2.data.json.jsonpath.package.untag")
+      ProblemFilters.exclude[DirectMissingMethodProblem]("fs2.data.json.jsonpath.package.untag"),
+      // Static initializer forwarders, not callable. Scala 3 only, due to future lazy val encoding
+      ProblemFilters.exclude[DirectMissingMethodProblem]("fs2.data.json.Selector.<clinit>"),
+      ProblemFilters.exclude[DirectMissingMethodProblem]("fs2.data.json.NamePredicate.<clinit>"),
+      ProblemFilters.exclude[DirectMissingMethodProblem]("fs2.data.json.IndexPredicate.<clinit>")
     )
   )
   .nativeSettings(

From e2c4e6e3591326d96386be706849f5876c69f5ca Mon Sep 17 00:00:00 2001
From: Yannick Heiber <ybasket42@googlemail.com>
Date: Fri, 2 Oct 2026 10:29:24 +0200
Subject: [PATCH 3/3] Do not use future lazy vals on Native yet

---
 build.sbt | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/build.sbt b/build.sbt
index df60b1cd..1d115498 100644
--- a/build.sbt
+++ b/build.sbt
@@ -79,10 +79,16 @@ val commonSettings = List(
           "-Wconf:msg=type parameter .+ defined in .+ shadows .+:s", // esp.Tag
           "-Wconf:msg=value T is deprecated:s" // jsonpath/xpath literals
         )
-      case Some((3, _)) => List("-source:3.2-migration", "-no-indent", "-Yfuture-lazy-vals")
+      case Some((3, _)) => List("-source:3.2-migration", "-no-indent")
     }
     .toList
     .flatten,
+  // Scala Native's nscplugin for 3.3.8 cannot handle VarHandle-based lazy vals (scala-native/scala-native#4957)
+  scalacOptions ++= {
+    if (scalaBinaryVersion.value == "3" && !crossProjectPlatform.?.value.contains(NativePlatform))
+      List("-Yfuture-lazy-vals")
+    else Nil
+  },
   scalacOptions ++= PartialFunction
     .condOpt(CrossVersion.partialVersion(scalaVersion.value)) {
       case Some((2, n)) if n >= 13 =>