Feature: Allow changed operation IDs to be flagged as incompatible

core/src/main/java/org/openapitools/openapidiff/core/compare/OpenApiDiff.java

@@ -40,6 +40,7 @@ public class OpenApiDiff {
   private OAuthFlowDiff oAuthFlowDiff;
   private ExtensionsDiff extensionsDiff;
   private MetadataDiff metadataDiff;
+  private OperationIdDiff operationIdDiff;
   private final OpenAPI oldSpecOpenApi;
   private final OpenAPI newSpecOpenApi;
   private final OpenApiDiffOptions options;
@@ -93,6 +94,7 @@ private void initializeFields() {
     this.oAuthFlowDiff = new OAuthFlowDiff(this);
     this.extensionsDiff = new ExtensionsDiff(this);
     this.metadataDiff = new MetadataDiff(this);
+    this.operationIdDiff = new OperationIdDiff(this);
     this.deferredSchemaCache = new DeferredSchemaCache(this);
   }
 
@@ -270,6 +272,10 @@ public MetadataDiff getMetadataDiff() {
     return this.metadataDiff;
   }
 
+  public OperationIdDiff getOperationIdDiff() {
+    return this.operationIdDiff;
+  }
+
   public OpenAPI getOldSpecOpenApi() {
     return this.oldSpecOpenApi;
   }

core/src/main/java/org/openapitools/openapidiff/core/compare/OperationDiff.java

@@ -53,7 +53,7 @@ public DeferredChanged<ChangedOperation> diff(
     builder
         .with(
             openApiDiff
-                .getMetadataDiff()
+                .getOperationIdDiff()
                 .diff(oldOperation.getOperationId(), newOperation.getOperationId(), context))
         .ifPresent(changedOperation::setOperationId);
     changedOperation.setDeprecated(

core/src/main/java/org/openapitools/openapidiff/core/compare/OperationIdDiff.java

@@ -0,0 +1,19 @@
+package org.openapitools.openapidiff.core.compare;
+
+import static org.openapitools.openapidiff.core.utils.ChangedUtils.isChanged;
+
+import java.util.Optional;
+import org.openapitools.openapidiff.core.model.DiffContext;
+import org.openapitools.openapidiff.core.model.schema.ChangedOperationId;
+
+public class OperationIdDiff {
+  private final OpenApiDiff openApiDiff;
+
+  public OperationIdDiff(OpenApiDiff openApiDiff) {
+    this.openApiDiff = openApiDiff;
+  }
+
+  public Optional<ChangedOperationId> diff(String left, String right, DiffContext context) {
+    return isChanged(new ChangedOperationId(left, right, context));
+  }
+}

core/src/main/java/org/openapitools/openapidiff/core/model/BackwardIncompatibleProp.java

@@ -10,6 +10,7 @@ public enum BackwardIncompatibleProp {
   EXTENSION_CONTENT_TYPES_DECREASED("incompatible.extension.content.types.decreased", false),
   EXTENSION_CONTENT_TYPE_DELETED("incompatible.extension.content.type.%s.deleted", false),
   OPENAPI_ENDPOINTS_DECREASED("incompatible.openapi.endpoints.decreased", true),
+  OPERATION_ID_CHANGED("incompatible.operation.id.changed", false),
   REQUEST_BODY_REQUIRED_INCREASED("incompatible.request.body.increased", true),
   REQUEST_CONTENT_DECREASED("incompatible.request.content.decreased", true),
   REQUEST_ENUM_DECREASED("incompatible.request.enum.decreased", true),

core/src/main/java/org/openapitools/openapidiff/core/model/ChangedOpenApi.java

@@ -143,8 +143,8 @@ public int hashCode() {
         changedExtensions);
   }
 
-  @java.lang.Override
-  public java.lang.String toString() {
+  @Override
+  public String toString() {
     return "ChangedOpenApi(oldSpecOpenApi="
         + this.getOldSpecOpenApi()
         + ", newSpecOpenApi="

core/src/main/java/org/openapitools/openapidiff/core/model/ChangedOperation.java

@@ -7,6 +7,7 @@
 import java.util.Arrays;
 import java.util.List;
 import java.util.Objects;
+import org.openapitools.openapidiff.core.model.schema.ChangedOperationId;
 
