[2.0.x] Remove Path type from caching (#9036)

**Problem**
Like File, Path normally captures the absolute path,
so likely not a good candidate for caching.

**Solution**
Ban it.

---------

Co-authored-by: Anatolii Kmetiuk <anatoliikmt@proton.me>

core-macros/src/main/scala/sbt/internal/util/appmacro/Cont.scala

@@ -3,6 +3,8 @@ package internal
 package util
 package appmacro
 
+import java.io.File
+import java.nio.file.{ Path as NioPath }
 import scala.collection.mutable.ListBuffer
 import scala.reflect.ClassTag
 import scala.quoted.*
@@ -177,11 +179,11 @@ trait Cont:
       val (expr, treeType) = eitherTree match
         case Left(l)  => (l, TypeRepr.of[Effect[A]])
         case Right(r) => (r, faTpe)
-
+      val fileRepr = TypeRepr.of[File]
+      val pathRepr = TypeRepr.of[NioPath]
       def containsFileType[A1: Type]: Boolean =
-        val fileRepr = TypeRepr.of[java.io.File]
         def containsFile(tpe: TypeRepr): Boolean =
-          if tpe =:= fileRepr then true
+          if tpe =:= fileRepr || tpe =:= pathRepr then true
           else
             tpe.dealias match
               case AppliedType(_, args) => args.exists(containsFile)
@@ -354,7 +356,7 @@ trait Cont:
       )(body: Expr[A1], input: Expr[A2]): Expr[A1] =
         if containsFileType[A1] then
           report.errorAndAbort(
-            s"""java.io.File is not a valid output type for a cached task.
+            s"""java.io.File and Path are not valid output types for a cached task.
                |Consider using one of the following alternatives:
                |  - xsbti.HashedVirtualFileRef
                |  - xsbti.VirtualFileRef

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

@@ -28,8 +28,11 @@ object Keys {
   case object IgnoreSourceChanges extends WatchBuildSourceOption
   case object WarnOnSourceChanges extends WatchBuildSourceOption
   case object ReloadOnSourceChanges extends WatchBuildSourceOption
+
+  @transient
   val allInputFiles =
     taskKey[Seq[Path]]("All of the file inputs for a task excluding directories and hidden files.")
+  @transient
   val changedInputFiles =
     taskKey[Seq[(Path, FileStamp)] => FileChanges]("The changed files for a task")
   val fileInputs = settingKey[Seq[Glob]](
@@ -50,8 +53,10 @@ object Keys {
     settingKey[PathFilter]("A filter to apply to the outputs of a task.")
   val fileOutputExcludeFilter =
     settingKey[PathFilter]("An exclusion filter to apply to the outputs of a task.")
+  @transient
   val allOutputFiles =
     taskKey[Seq[Path]]("All of the file outputs for a task excluding directories and hidden files.")
+  @transient
   val changedOutputFiles =
     taskKey[Seq[(Path, FileStamp)] => FileChanges](
       "The files that have changed since the last task run."
@@ -158,9 +163,12 @@ object Keys {
   private[sbt] val dynamicFileOutputs =
     taskKey[Seq[Path]]("The outputs of a task").withRank(Invisible)
 
+  @transient
   val inputFileStamps =
     taskKey[Seq[(Path, FileStamp)]]("Retrieves the hashes for a set of task input files")
       .withRank(Invisible)
+
+  @transient
   val outputFileStamps =
     taskKey[Seq[(Path, FileStamp)]]("Retrieves the hashes for a set of task output files")
       .withRank(Invisible)
@@ -181,9 +189,11 @@ object Keys {
   private[sbt] val managedFileStampCache = taskKey[FileStamp.Cache](
     "Map of managed file stamps that may be cleared between task evaluation runs."
   ).withRank(Invisible)
+  @transient
   private[sbt] val managedSourcePaths =
     taskKey[Seq[Path]]("Transforms the managedSources to Seq[Path] to induce setting injection.")
       .withRank(Invisible)
+  @transient
   private[sbt] val dependencyClasspathFiles =
     taskKey[Seq[Path]]("The dependency classpath for a task.").withRank(Invisible)
   private[sbt] val compileOutputs = taskKey[Seq[Path]]("Compilation outputs").withRank(Invisible)

sbt-app/src/sbt-test/nio/dynamic-outputs/build.sbt

@@ -1,6 +1,7 @@
 import java.nio.file.{ Path, Paths }
 import sbt.internal.FileChangesMacro.inputFiles
 
+@transient
 val foo = taskKey[Seq[Path]]("Copy files")
 foo / fileInputs += baseDirectory.value.toGlob / "base" / "*.txt"
 foo / target := baseDirectory.value / "out"

sbt-app/src/sbt-test/nio/input-filters/build.sbt

@@ -2,6 +2,7 @@ import java.nio.file.{ Files, Path }
 import sbt.internal.FileChangesMacro.inputFiles
 import sbt.internal.FileChangesMacro.outputFiles
 
+@transient
 val copyPaths = taskKey[Seq[Path]]("Copy paths")
 copyPaths / fileInputs += baseDirectory.value.toGlob / "inputs" / *
 copyPaths := {

sbt-app/src/sbt-test/nio/output-filters/build.sbt

@@ -1,5 +1,6 @@
 import java.nio.file.{ Files, Path }
 
+@transient
 val outputTask = taskKey[Seq[Path]]("A task that generates outputs")
 outputTask := {
   val dir = Files.createDirectories(streams.value.cacheDirectory.toPath)

sbt-app/src/sbt-test/nio/overrides/build.sbt

@@ -1,5 +1,6 @@
 import java.nio.file.Path
 
+@transient
 val foo = taskKey[Path]("foo")
 // Check a direct override
 foo / outputFileStamps := Nil
@@ -7,12 +8,14 @@ foo := baseDirectory.value.toPath / "foo.txt"
 
 TaskKey[Unit]("checkFoo") := assert((foo / outputFileStamps).value == Nil)
 
+@transient
 val bar = taskKey[Path]("bar")
 // Check an append
 bar / outputFileStamps ++= (baz / outputFileStamps).value
 bar / outputFileStamps ++= (baz / outputFileStamps).value
 bar := baseDirectory.value.toPath / "bar.txt"
 
+@transient
 val baz = taskKey[Path]("baz")
 baz := baseDirectory.value.toPath / "baz.txt"