fix ModelUtils.getParentName returning name of first element in composed schema instead of null when there are multiple elements and it is not clear which one should be parent

Author: fkellner

modules/openapi-generator/src/main/java/org/openapitools/codegen/utils/ModelUtils.java

@@ -1573,17 +1573,18 @@ public static String getParentName(Schema composedSchema, Map<String, Schema> al
         List<String> refedWithoutDiscriminator = new ArrayList<>();
 
         if (interfaces != null && !interfaces.isEmpty()) {
+            List<String> parentNameCandidates = new ArrayList<>(interfaces.size());
             for (Schema schema : interfaces) {
                 // get the actual schema
                 if (StringUtils.isNotEmpty(schema.get$ref())) {
                     String parentName = getSimpleRef(schema.get$ref());
                     Schema s = allSchemas.get(parentName);
                     if (s == null) {
                         LOGGER.error("Failed to obtain schema from {}", parentName);
-                        return "UNKNOWN_PARENT_NAME";
+                        parentNameCandidates.add("UNKNOWN_PARENT_NAME");
                     } else if (hasOrInheritsDiscriminator(s, allSchemas, new ArrayList<Schema>())) {
                         // discriminator.propertyName is used or x-parent is used
-                        return parentName;
+                        parentNameCandidates.add(parentName);
                     } else {
                         // not a parent since discriminator.propertyName or x-parent is not set
                         hasAmbiguousParents = true;
@@ -1600,6 +1601,12 @@ public static String getParentName(Schema composedSchema, Map<String, Schema> al
                     }
                 }
             }
+            if (parentNameCandidates.size() > 1) {
+                // unclear which one should be the parent
+                return null;
+            } else if (parentNameCandidates.size() == 1) {
+                return parentNameCandidates.get(0);
+            }
             if (refedWithoutDiscriminator.size() == 1 && nullSchemaChildrenCount == 1) {
                 // One schema is a $ref and the other is the 'null' type, so the parent is obvious.
                 // In this particular case there is no need to specify a discriminator.

modules/openapi-generator/src/test/java/org/openapitools/codegen/utils/ModelUtilsTest.java

@@ -675,4 +675,12 @@ public void testModelWithPropertiesOnly() {
         testSchema.setAdditionalProperties(new Schema().type("string"));
         assertFalse(ModelUtils.isModelWithPropertiesOnly(testSchema));
     }
+
+    @Test
+    public void getParentNameMultipleInterfacesTest() {
+        OpenAPI openAPI = TestUtils.parseFlattenSpec("src/test/resources/3_0/oneOf_inheritance.yaml");
+        Map<String, Schema> allSchemas = openAPI.getComponents().getSchemas();
+        Schema composedSchema = allSchemas.get("RandomAnimalsResponse_animals_inner");
+        assertNull(ModelUtils.getParentName(composedSchema, allSchemas));
+    }
 }