Fix: False positive breaking change when removing optional field from response (#327)

Author: orange-buffalo

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

@@ -137,8 +137,13 @@ private DiffResult calculateCoreChanged() {
         && !discriminatorPropertyChanged) {
       return DiffResult.NO_CHANGES;
     }
+    boolean missingRequiredProperties =
+        oldSchema != null
+            && oldSchema.getRequired() != null
+            && missingProperties.keySet().stream()
+                .anyMatch(missingProperty -> oldSchema.getRequired().contains(missingProperty));
     boolean compatibleForResponse =
-        missingProperties.isEmpty() && (oldSchema == null || newSchema != null);
+        !missingRequiredProperties && (oldSchema == null || newSchema != null);
     if ((context.isRequest() && compatibleForRequest()
             || context.isResponse() && compatibleForResponse)
         && !changedType

core/src/test/java/org/openapitools/openapidiff/core/AddPropDiffTest.java

@@ -1,7 +1,7 @@
 package org.openapitools.openapidiff.core;
 
 import static org.openapitools.openapidiff.core.TestUtils.assertOpenApiAreEquals;
-import static org.openapitools.openapidiff.core.TestUtils.assertOpenApiBackwardIncompatible;
+import static org.openapitools.openapidiff.core.TestUtils.assertOpenApiBackwardCompatible;
 
 import org.junit.jupiter.api.Test;
 
@@ -16,6 +16,6 @@ public void testDiffSame() {
 
   @Test
   public void testDiffDifferent() {
-    assertOpenApiBackwardIncompatible(OPENAPI_DOC1, OPENAPI_DOC2);
+    assertOpenApiBackwardCompatible(OPENAPI_DOC1, OPENAPI_DOC2, true);
   }
 }

core/src/test/resources/recursive_model_1.yaml

@@ -19,6 +19,7 @@ components:
   schemas:
     B:
       type: object
+      required: ["message2"]
       properties:
         message:
           type: string
@@ -27,4 +28,4 @@ components:
         details:
           type: array
           items:
-            $ref: '#/components/schemas/B'
+            $ref: '#/components/schemas/B'