[9.1] [ML] Perform query field validation for rerank task type (#137219)

docs/changelog/137219.yaml

@@ -0,0 +1,5 @@
+pr: 137219
+summary: Perform query field validation for rerank task type
+area: Machine Learning
+type: bug
+issues: []

x-pack/plugin/inference/src/main/java/org/elasticsearch/xpack/inference/services/SenderService.java

@@ -90,6 +90,11 @@ private static InferenceInputs createInput(
             case RERANK -> {
                 ValidationException validationException = new ValidationException();
                 service.validateRerankParameters(returnDocuments, topN, validationException);
+
+                if (query == null) {
+                    validationException.addValidationError("Rerank task type requires a non-null query field");
+                }
+
                 if (validationException.validationErrors().isEmpty() == false) {
                     throw validationException;
                 }

x-pack/plugin/inference/src/test/java/org/elasticsearch/xpack/inference/services/SenderServiceTests.java

@@ -21,8 +21,10 @@
 import org.elasticsearch.inference.TaskType;
 import org.elasticsearch.test.ESTestCase;
 import org.elasticsearch.threadpool.ThreadPool;
+import org.elasticsearch.xpack.inference.external.http.sender.ChatCompletionInput;
 import org.elasticsearch.xpack.inference.external.http.sender.HttpRequestSender;
 import org.elasticsearch.xpack.inference.external.http.sender.InferenceInputs;
+import org.elasticsearch.xpack.inference.external.http.sender.QueryAndDocsInputs;
 import org.elasticsearch.xpack.inference.external.http.sender.Sender;
 import org.elasticsearch.xpack.inference.external.http.sender.UnifiedChatInput;
 import org.junit.After;
@@ -34,9 +36,12 @@
 import java.util.List;
 import java.util.Map;
 import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicReference;
 
 import static org.elasticsearch.xpack.inference.Utils.inferenceUtilityPool;
 import static org.elasticsearch.xpack.inference.services.ServiceComponentsTests.createWithEmptySettings;
+import static org.hamcrest.Matchers.containsString;
+import static org.hamcrest.Matchers.is;
 import static org.mockito.Mockito.mock;
 import static org.mockito.Mockito.times;
 import static org.mockito.Mockito.verify;
@@ -101,7 +106,113 @@ public void testStart_CallingStartTwiceKeepsSameSenderReference() throws IOExcep
         verifyNoMoreInteractions(sender);
     }
 
-    private static final class TestSenderService extends SenderService {
+    public void testReturnsValidationException_WhenQueryIsNullForRerankTaskType() throws IOException {
+        var sender = mock(Sender.class);
+
+        var factory = mock(HttpRequestSender.Factory.class);
+        when(factory.createSender()).thenReturn(sender);
+
+        try (var testService = new TestSenderService(factory, createWithEmptySettings(threadPool))) {
+            var model = mock(Model.class);
+            when(model.getTaskType()).thenReturn(TaskType.RERANK);
+
+            var exception = expectThrows(
+                ValidationException.class,
+                () -> testService.infer(
+                    model,
+                    null,
+                    null,
+                    null,
+                    List.of("test input"),
+                    false,
+                    Map.of(),
+                    InputType.SEARCH,
+                    null,
+                    new PlainActionFuture<>()
+                )
+            );
+
+            assertThat(exception.getMessage(), containsString("Rerank task type requires a non-null query field"));
+        }
+    }
+
+    public void testInferSucceeds_WhenQueryIsDefinedForRerankTaskType() throws IOException {
+        var sender = mock(Sender.class);
+
+        var factory = mock(HttpRequestSender.Factory.class);
+        when(factory.createSender()).thenReturn(sender);
+
+        var queryString = "a query";
+        var testInput = "test input";
+        var doInferCalled = new AtomicReference<>(false);
+
+        var testService = new TestSenderService(factory, createWithEmptySettings(threadPool)) {
+            @Override
+            protected void doInfer(
+                Model model,
+                InferenceInputs inputs,
+                Map<String, Object> taskSettings,
+                TimeValue timeout,
+                ActionListener<InferenceServiceResults> listener
+            ) {
+                var queryDocs = inputs.castTo(QueryAndDocsInputs.class);
+                assertThat(queryDocs.getQuery(), is(queryString));
+                assertThat(queryDocs.getChunks(), is(List.of(testInput)));
+                doInferCalled.set(true);
+                listener.onResponse(mock(InferenceServiceResults.class));
+            }
+        };
+
+        try (testService) {
+            var model = mock(Model.class);
+            when(model.getTaskType()).thenReturn(TaskType.RERANK);
+
+            PlainActionFuture<InferenceServiceResults> listener = new PlainActionFuture<>();
+
+            testService.infer(model, queryString, null, null, List.of(testInput), false, Map.of(), null, null, listener);
+            assertNotNull(listener.actionGet(TIMEOUT));
+            assertTrue(doInferCalled.get());
+        }
+    }
+
+    public void testInferSucceeds_WhenQueryIsNotDefinedForCompletionTaskType() throws IOException {
+        var sender = mock(Sender.class);
+
+        var factory = mock(HttpRequestSender.Factory.class);
+        when(factory.createSender()).thenReturn(sender);
+
+        var testInput = "test input";
+        var doInferCalled = new AtomicReference<>(false);
+
+        var testService = new TestSenderService(factory, createWithEmptySettings(threadPool)) {
+            @Override
+            protected void doInfer(
+                Model model,
+                InferenceInputs inputs,
+                Map<String, Object> taskSettings,
+                TimeValue timeout,
+                ActionListener<InferenceServiceResults> listener
+            ) {
+                var castedInput = inputs.castTo(ChatCompletionInput.class);
+                assertThat(castedInput.getInputs(), is(List.of(testInput)));
+                doInferCalled.set(true);
+                listener.onResponse(mock(InferenceServiceResults.class));
+            }
+        };
+
+        try (testService) {
+            var model = mock(Model.class);
+            when(model.getTaskType()).thenReturn(TaskType.COMPLETION);
+
+            PlainActionFuture<InferenceServiceResults> listener = new PlainActionFuture<>();
+
+            testService.infer(model, null, null, null, List.of(testInput), false, Map.of(), null, null, listener);
+            assertNotNull(listener.actionGet(TIMEOUT));
+            assertTrue(doInferCalled.get());
+        }
+    }
+
+    private static class TestSenderService extends SenderService {
         TestSenderService(HttpRequestSender.Factory factory, ServiceComponents serviceComponents) {
             super(factory, serviceComponents);
         }