From d9f60b6cfde0ed30290de4aefa7453d316b8acc2 Mon Sep 17 00:00:00 2001
From: kenji yoshida <6b656e6a69@gmail.com>
Date: Fri, 14 Aug 2026 02:48:02 +0900
Subject: [PATCH] [2.x] refactor: Add tailrec annotation (#9591)

---
 main/src/main/scala/sbt/ProjectExtra.scala               | 2 ++
 server-test/src/test/scala/testpkg/BuildServerTest.scala | 2 ++
 util-cache/src/main/scala/sbt/util/ActionCache.scala     | 3 ++-
 util-collection/src/test/scala/DagSpecification.scala    | 2 ++
 4 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/main/src/main/scala/sbt/ProjectExtra.scala b/main/src/main/scala/sbt/ProjectExtra.scala
index de0a13e2b..873f34902 100755
--- a/main/src/main/scala/sbt/ProjectExtra.scala
+++ b/main/src/main/scala/sbt/ProjectExtra.scala
@@ -10,6 +10,7 @@ package sbt
 import java.io.File
 import java.nio.file.Path as NioPath
 import java.net.URI
+import scala.annotation.tailrec
 // import Project._
 import Keys.{
   stateBuildStructure,
@@ -616,6 +617,7 @@ trait ProjectExtra extends Scoped.Syntax:
         projectRef: ProjectRef
     ): Seq[ProjectRef] = {
       def dependencies(map: Map[ProjectRef, Seq[ProjectRef]], id: ProjectRef): Set[ProjectRef] = {
+        @tailrec
         def helper(map: Map[ProjectRef, Seq[ProjectRef]], acc: Set[ProjectRef]): Set[ProjectRef] =
           if (acc.exists(map.contains)) {
             val (kept, rem) = map.partition { case (k, _) => acc(k) }
diff --git a/server-test/src/test/scala/testpkg/BuildServerTest.scala b/server-test/src/test/scala/testpkg/BuildServerTest.scala
index d36aae8f7..5e8a4ff38 100644
--- a/server-test/src/test/scala/testpkg/BuildServerTest.scala
+++ b/server-test/src/test/scala/testpkg/BuildServerTest.scala
@@ -20,6 +20,7 @@ import java.io.File
 import java.net.URI
 import java.nio.file.{ Files, Paths }
 import java.util.concurrent.TimeoutException
+import scala.annotation.tailrec
 import scala.concurrent.duration.*
 import scala.util.{ Failure, Success }
 
@@ -303,6 +304,7 @@ class BuildServerTest extends AbstractServerTest {
             "diagnostics for Diagnostics.scala after a failed compile (#9345)"
         )
 
+    @tailrec
     def drainQueuedNotificationsAndFailOnForbiddenReset(): Unit =
       svr.session.waitForNotificationMsg(Duration.Zero)(_ => true) match {
         case Success(n) =>
diff --git a/util-cache/src/main/scala/sbt/util/ActionCache.scala b/util-cache/src/main/scala/sbt/util/ActionCache.scala
index 292fdadff..99d1ae961 100644
--- a/util-cache/src/main/scala/sbt/util/ActionCache.scala
+++ b/util-cache/src/main/scala/sbt/util/ActionCache.scala
@@ -32,7 +32,7 @@ import sbt.nio.file.{ **, FileTreeView }
 import sbt.nio.file.syntax.*
 import sbt.util.CacheImplicits
 import scala.reflect.ClassTag
-import scala.annotation.{ meta, StaticAnnotation }
+import scala.annotation.{ meta, tailrec, StaticAnnotation }
 import scala.collection.mutable
 import scala.util.control.NonFatal
 import sjsonnew.{ HashWriter, JsonFormat }
@@ -329,6 +329,7 @@ object ActionCache:
     )
 
   /** Walks `t`'s cause chain for a `NoSuchFileException`, returning the missing file's path. */
+  @tailrec
   private[sbt] def findMissingFile(t: Throwable): Option[String] =
     t match
       case null                   => None
diff --git a/util-collection/src/test/scala/DagSpecification.scala b/util-collection/src/test/scala/DagSpecification.scala
index 45bb8cecc..3c301a664 100644
--- a/util-collection/src/test/scala/DagSpecification.scala
+++ b/util-collection/src/test/scala/DagSpecification.scala
@@ -11,6 +11,7 @@ package sbt.internal.util
 import org.scalacheck.*
 import Prop.*
 
+import scala.annotation.tailrec
 import scala.collection.mutable.HashSet
 
 object DagSpecification extends Properties("Dag") {
@@ -41,6 +42,7 @@ object DagSpecification extends Properties("Dag") {
   private def isSet[T](c: Seq[T]) = Set(c*).size == c.size
   private def dependenciesPrecedeNodes(sort: List[TestDag]) = {
     val seen = new HashSet[TestDag]
+    @tailrec
     def iterate(remaining: List[TestDag]): Boolean = {
       remaining match {
         case Nil          => true