Fix #9343 route pipelined dependencyPicklePath through internalDependencyPicklePath (#9425)

main/src/main/scala/sbt/Defaults.scala

@@ -2839,7 +2839,7 @@ object Classpaths {
             case (false, _) =>
               Def.task { filteredDependencyClasspath.value }
             case (true, DependencyMode.Transitive) =>
-              Def.task { dependencyClasspath.value }
+              Def.task { internalDependencyPicklePath.value ++ externalDependencyClasspath.value }
             case (true, DependencyMode.Direct) =>
               Def.task {
                 val internalFiltered = ClasspathImpl.filterInternalByMode(
@@ -2847,7 +2847,7 @@ object Classpaths {
                   thisProjectRef.value,
                   settingsData.value,
                   buildDependencies.value,
-                  internalDependencyClasspath.value,
+                  internalDependencyPicklePath.value,
                 )
                 val externalFiltered = ClasspathImpl.filterByDirectDeps(
                   allDependencies.value,
@@ -2862,7 +2862,7 @@ object Classpaths {
                   thisProjectRef.value,
                   settingsData.value,
                   buildDependencies.value,
-                  internalDependencyClasspath.value,
+                  internalDependencyPicklePath.value,
                 )
                 val externalFiltered = ClasspathImpl.filterByPlusOne(
                   allDependencies.value,

sbt-app/src/sbt-test/source-dependencies/pipelining-java-scala/build.sbt

@@ -0,0 +1,28 @@
+ThisBuild / scalaVersion := "2.13.18"
+ThisBuild / usePipelining := true
+
+lazy val root = (project in file("."))
+  .aggregate(upstream, `downstream-transitive`, `downstream-direct`, `downstream-plusone`)
+  .settings(
+    name := "pipelining Java then Scala",
+  )
+
+lazy val upstream = project
+
+lazy val `downstream-transitive` = project
+  .in(file("downstream-transitive"))
+  .dependsOn(upstream)
+
+lazy val `downstream-direct` = project
+  .in(file("downstream-direct"))
+  .dependsOn(upstream)
+  .settings(
+    dependencyMode := DependencyMode.Direct,
+  )
+
+lazy val `downstream-plusone` = project
+  .in(file("downstream-plusone"))
+  .dependsOn(upstream)
+  .settings(
+    dependencyMode := DependencyMode.PlusOne,
+  )

sbt-app/src/sbt-test/source-dependencies/pipelining-java-scala/downstream-direct/src/main/scala/example/Main.scala

@@ -0,0 +1,5 @@
+package example
+
+object Main {
+  def run(): String = Greeter.greet("world")
+}

sbt-app/src/sbt-test/source-dependencies/pipelining-java-scala/downstream-plusone/src/main/scala/example/Main.scala

@@ -0,0 +1,5 @@
+package example
+
+object Main {
+  def run(): String = Greeter.greet("world")
+}

sbt-app/src/sbt-test/source-dependencies/pipelining-java-scala/downstream-transitive/src/main/scala/example/Main.scala

@@ -0,0 +1,5 @@
+package example
+
+object Main {
+  def run(): String = Greeter.greet("world")
+}

sbt-app/src/sbt-test/source-dependencies/pipelining-java-scala/test

@@ -0,0 +1,13 @@
+# Regression test for https://github.com/sbt/sbt/issues/9343
+# With usePipelining := true, a downstream Scala source that references a
+# Java class defined in an upstream project must still compile; the early
+# pickle artifacts from upstream must stay visible on the pipelined classpath.
+# Three downstream projects exercise Transitive, Direct, and PlusOne modes.
+# A single aggregate compile fans out from one upstream pickle-producing task
+# to all three downstream compilations without reusing a pipelining promise.
+
+> compile
+
+$ exists target/**/downstream-transitive/classes/example/Main.class
+$ exists target/**/downstream-direct/classes/example/Main.class
+$ exists target/**/downstream-plusone/classes/example/Main.class

sbt-app/src/sbt-test/source-dependencies/pipelining-java-scala/upstream/src/main/java/example/Greeter.java

@@ -0,0 +1,7 @@
+package example;
+
+public class Greeter {
+  public static String greet(String name) {
+    return "Hello, " + name;
+  }
+}

sbt-app/src/sbt-test/source-dependencies/pipelining-java-scala/upstream/src/main/scala/example/Marker.scala

@@ -0,0 +1,5 @@
+package example
+
+object Marker {
+  val tag = "upstream"
+}