fix(batch): avoid NPE in TaskHandle.POISON#toString

https://open.spotify.com/track/5XcZRgJv3zMhTqCyESjQrF?si=53697170efd34e2a

Author: bevzzz

src/main/java/io/weaviate/client6/v1/api/collections/batch/TaskHandle.java

@@ -83,8 +83,8 @@ private TaskHandle() {
   }
 
   /**
-   * Creates a new task containing the same data as this task and {@link retries}
-   * counter incremented by 1. The {@link acked} and {@link result} futures
+   * Creates a new task containing the same data as this task and {@link #retries}
+   * counter incremented by 1. The {@link #acked} and {@link #result} futures
    * are not copied to the returned task.
    *
    * @return Task handle.
@@ -163,14 +163,17 @@ public CompletableFuture<Result> result() {
    * Number of times this task has been retried. Since {@link TaskHandle} is
    * immutable, this value does not change, but retrying a task via
    * {@link BatchContext#retry} is reflected in the returned handle's
-   * {@link #timesRetried}.
+   * timesRetried.
    */
   public int timesRetried() {
     return retries;
   }
 
   @Override
   public String toString() {
+    if (this == POISON) {
+      return "TaskHandle<POISON>";
+    }
     return "TaskHandle<id=%s, retried=%d, created=%s>".formatted(id(), retries, createdAt);
   }
 }

src/test/java/io/weaviate/client6/v1/api/collections/batch/TaskHandleTest.java

@@ -33,7 +33,7 @@ public class TaskHandleTest {
           CollectionHandleDefaults.of(CollectionHandleDefaults.none()));
 
   @Test
-  public void testTaskHandle_WeaviateObject_success() {
+  public void test_newTaskHandle_WeaviateObject_success() {
     TaskHandle taskHandle = new TaskHandle(OBJECT, OBJECT_PROTO);
 
     Assertions.assertThat(taskHandle)
@@ -58,7 +58,7 @@ public void testTaskHandle_WeaviateObject_success() {
   }
 
   @Test
-  public void testTaskHandle_WeaviateObject_error() {
+  public void test_newTaskHandle_WeaviateObject_error() {
     TaskHandle taskHandle = new TaskHandle(OBJECT, OBJECT_PROTO);
 
     Assertions.assertThat(taskHandle)
@@ -83,7 +83,7 @@ public void testTaskHandle_WeaviateObject_error() {
   }
 
   @Test
-  public void testTaskHandle_BatchReference_success() {
+  public void test_newTaskHandle_BatchReference_success() {
     TaskHandle taskHandle = new TaskHandle(REFERENCE, REFERENCE_PROTO);
 
     Assertions.assertThat(taskHandle)
@@ -108,7 +108,7 @@ public void testTaskHandle_BatchReference_success() {
   }
 
   @Test
-  public void testTaskHandle_BatchReference_error() {
+  public void test_newTaskHandle_BatchReference_error() {
     TaskHandle taskHandle = new TaskHandle(REFERENCE, REFERENCE_PROTO);
 
     Assertions.assertThat(taskHandle)
@@ -133,7 +133,7 @@ public void testTaskHandle_BatchReference_error() {
   }
 
   @Test
-  public void testTaskHandle_retry() {
+  public void test_retry() {
     TaskHandle taskHandle = new TaskHandle(OBJECT, OBJECT_PROTO);
     Assertions.assertThat(taskHandle).returns(0, TaskHandle::timesRetried);
 
@@ -147,6 +147,12 @@ public void testTaskHandle_retry() {
         .extracting(TaskHandle::data).isEqualTo(taskHandle.data());
   }
 
+  @Test
+  public void test_toString_POISON() {
+    Assertions.assertThat(TaskHandle.POISON.toString())
+        .isEqualTo("TaskHandle<POISON>");
+  }
+
   private void assertAcked(TaskHandle taskHandle, boolean expect) {
     Assertions.assertThat(taskHandle)
         .extracting(TaskHandle::isAcked)