From 79c60ca4c10d85a6fd18f8e5d35dc39141d07adf Mon Sep 17 00:00:00 2001
From: Pegasus <42954461+leonace924@users.noreply.github.com>
Date: Thu, 15 Jan 2026 22:52:38 -0500
Subject: [PATCH] [2.x] fix: Allow dependencyTree to run despite eviction
 errors (#8554)

**Problem**
When binary compatibility eviction errors occur, users cannot run
`dependencyTree` to debug the dependency conflict because it fails
with the same eviction error.

**Solution**
Set `evictionErrorLevel` and `assumedEvictionErrorLevel` to `Level.Warn`
for the `dependencyTreeIgnoreMissingUpdate` task, allowing the dependency
tree to be displayed even when eviction errors are present.

Fixes #7255
---
 .../sbt/plugins/DependencyTreeSettings.scala  |  6 ++++--
 .../dependency-graph/eviction-error/build.sbt | 19 +++++++++++++++++++
 .../dependency-graph/eviction-error/test      |  2 ++
 3 files changed, 25 insertions(+), 2 deletions(-)
 create mode 100644 sbt-app/src/sbt-test/dependency-graph/eviction-error/build.sbt
 create mode 100644 sbt-app/src/sbt-test/dependency-graph/eviction-error/test

diff --git a/main/src/main/scala/sbt/plugins/DependencyTreeSettings.scala b/main/src/main/scala/sbt/plugins/DependencyTreeSettings.scala
index ed47af3af..4661f5fdb 100644
--- a/main/src/main/scala/sbt/plugins/DependencyTreeSettings.scala
+++ b/main/src/main/scala/sbt/plugins/DependencyTreeSettings.scala
@@ -24,7 +24,7 @@ import sbt.internal.util.complete.DefaultParsers.*
 import sbt.io.IO
 import sbt.io.syntax.*
 import sbt.librarymanagement.*
-import sbt.util.Logger
+import sbt.util.{ Level, Logger }
 import scala.Console
 
 private[sbt] object DependencyTreeSettings:
@@ -123,9 +123,11 @@ OPTIONS
         val is = new IvySbt((dependencyTreeIgnoreMissingUpdate / ivyConfiguration).value)
         new is.Module(moduleSettings.value)
       },
-      // don't fail on missing dependencies
+      // don't fail on missing dependencies or eviction errors
       dependencyTreeIgnoreMissingUpdate / updateConfiguration := updateConfiguration.value
         .withMissingOk(true),
+      dependencyTreeIgnoreMissingUpdate / evictionErrorLevel := Level.Warn,
+      dependencyTreeIgnoreMissingUpdate / assumedEvictionErrorLevel := Level.Warn,
       dependencyTreeIgnoreMissingUpdate := Def.uncached {
         // inTask will make sure the new definition will pick up `ivyModule/updateConfiguration in ignoreMissingUpdate`
         Project.inTask(dependencyTreeIgnoreMissingUpdate, Classpaths.updateTask).value
diff --git a/sbt-app/src/sbt-test/dependency-graph/eviction-error/build.sbt b/sbt-app/src/sbt-test/dependency-graph/eviction-error/build.sbt
new file mode 100644
index 000000000..e5f40f777
--- /dev/null
+++ b/sbt-app/src/sbt-test/dependency-graph/eviction-error/build.sbt
@@ -0,0 +1,19 @@
+// Test that dependencyTree works despite eviction errors
+// This demonstrates the fix for https://github.com/sbt/sbt/issues/7255
+
+ThisBuild / scalaVersion := "2.13.12"
+ThisBuild / csrCacheDirectory := (ThisBuild / baseDirectory).value / "coursier-cache"
+
+// Create a binary incompatible eviction using real Maven dependencies:
+// - scalacheck 1.14.3 depends on test-interface 1.0
+// - scalacheck 1.15.4 depends on test-interface 1.0
+// - We force an eviction by depending on incompatible versions
+// Or simpler: use libraries with known eviction issues
+
+// cats-effect 2.x and 3.x are binary incompatible (early-semver)
+// fs2 2.5.x depends on cats-effect 2.x
+// We also add cats-effect 3.x directly to force eviction
+libraryDependencies ++= Seq(
+  "co.fs2" %% "fs2-core" % "2.5.11",        // depends on cats-effect 2.x
+  "org.typelevel" %% "cats-effect" % "3.3.0" // cats-effect 3.x (incompatible)
+)
diff --git a/sbt-app/src/sbt-test/dependency-graph/eviction-error/test b/sbt-app/src/sbt-test/dependency-graph/eviction-error/test
new file mode 100644
index 000000000..00910adff
--- /dev/null
+++ b/sbt-app/src/sbt-test/dependency-graph/eviction-error/test
@@ -0,0 +1,2 @@
+# Test that dependencyTree works despite eviction errors (issue #7255)
+> dependencyTree