From 8b5eaa2cd507291fb7d96740e7832892107c9664 Mon Sep 17 00:00:00 2001
From: Adrien Piquerez <adrien.piquerez@gmail.com>
Date: Fri, 1 Nov 2024 17:57:42 +0100
Subject: [PATCH] Cache delegates during Load

---
 .../util-core/src/main/scala/sbt/internal/util/Util.scala | 7 +++++++
 main/src/main/scala/sbt/internal/Load.scala               | 8 ++++++--
 2 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/internal/util-core/src/main/scala/sbt/internal/util/Util.scala b/internal/util-core/src/main/scala/sbt/internal/util/Util.scala
index 028cd79a2..1ba2156f7 100644
--- a/internal/util-core/src/main/scala/sbt/internal/util/Util.scala
+++ b/internal/util-core/src/main/scala/sbt/internal/util/Util.scala
@@ -10,6 +10,8 @@ package sbt.internal.util
 
 import java.util.Locale
 
+import scala.collection.concurrent.TrieMap
+
 object Util {
   def makeList[T](size: Int, value: T): List[T] = List.fill(size)(value)
 
@@ -71,4 +73,9 @@ object Util {
   extension [A](value: A) {
     def some: Option[A] = (Some(value): Option[A])
   }
+
+  private[sbt] def withCaching[A1, A2](f: A1 => A2): A1 => A2 = {
+    val cache = TrieMap.empty[A1, A2]
+    x => cache.getOrElseUpdate(x, f(x))
+  }
 }
diff --git a/main/src/main/scala/sbt/internal/Load.scala b/main/src/main/scala/sbt/internal/Load.scala
index 7cf3bb2c2..d010d233f 100755
--- a/main/src/main/scala/sbt/internal/Load.scala
+++ b/main/src/main/scala/sbt/internal/Load.scala
@@ -35,6 +35,7 @@ import java.net.URI
 import java.nio.file.{ Path, Paths }
 import scala.annotation.tailrec
 import scala.collection.mutable
+import sbt.internal.util.Util
 
 private[sbt] object Load {
   // note that there is State passed in but not pulled out
@@ -266,11 +267,14 @@ private[sbt] object Load {
     }
     val projects = loaded.units
     lazy val rootEval = lazyEval(loaded.units(loaded.root).unit)
+    val settings0 = timed("Load.apply: buildConfigurations", log) {
+      buildConfigurations(loaded, getRootProject(projects), config.injectSettings)
+    }
     val settings = timed("Load.apply: finalTransforms", log) {
-      finalTransforms(buildConfigurations(loaded, getRootProject(projects), config.injectSettings))
+      finalTransforms(settings0)
     }
     val delegates = timed("Load.apply: config.delegates", log) {
-      config.delegates(loaded)
+      Util.withCaching(config.delegates(loaded))
     }
     val (cMap, data) = timed("Load.apply: Def.make(settings)...", log) {
       // When settings.size is 100000, Def.make takes around 10s.