From 9c611ce9cce36b2618361f3fccd73cd8aa6dcf5f Mon Sep 17 00:00:00 2001
From: Evan Loriot <12630925+evanloriot@users.noreply.github.com>
Date: Sat, 15 Nov 2025 11:14:55 -0800
Subject: [PATCH 1/2] Fix shutdown hooks for JUnit5 for JDK24+. Previously, all
 tests would exit with System.exit or Runtime.exit was called because the
 shutdown hook was not removed at test teardown.

---
 .../junit5/JUnit5Runner.java                  | 16 +++----
 .../junit5/NullSystemExitToggle.java          | 23 +++++++++-
 .../junit5/NullSystemExitToggleTest.java      | 45 +++++++++++++++++++
 3 files changed, 71 insertions(+), 13 deletions(-)
 create mode 100644 java/test/com/github/bazel_contrib/contrib_rules_jvm/junit5/NullSystemExitToggleTest.java

diff --git a/java/src/com/github/bazel_contrib/contrib_rules_jvm/junit5/JUnit5Runner.java b/java/src/com/github/bazel_contrib/contrib_rules_jvm/junit5/JUnit5Runner.java
index 55a1d390..29047c04 100644
--- a/java/src/com/github/bazel_contrib/contrib_rules_jvm/junit5/JUnit5Runner.java
+++ b/java/src/com/github/bazel_contrib/contrib_rules_jvm/junit5/JUnit5Runner.java
@@ -87,19 +87,13 @@ private static SystemExitToggle getSystemExitToggle() {
         System.err.println("Failed to load Java 17 system exit override: " + e.getMessage());
       }
 
-      // Install a shutdown hook so people can track down what went wrong
-      // if a test calls `System.exit`
-      Thread shutdownHook = SystemExitDetectingShutdownHook.newShutdownHook(System.err);
-      Runtime.getRuntime().addShutdownHook(shutdownHook);
-
       // Fall through
-    }
+      System.err.println(
+          "Unable to create a mechanism to prevent `System.exit` being called. "
+              + "Tests may cause `bazel test` to exit prematurely.");
 
-    System.err.println(
-        "Unable to create a mechanism to prevent `System.exit` being called. "
-            + "Tests may cause `bazel test` to exit prematurely.");
-
-    return new NullSystemExitToggle();
+      return new NullSystemExitToggle();
+    }
   }
 
   private static void detectJUnit5Classes() {
diff --git a/java/src/com/github/bazel_contrib/contrib_rules_jvm/junit5/NullSystemExitToggle.java b/java/src/com/github/bazel_contrib/contrib_rules_jvm/junit5/NullSystemExitToggle.java
index f088b659..34b85af9 100644
--- a/java/src/com/github/bazel_contrib/contrib_rules_jvm/junit5/NullSystemExitToggle.java
+++ b/java/src/com/github/bazel_contrib/contrib_rules_jvm/junit5/NullSystemExitToggle.java
@@ -1,13 +1,32 @@
 package com.github.bazel_contrib.contrib_rules_jvm.junit5;
 
+import java.util.Optional;
+
 public class NullSystemExitToggle implements SystemExitToggle {
+
+  private Optional<Thread> shutdownHook;
+
+  public NullSystemExitToggle() {
+    this.shutdownHook = Optional.empty();
+  }
+
   @Override
   public void prevent() {
-    // No-op
+    if (!shutdownHook.isEmpty()) {
+      throw new RuntimeException("SystemExitDetectingShutdownHook already added");
+    }
+    // Install a shutdown hook so people can track down what went wrong
+    // if a test calls `System.exit`
+    Thread shutdownHook = SystemExitDetectingShutdownHook.newShutdownHook(System.err);
+    this.shutdownHook = Optional.of(shutdownHook);
+    Runtime.getRuntime().addShutdownHook(shutdownHook);
   }
 
   @Override
   public void allow() {
-    // No-op
+    if (shutdownHook.isEmpty()) {
+      throw new RuntimeException("SystemExitDetectingShutdownHook never added");
+    }
+    Runtime.getRuntime().removeShutdownHook(shutdownHook.get());
   }
 }
diff --git a/java/test/com/github/bazel_contrib/contrib_rules_jvm/junit5/NullSystemExitToggleTest.java b/java/test/com/github/bazel_contrib/contrib_rules_jvm/junit5/NullSystemExitToggleTest.java
new file mode 100644
index 00000000..5e150903
--- /dev/null
+++ b/java/test/com/github/bazel_contrib/contrib_rules_jvm/junit5/NullSystemExitToggleTest.java
@@ -0,0 +1,45 @@
+package com.github.bazel_contrib.contrib_rules_jvm.junit5;
+
+import static org.junit.jupiter.api.Assertions.assertThrows;
+
+import org.junit.jupiter.api.Test;
+
+public class NullSystemExitToggleTest {
+
+  @Test
+  public void prevent_alreadyPrevented_throwsRuntimeException() {
+    // Arrange.
+    NullSystemExitToggle toggle = new NullSystemExitToggle();
+
+    // Act and Assert.
+    toggle.prevent();
+    assertThrows(RuntimeException.class, () -> toggle.prevent());
+
+    // Cleanup.
+    toggle.allow();
+  }
+
+
+  @Test
+  public void allow_alreadyAllowed_throwsRuntimeException() {
+    // Arrange.
+    NullSystemExitToggle toggle = new NullSystemExitToggle();
+
+    // Act and Assert.
+    assertThrows(RuntimeException.class, () -> toggle.allow());
+  }
+
+  @Test
+  public void normalFlow_success() {
+    // Arrange.
+    NullSystemExitToggle toggle = new NullSystemExitToggle();
+
+    // Act and (implicit) Assert.
+    try {
+      toggle.prevent();
+    } finally {
+      toggle.allow();
+    }
+  }
+
+}

From 83942ab12e8e0e5aab77850aac5afcf066613a3e Mon Sep 17 00:00:00 2001
From: Evan Loriot <12630925+evanloriot@users.noreply.github.com>
Date: Tue, 18 Nov 2025 21:33:30 -0800
Subject: [PATCH 2/2] fix formatting

---
 .../contrib_rules_jvm/junit5/NullSystemExitToggleTest.java      | 2 --
 1 file changed, 2 deletions(-)

diff --git a/java/test/com/github/bazel_contrib/contrib_rules_jvm/junit5/NullSystemExitToggleTest.java b/java/test/com/github/bazel_contrib/contrib_rules_jvm/junit5/NullSystemExitToggleTest.java
index 5e150903..f9e00969 100644
--- a/java/test/com/github/bazel_contrib/contrib_rules_jvm/junit5/NullSystemExitToggleTest.java
+++ b/java/test/com/github/bazel_contrib/contrib_rules_jvm/junit5/NullSystemExitToggleTest.java
@@ -19,7 +19,6 @@ public void prevent_alreadyPrevented_throwsRuntimeException() {
     toggle.allow();
   }
 
-
   @Test
   public void allow_alreadyAllowed_throwsRuntimeException() {
     // Arrange.
@@ -41,5 +40,4 @@ public void normalFlow_success() {
       toggle.allow();
     }
   }
-
 }