[2.x] Opt bspBuildTargetOutputPathsItem out of caching (#9272)

Opt bspBuildTargetOutputPathsItem out of caching

main/src/main/scala/sbt/Keys.scala

@@ -483,6 +483,7 @@ object Keys {
   val bspBuildTargetDependencySources = inputKey[Unit]("").withRank(DTask)
   val bspBuildTargetDependencySourcesItem = taskKey[DependencySourcesItem]("").withRank(DTask)
   val bspBuildTargetOutputPaths = inputKey[Unit]("").withRank(DTask)
+  @transient
   val bspBuildTargetOutputPathsItem = taskKey[OutputPathsItem]("").withRank(DTask)
   val bspBuildTargetCompile = inputKey[Unit]("").withRank(DTask)
   val bspBuildTargetCompileItem = taskKey[Int]("").withRank(DTask)

sbt-app/src/sbt-test/server/bsp-output-paths-cache/build.sbt

@@ -0,0 +1,30 @@
+import sbt.internal.bsp.OutputPathsItem
+
+ThisBuild / scalaVersion := "3.8.2"
+
+name := "bsp-output-paths-cache"
+
+Compile / target := baseDirectory.value / "target-a"
+
+@transient
+lazy val checkProjectA = taskKey[Unit]("")
+
+@transient
+lazy val checkProjectB = taskKey[Unit]("")
+
+def checkOutputPath(item: OutputPathsItem, expectedSegment: String): Unit = {
+  val actual = item.outputPaths.map(_.uri.toString).mkString("\n")
+  if (!actual.contains(expectedSegment)) {
+    sys.error(
+      s"stale bspBuildTargetOutputPathsItem: expected segment $expectedSegment in output paths, got: $actual"
+    )
+  }
+}
+
+checkProjectA := Def.uncached {
+  checkOutputPath((Compile / bspBuildTargetOutputPathsItem).value, "target-a")
+}
+
+checkProjectB := Def.uncached {
+  checkOutputPath((Compile / bspBuildTargetOutputPathsItem).value, "target-b")
+}

sbt-app/src/sbt-test/server/bsp-output-paths-cache/test

@@ -0,0 +1,3 @@
+> checkProjectA
+> set Compile / target := baseDirectory.value / "target-b"
+> checkProjectB