From 001fbf8e699589dc849cb517cc2cdbb152c69efe Mon Sep 17 00:00:00 2001
From: Eugene Yokota <eed3si9n@gmail.com>
Date: Mon, 1 Jun 2026 06:36:19 -0400
Subject: [PATCH] [2.0.x] fix: Avoid updateFull

**Problem**
updateFull is called in no-op compile.

**Solution**
Avoid it for the default dependency mode.
---
 main/src/main/scala/sbt/Defaults.scala        | 84 +++++++++++++------
 .../scala/sbt/internal/ClasspathImpl.scala    |  2 +-
 2 files changed, 59 insertions(+), 27 deletions(-)

diff --git a/main/src/main/scala/sbt/Defaults.scala b/main/src/main/scala/sbt/Defaults.scala
index 4223c82ec..fb73d8138 100644
--- a/main/src/main/scala/sbt/Defaults.scala
+++ b/main/src/main/scala/sbt/Defaults.scala
@@ -2737,17 +2737,31 @@ object Classpaths {
           dependencyMode.value match
             case DependencyMode.Transitive =>
               Def.task { dependencyClasspath.value }
-            case mode =>
+            case DependencyMode.Direct =>
               Def.task {
                 val internalFiltered = ClasspathImpl.filterInternalByMode(
-                  mode,
+                  DependencyMode.Direct,
                   thisProjectRef.value,
                   settingsData.value,
                   buildDependencies.value,
                   internalDependencyClasspath.value,
                 )
-                val externalFiltered = ClasspathImpl.filterByDependencyMode(
-                  mode,
+                val externalFiltered = ClasspathImpl.filterByDirectDeps(
+                  allDependencies.value,
+                  externalDependencyClasspath.value,
+                )
+                internalFiltered ++ externalFiltered
+              }
+            case DependencyMode.PlusOne =>
+              Def.task {
+                val internalFiltered = ClasspathImpl.filterInternalByMode(
+                  DependencyMode.PlusOne,
+                  thisProjectRef.value,
+                  settingsData.value,
+                  buildDependencies.value,
+                  internalDependencyClasspath.value,
+                )
+                val externalFiltered = ClasspathImpl.filterByPlusOne(
                   allDependencies.value,
                   projectID.value,
                   classpathConfiguration.value,
@@ -2815,28 +2829,46 @@ object Classpaths {
       // Note: invoking this task from shell would block indefinitely because it will
       // wait for the upstream compilation to start.
       dependencyPicklePath := Def.uncached {
-        // This is a conditional task. Do not refactor.
-        if (incOptions.value.pipelining) {
-          val mode = dependencyMode.value
-          val internalFiltered = ClasspathImpl.filterInternalByMode(
-            mode,
-            thisProjectRef.value,
-            settingsData.value,
-            buildDependencies.value,
-            internalDependencyPicklePath.value,
-          )
-          val externalFiltered = ClasspathImpl.filterByDependencyMode(
-            mode,
-            allDependencies.value,
-            projectID.value,
-            classpathConfiguration.value,
-            updateFull.value,
-            externalDependencyClasspath.value,
-          )
-          internalFiltered ++ externalFiltered
-        } else {
-          filteredDependencyClasspath.value
-        }
+        Def.taskDyn {
+          (incOptions.value.pipelining, dependencyMode.value) match
+            case (false, _) =>
+              Def.task { filteredDependencyClasspath.value }
+            case (true, DependencyMode.Transitive) =>
+              Def.task { dependencyClasspath.value }
+            case (true, DependencyMode.Direct) =>
+              Def.task {
+                val internalFiltered = ClasspathImpl.filterInternalByMode(
+                  DependencyMode.Direct,
+                  thisProjectRef.value,
+                  settingsData.value,
+                  buildDependencies.value,
+                  internalDependencyClasspath.value,
+                )
+                val externalFiltered = ClasspathImpl.filterByDirectDeps(
+                  allDependencies.value,
+                  externalDependencyClasspath.value,
+                )
+                internalFiltered ++ externalFiltered
+              }
+            case (true, DependencyMode.PlusOne) =>
+              Def.task {
+                val internalFiltered = ClasspathImpl.filterInternalByMode(
+                  DependencyMode.PlusOne,
+                  thisProjectRef.value,
+                  settingsData.value,
+                  buildDependencies.value,
+                  internalDependencyClasspath.value,
+                )
+                val externalFiltered = ClasspathImpl.filterByPlusOne(
+                  allDependencies.value,
+                  projectID.value,
+                  classpathConfiguration.value,
+                  updateFull.value,
+                  externalDependencyClasspath.value,
+                )
+                internalFiltered ++ externalFiltered
+              }
+        }.value
       },
       internalDependencyPicklePath := ClasspathImpl.internalDependencyPicklePathTask.value,
       exportedPickles := ClasspathImpl.exportedPicklesTask.value,
diff --git a/main/src/main/scala/sbt/internal/ClasspathImpl.scala b/main/src/main/scala/sbt/internal/ClasspathImpl.scala
index 9bcdf3a1a..d5dbeeb0a 100644
--- a/main/src/main/scala/sbt/internal/ClasspathImpl.scala
+++ b/main/src/main/scala/sbt/internal/ClasspathImpl.scala
@@ -577,7 +577,7 @@ private[sbt] object ClasspathImpl {
   ): Classpath =
     mode match
       case DependencyMode.Transitive => internalCp
-      case _ =>
+      case _                         =>
         val allowed = allowedInternalKeys(mode, projectRef, data, deps)
         internalCp.filter: entry =>
           entry.get(Keys.moduleIDStr) match