Fix Java output when export pipelining is disabled

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

@@ -2325,13 +2325,11 @@ object Defaults extends BuildCommon with DefExtra {
     val reporter = (compile / bspReporter).value
     val log = CompileDebugLogger(projectId, s.log)
     try {
-      if (r.hasModified) {
+      val result0 = incCompiler
-        val result0 = incCompiler
+        .asInstanceOf[sbt.internal.inc.IncrementalCompilerImpl]
-          .asInstanceOf[sbt.internal.inc.IncrementalCompilerImpl]
+        .compileAllJava(in, log)
-          .compileAllJava(in, log)
+      reporter.sendSuccessReport(result0.analysis())
-        reporter.sendSuccessReport(result0.analysis())
+      result0.withHasModified(result0.hasModified || r.hasModified)
-        result0.withHasModified(result0.hasModified || r.hasModified)
-      } else r
     } catch {
       case NonFatal(e) =>
         reporter.sendFailureReport(in.options.sources)
@@ -4415,8 +4413,8 @@ object Classpaths {
   def makeProducts: Initialize[Task[Seq[File]]] = Def.task {
     val c = fileConverter.value
     val resourceDirs = resourceDirectories.value
-    val vfBackendDir = compileIncremental.value._2
+    val _ = compile.value
-    val backendDir = c.toPath(vfBackendDir)
+    val backendDir = c.toPath(backendOutput.value)
     val _ = resources.value
     backendDir.toFile() :: resourceDirs.toList.filter(_.exists())
   }

sbt-app/src/sbt-test/source-dependencies/pipelining-java-scala-no-export/build.sbt

@@ -0,0 +1,14 @@
+ThisBuild / scalaVersion := "2.13.18"
+ThisBuild / usePipelining := true
+
+lazy val root = (project in file("."))
+  .aggregate(upstream, downstream)
+
+lazy val upstream = project
+  .settings(
+    exportJars := true,
+    exportPipelining := false,
+  )
+
+lazy val downstream = project
+  .dependsOn(upstream)

sbt-app/src/sbt-test/source-dependencies/pipelining-java-scala-no-export/downstream/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-no-export/test

@@ -0,0 +1,4 @@
+> compile
+
+$ exists target/**/upstream/classes/example/Greeter.class
+$ exists target/**/downstream/classes/example/Main.class

sbt-app/src/sbt-test/source-dependencies/pipelining-java-scala-no-export/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-no-export/upstream/src/main/scala/example/Marker.scala

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