 public class ChangedOperation implements ComposedChanged {
   private Operation oldOperation;
@@ -15,7 +16,7 @@ public class ChangedOperation implements ComposedChanged {
   private PathItem.HttpMethod httpMethod;
   private ChangedMetadata summary;
   private ChangedMetadata description;
-  private ChangedMetadata operationId;
+  private ChangedOperationId operationId;
   private boolean deprecated;
   private ChangedParameters parameters;
   private ChangedRequestBody requestBody;
@@ -92,7 +93,7 @@ public ChangedMetadata getDescription() {
     return this.description;
   }
 
-  public ChangedMetadata getOperationId() {
+  public ChangedOperationId getOperationId() {
     return this.operationId;
   }
 
@@ -150,7 +151,7 @@ public ChangedOperation setDescription(final ChangedMetadata description) {
     return this;
   }
 
-  public ChangedOperation setOperationId(final ChangedMetadata operationId) {
+  public ChangedOperation setOperationId(final ChangedOperationId operationId) {
     this.operationId = operationId;
     return this;
   }

core/src/main/java/org/openapitools/openapidiff/core/model/schema/ChangedOperationId.java

@@ -0,0 +1,40 @@
+package org.openapitools.openapidiff.core.model.schema;
+
+import static org.openapitools.openapidiff.core.model.BackwardIncompatibleProp.OPERATION_ID_CHANGED;
+
+import java.util.Objects;
+import org.openapitools.openapidiff.core.model.Changed;
+import org.openapitools.openapidiff.core.model.DiffContext;
+import org.openapitools.openapidiff.core.model.DiffResult;
+
+public class ChangedOperationId implements Changed {
+
+  private final String left;
+  private final String right;
+  private final DiffContext context;
+
+  public ChangedOperationId(String left, String right, DiffContext context) {
+    this.left = left;
+    this.right = right;
+    this.context = context;
+  }
+
+  @Override
+  public DiffResult isChanged() {
+    if (Objects.equals(left, right)) {
+      return DiffResult.NO_CHANGES;
+    }
+    if (OPERATION_ID_CHANGED.enabled(context)) {
+      return DiffResult.INCOMPATIBLE;
+    }
+    return DiffResult.METADATA;
+  }
+
+  public String getLeft() {
+    return this.left;
+  }
+
+  public String getRight() {
+    return this.right;
+  }
+}

core/src/test/java/org/openapitools/openapidiff/core/backcompat/OperationBCTest.java

@@ -1,9 +1,11 @@
 package org.openapitools.openapidiff.core.backcompat;
 
 import static org.openapitools.openapidiff.core.TestUtils.assertSpecChangedButCompatible;
+import static org.openapitools.openapidiff.core.TestUtils.assertSpecIncompatible;
 import static org.openapitools.openapidiff.core.TestUtils.assertSpecUnchanged;
 
 import org.junit.jupiter.api.Test;
+import org.openapitools.openapidiff.core.model.BackwardIncompatibleProp;
 
 public class OperationBCTest {
   private final String BASE = "bc_operation_base.yaml";
@@ -17,4 +19,14 @@ public void unchanged() {
   public void changedButCompatible() {
     assertSpecChangedButCompatible(BASE, "bc_operation_changed_but_compatible.yaml");
   }
+
+  @Test
+  public void operationIdChangedButCompatible() {
+    assertSpecChangedButCompatible(BASE, "bc_operation_changed_incompatible_operation_id.yaml");
+  }
+
+  @Test
+  public void operationIdChangedInCompatibleWithFlagSet() {
+    assertSpecIncompatible(BASE, "bc_operation_changed_incompatible_operation_id.yaml", BackwardIncompatibleProp.OPERATION_ID_CHANGED);
+  }
 }

core/src/test/resources/bc_operation_changed_incompatible_operation_id.yaml

@@ -0,0 +1,16 @@
+openapi: 3.0.0
+info:
+  description: myDesc
+  title: myTitle
+  version: 1.0.0
+paths:
+  /widgets:
+    get:
+      operationId: listWidgetsV2
+      responses:
+        '200':
+          description: successful operation
+          content:
+            application/json:
+              schema:
+                type: string