[core] Keep the defaultToEmptyContainer default off schemas shared between properties

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

@@ -4383,14 +4383,23 @@ public CodegenProperty fromProperty(String name, Schema p, boolean required, boo
         }
 
         // override defaultValue if it's not set and defaultToEmptyContainer is set
-        if (p.getDefault() == null && defaultToEmptyContainer) {
+        boolean emptyContainerDefault = p.getDefault() == null && defaultToEmptyContainer;
+        boolean defaultSetFlag = p.getDefaultSetFlag();
+        if (emptyContainerDefault) {
             updateDefaultToEmptyContainer(property, p);
         }
 
         // set the default value
         property.defaultValue = toDefaultValue(property, p);
         property.defaultValueWithParam = toDefaultValueWithParam(name, p);
 
+        if (emptyContainerDefault) {
+            // p may be shared with other properties (e.g. via $ref or allOf) and the empty-container
+            // default depends on this property's required flag, so take it off the schema again
+            p.setDefault(null);
+            p.setDefaultSetFlag(defaultSetFlag);
+        }
+
         LOGGER.debug("debugging from property return: {}", property);
         schemaCodegenPropertyCache.put(ns, property);
         return property;

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

@@ -5893,6 +5893,32 @@ public void testMicroprofileNullableRequiredContainers_issue24776() {
                 .doesNotContain(" = ;");
     }
 
+    @Test
+    public void testDefaultToEmptyContainerDoesNotLeakAcrossSharedSchemaRefs_issue25522() {
+        final Path output = newTempFolder();
+        final CodegenConfigurator configurator = new CodegenConfigurator()
+                .setGeneratorName(JAVA_GENERATOR)
+                .setLibrary(JavaClientCodegen.RESTTEMPLATE)
+                .setAdditionalProperties(Map.of(
+                        CodegenConstants.MODEL_PACKAGE, "org.openapitools.client.model",
+                        "defaultToEmptyContainer", "array|map"
+                ))
+                .setInputSpec("src/test/resources/3_0/java/issue_25522.yaml")
+                .setOutputDir(output.toString().replace("\\", "/"));
+
+        List<File> files = new DefaultGenerator().opts(configurator.toClientOptInput()).generate();
+
+        validateJavaSourceFiles(files);
+        // requiredStrings and requiredMap come first and share their schema with the optional ones
+        assertThat(output.resolve("src/main/java/org/openapitools/client/model/ExampleObject.java")).content()
+                .contains("private List<String> requiredStrings = new ArrayList<>();")
+                .contains("private List<String> optionalStrings;")
+                .contains("private Map<String, String> requiredMap = new HashMap<>();")
+                .contains("private Map<String, String> optionalMap;");
+        // the spec declares no default, so none may leak into the exported copy
+        assertThat(output.resolve("api/openapi.yaml")).content().doesNotContain("default:");
+    }
+
     private static JavaClientCodegen newRetrofit2Codegen(Map<String, Object> properties) {
         JavaClientCodegen codegen = new JavaClientCodegen();
         codegen.setLibrary(JavaClientCodegen.RETROFIT_2);

modules/openapi-generator/src/test/resources/3_0/java/issue_25522.yaml

@@ -0,0 +1,39 @@
+openapi: 3.0.0
+info:
+  version: 1.0.0
+  title: Example API
+paths:
+  /info:
+    get:
+      operationId: getInfo
+      responses:
+        '200':
+          description: Successful operation
+          content:
+            application/json:
+              schema:
+                $ref: '#/components/schemas/ExampleObject'
+components:
+  schemas:
+    StringArray:
+      type: array
+      items:
+        type: string
+    StringMap:
+      type: object
+      additionalProperties:
+        type: string
+    ExampleObject:
+      type: object
+      properties:
+        requiredStrings:
+          $ref: '#/components/schemas/StringArray'
+        optionalStrings:
+          $ref: '#/components/schemas/StringArray'
+        requiredMap:
+          $ref: '#/components/schemas/StringMap'
+        optionalMap:
+          $ref: '#/components/schemas/StringMap'
+      required:
+        - requiredStrings
+        - requiredMap