fix: use explicit JSON merge patch type in merge patch operations

operator-framework-core/src/main/java/io/javaoperatorsdk/operator/api/reconciler/ResourceOperations.java

@@ -751,7 +751,10 @@ public <R extends HasMetadata> R jsonMergePatch(R desired) {
    * @return the patched resource as returned by the API server
    */
   public <R extends HasMetadata> R jsonMergePatch(R desired, Options options) {
-    return resourcePatch(desired, r -> context.getClient().resource(r).patch(), options);
+    return resourcePatch(
+        desired,
+        r -> context.getClient().resource(r).patch(PatchContext.of(PatchType.JSON_MERGE)),
+        options);
   }
 
   /**
@@ -767,7 +770,10 @@ public <R extends HasMetadata> R jsonMergePatch(R desired, Options options) {
   public <R extends HasMetadata> R jsonMergePatch(
       R desired, InformerEventSource<R, P> informerEventSource, Options options) {
     return resourcePatch(
-        desired, r -> context.getClient().resource(r).patch(), informerEventSource, options);
+        desired,
+        r -> context.getClient().resource(r).patch(PatchContext.of(PatchType.JSON_MERGE)),
+        informerEventSource,
+        options);
   }
 
   /**
@@ -838,7 +844,7 @@ public P jsonMergePatchPrimary(P resource) {
   public P jsonMergePatchPrimary(P resource, Options options) {
     return resourcePatch(
         resource,
-        r -> context.getClient().resource(r).patch(),
+        r -> context.getClient().resource(r).patch(PatchContext.of(PatchType.JSON_MERGE)),
         context.eventSourceRetriever().getControllerEventSource(),
         options);
   }

operator-framework-core/src/test/java/io/javaoperatorsdk/operator/api/reconciler/ResourceOperationsTest.java

@@ -22,6 +22,7 @@
 
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
+import org.mockito.ArgumentCaptor;
 import org.mockito.stubbing.Answer;
 
 import io.fabric8.kubernetes.api.model.HasMetadata;
@@ -31,6 +32,7 @@
 import io.fabric8.kubernetes.client.dsl.NamespaceableResource;
 import io.fabric8.kubernetes.client.dsl.Resource;
 import io.fabric8.kubernetes.client.dsl.base.PatchContext;
+import io.fabric8.kubernetes.client.dsl.base.PatchType;
 import io.fabric8.kubernetes.client.utils.KubernetesSerialization;
 import io.javaoperatorsdk.operator.TestUtils;
 import io.javaoperatorsdk.operator.api.config.Cloner;
@@ -40,6 +42,7 @@
 import io.javaoperatorsdk.operator.processing.event.EventSourceRetriever;
 import io.javaoperatorsdk.operator.processing.event.source.EventSource;
 import io.javaoperatorsdk.operator.processing.event.source.controller.ControllerEventSource;
+import io.javaoperatorsdk.operator.processing.event.source.informer.InformerEventSource;
 import io.javaoperatorsdk.operator.processing.event.source.informer.ManagedInformerEventSource;
 import io.javaoperatorsdk.operator.sample.simple.TestCustomResource;
 
@@ -471,15 +474,20 @@ private TestCustomResource wireVerbMocks() {
     when(verbClientResource.patch(any(PatchContext.class))).thenReturn(updated);
 
     // both cache paths execute the update operation so the underlying client verb runs
-    Answer<Object> runOperation =
-        invocation -> ((UnaryOperator) invocation.getArgument(1)).apply(invocation.getArgument(0));
     when(verbEventSource.eventFilteringUpdateAndCacheResource(any(), any(UnaryOperator.class)))
-        .thenAnswer(runOperation);
+        .thenAnswer(runUpdateOperation());
     when(verbEventSource.updateAndCacheResource(any(), any(UnaryOperator.class)))
-        .thenAnswer(runOperation);
+        .thenAnswer(runUpdateOperation());
     return updated;
   }
 
