From f11dd007cd8e231a43ed9178d6b881f13b77e0e6 Mon Sep 17 00:00:00 2001
From: Nitish Agarwal <1592163+nitishagar@users.noreply.github.com>
Date: Fri, 26 Dec 2025 13:26:02 +0530
Subject: [PATCH] Fix UnsupportedOperationException when merging
 ActivityOptions with immutable context propagators

The mergeActivityOptions method was calling addAll() directly on the existing
contextPropagators list, which fails when the list is immutable (e.g., created
with List.of() or Collections.emptyList()).

This fix creates a new ArrayList that combines both lists instead of modifying
the existing one.

Fixes #2482
---
 .../io/temporal/activity/ActivityOptions.java |  5 +-
 .../activity/ActivityOptionsTest.java         | 67 +++++++++++++++++++
 2 files changed, 71 insertions(+), 1 deletion(-)

diff --git a/temporal-sdk/src/main/java/io/temporal/activity/ActivityOptions.java b/temporal-sdk/src/main/java/io/temporal/activity/ActivityOptions.java
index 69032d1f7..f67a4beed 100644
--- a/temporal-sdk/src/main/java/io/temporal/activity/ActivityOptions.java
+++ b/temporal-sdk/src/main/java/io/temporal/activity/ActivityOptions.java
@@ -6,6 +6,7 @@
 import io.temporal.common.context.ContextPropagator;
 import io.temporal.failure.CanceledFailure;
 import java.time.Duration;
+import java.util.ArrayList;
 import java.util.List;
 
 /** Options used to configure how an activity is invoked. */
@@ -282,7 +283,9 @@ public Builder mergeActivityOptions(ActivityOptions override) {
       if (this.contextPropagators == null) {
         this.contextPropagators = override.contextPropagators;
       } else if (override.contextPropagators != null) {
-        this.contextPropagators.addAll(override.contextPropagators);
+        List<ContextPropagator> merged = new ArrayList<>(this.contextPropagators);
+        merged.addAll(override.contextPropagators);
+        this.contextPropagators = merged;
       }
       if (override.versioningIntent != VersioningIntent.VERSIONING_INTENT_UNSPECIFIED) {
         this.versioningIntent = override.versioningIntent;
diff --git a/temporal-sdk/src/test/java/io/temporal/activity/ActivityOptionsTest.java b/temporal-sdk/src/test/java/io/temporal/activity/ActivityOptionsTest.java
index 26f8cc910..fb51ce7c8 100644
--- a/temporal-sdk/src/test/java/io/temporal/activity/ActivityOptionsTest.java
+++ b/temporal-sdk/src/test/java/io/temporal/activity/ActivityOptionsTest.java
@@ -2,13 +2,17 @@
 
 import static org.junit.Assert.*;
 
+import io.temporal.api.common.v1.Payload;
 import io.temporal.common.MethodRetry;
 import io.temporal.common.RetryOptions;
+import io.temporal.common.context.ContextPropagator;
 import io.temporal.testing.TestActivityEnvironment;
 import io.temporal.workflow.shared.TestActivities.TestActivity;
 import io.temporal.workflow.shared.TestActivities.TestActivityImpl;
 import java.lang.reflect.Method;
 import java.time.Duration;
+import java.util.Collections;
+import java.util.List;
 import java.util.Map;
 import org.junit.*;
 import org.junit.rules.Timeout;
@@ -62,6 +66,69 @@ public void testActivityOptionsMerge() {
     Assert.assertEquals(methodOps1, merged);
   }
 
+  @Test
+  public void testActivityOptionsMergeWithImmutableContextPropagators() {
+    // Local class to avoid code duplication
+    class TestContextPropagator implements ContextPropagator {
+      private final String name;
+
+      TestContextPropagator(String name) {
+        this.name = name;
+      }
+
+      @Override
+      public String getName() {
+        return name;
+      }
+
+      @Override
+      public Map<String, Payload> serializeContext(Object context) {
+        return Collections.emptyMap();
+      }
+
+      @Override
+      public Object deserializeContext(Map<String, Payload> context) {
+        return null;
+      }
+
+      @Override
+      public Object getCurrentContext() {
+        return null;
+      }
+
+      @Override
+      public void setCurrentContext(Object context) {}
+    }
+
+    ContextPropagator propagator1 = new TestContextPropagator("propagator1");
+    ContextPropagator propagator2 = new TestContextPropagator("propagator2");
+
+    // Create options with immutable singleton lists
+    // This tests the fix for https://github.com/temporalio/sdk-java/issues/2482
+    ActivityOptions options1 =
+        ActivityOptions.newBuilder()
+            .setStartToCloseTimeout(Duration.ofSeconds(1))
+            .setContextPropagators(Collections.singletonList(propagator1))
+            .build();
+
+    ActivityOptions options2 =
+        ActivityOptions.newBuilder()
+            .setStartToCloseTimeout(Duration.ofSeconds(2))
+            .setContextPropagators(Collections.singletonList(propagator2))
+            .build();
+
+    // Merging should not throw UnsupportedOperationException
+    ActivityOptions merged =
+        ActivityOptions.newBuilder(options1).mergeActivityOptions(options2).build();
+
+    // Verify both context propagators are present in the merged result
+    List<ContextPropagator> mergedPropagators = merged.getContextPropagators();
+    assertNotNull(mergedPropagators);
+    assertEquals(2, mergedPropagators.size());
+    assertEquals("propagator1", mergedPropagators.get(0).getName());
+    assertEquals("propagator2", mergedPropagators.get(1).getName());
+  }
+
   @Test
   public void testActivityOptionsDefaultInstance() {
     testEnv.registerActivitiesImplementations(new TestActivityImpl());