+  /** Answer that executes the update operation passed to the caching methods of an event source. */
+  @SuppressWarnings("rawtypes")
+  private static Answer<Object> runUpdateOperation() {
+    return invocation ->
+        ((UnaryOperator) invocation.getArgument(1)).apply(invocation.getArgument(0));
+  }
+
   // ---- update -------------------------------------------------------------
 
   @Test
@@ -610,7 +618,7 @@ void createWithNullEventSourceFallsBackToForceFilter() {
   // ---- patch / status verbs ----------------------------------------------
 
   @Test
-  void jsonMergePatchCacheOnlyCallsClientPatch() {
+  void jsonMergePatchCacheOnlyCallsClientMergePatch() {
     var resource = TestUtils.testCustomResource1();
     var updated = wireVerbMocks();
 
@@ -620,7 +628,51 @@ void jsonMergePatchCacheOnlyCallsClientPatch() {
     assertThat(result).isSameAs(updated);
     verify(verbEventSource, times(1))
         .updateAndCacheResource(eq(resource), any(UnaryOperator.class));
-    verify(verbClientResource, times(1)).patch();
+    assertThat(capturedPatchType()).isEqualTo(PatchType.JSON_MERGE);
+  }
+
+  @Test
+  void jsonMergePatchWithEventSourceCallsClientMergePatch() {
+    var resource = TestUtils.testCustomResource1();
+    var updated = wireVerbMocks();
+    InformerEventSource<TestCustomResource, TestCustomResource> informerEventSource =
+        mock(InformerEventSource.class);
+    when(informerEventSource.updateAndCacheResource(any(), any(UnaryOperator.class)))
+        .thenAnswer(runUpdateOperation());
+
+    var result =
+        resourceOperations.jsonMergePatch(
+            resource, informerEventSource, ResourceOperations.Options.cacheOnly());
+
+    assertThat(result).isSameAs(updated);
+    assertThat(capturedPatchType()).isEqualTo(PatchType.JSON_MERGE);
+  }
+
+  @Test
+  void jsonMergePatchPrimaryCallsClientMergePatch() {
+    var resource = TestUtils.testCustomResource1();
+    var updated = wireVerbMocks();
+    when(controllerEventSource.updateAndCacheResource(any(), any(UnaryOperator.class)))
+        .thenAnswer(runUpdateOperation());
+
+    var result =
+        resourceOperations.jsonMergePatchPrimary(resource, ResourceOperations.Options.cacheOnly());
+
+    assertThat(result).isSameAs(updated);
+    assertThat(capturedPatchType()).isEqualTo(PatchType.JSON_MERGE);
+  }
+
+  /**
+   * Asserts that a merge patch operation went through Fabric8 with an explicit patch context and
+   * returns the used patch type. The no-context {@code patch()} must never be used for merge
+   * patches: it computes an RFC 6902 diff against the resource fetched from the server, which
+   * removes the fields missing from a partial resource.
+   */
+  private PatchType capturedPatchType() {
+    verify(verbClientResource, never()).patch();
+    var captor = ArgumentCaptor.forClass(PatchContext.class);
+    verify(verbClientResource, times(1)).patch(captor.capture());
+    return captor.getValue().getPatchType();
   }
 
   @Test

operator-framework/src/test/java/io/javaoperatorsdk/operator/baseapi/resourceoperations/ResourceOperationsIT.java

@@ -24,6 +24,8 @@
 import io.javaoperatorsdk.operator.baseapi.resourceoperations.ResourceOperationsReconciler.Operation;
 import io.javaoperatorsdk.operator.junit.LocallyRunOperatorExtension;
 
+import static io.javaoperatorsdk.operator.baseapi.resourceoperations.ResourceOperationsReconciler.LABEL_KEY;
+import static io.javaoperatorsdk.operator.baseapi.resourceoperations.ResourceOperationsReconciler.LABEL_VALUE;
 import static io.javaoperatorsdk.operator.baseapi.resourceoperations.ResourceOperationsReconciler.SPEC_MARKER;
 import static io.javaoperatorsdk.operator.baseapi.resourceoperations.ResourceOperationsReconciler.STATUS_VALUE;
 import static org.assertj.core.api.Assertions.assertThat;
@@ -86,6 +88,31 @@ void jsonMergePatch() {
     assertSpecOperation(Operation.JSON_MERGE_PATCH);
   }
 
+  /**
+   * A merge patch applied with a partial resource must only change what the partial resource
+   * contains; fields omitted from it - like the whole {@code spec} - have to survive on the server.
+   */
+  @Test
+  void jsonMergePatchWithPartialResourceKeepsOmittedFields() {
+    var operation = Operation.JSON_MERGE_PATCH_PARTIAL_METADATA;
+    runOperation(operation);
+
+    await()
+        .atMost(Duration.ofSeconds(30))
+        .untilAsserted(
+            () ->
+                assertThat(actual().getMetadata().getLabels())
+                    .as("the partial metadata merge patch should be applied")
+                    .containsEntry(LABEL_KEY, LABEL_VALUE));
+
+    assertThat(actual().getSpec())
+        .as("the spec omitted from the partial merge patch should not be removed")
+        .isNotNull()
+        .extracting(ResourceOperationsSpec::getValue)
+        .isEqualTo(INITIAL_SPEC_VALUE);
+    assertConvergesWithoutLooping(operation);
+  }
+
   @Test
   void jsonMergePatchStatus() {
     assertStatusOperation(Operation.JSON_MERGE_PATCH_STATUS);

operator-framework/src/test/java/io/javaoperatorsdk/operator/baseapi/resourceoperations/ResourceOperationsReconciler.java

@@ -15,6 +15,7 @@
  */
 package io.javaoperatorsdk.operator.baseapi.resourceoperations;
 
+import java.util.Map;
 import java.util.concurrent.atomic.AtomicInteger;
 
 import io.fabric8.kubernetes.api.model.ObjectMetaBuilder;
@@ -40,6 +41,8 @@ public class ResourceOperationsReconciler implements Reconciler<ResourceOperatio
 
   public static final String STATUS_VALUE = "reconciled";
   public static final String SPEC_MARKER = "applied";
+  public static final String LABEL_KEY = "resolved";
+  public static final String LABEL_VALUE = "true";
 
   public enum Operation {
     SSA,
@@ -49,6 +52,7 @@ public enum Operation {
     JSON_PATCH,
     JSON_PATCH_STATUS,
     JSON_MERGE_PATCH,
+    JSON_MERGE_PATCH_PARTIAL_METADATA,
     JSON_MERGE_PATCH_STATUS
   }
 
@@ -102,6 +106,18 @@ public UpdateControl<ResourceOperationsCustomResource> reconcile(
         markResource(resource);
         ops.jsonMergePatchPrimary(resource);
       }
+      // a partial resource, holding only the metadata to change: a merge patch must not touch the
+      // fields omitted from it (like spec)
+      case JSON_MERGE_PATCH_PARTIAL_METADATA -> {
+        ResourceOperationsCustomResource partial = new ResourceOperationsCustomResource();
+        partial.setMetadata(
+            new ObjectMetaBuilder()
+                .withName(resource.getMetadata().getName())
+                .withNamespace(resource.getMetadata().getNamespace())
+                .withLabels(Map.of(LABEL_KEY, LABEL_VALUE))
+                .build());
+        ops.jsonMergePatchPrimary(partial);
+      }
       case JSON_MERGE_PATCH_STATUS -> {
         resource.setStatus(new ResourceOperationsStatus().setValue(STATUS_VALUE));
         ops.jsonMergePatchPrimaryStatus(resource);