implement feedback from CR

Author: Picazsoo

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

@@ -7142,6 +7142,10 @@ public void setIgnoreFilePathOverride(final String ignoreFileOverride) {
 
     public List<String> getPropertyAsStringList(String propertyKey) {
         final Object value = additionalProperties.get(propertyKey);
+        return getObjectAsStringList(value);
+    }
+
+    public static List<String> getObjectAsStringList(Object value) {
         if (value instanceof List) {
             List<?> list = (List<?>) value;
             List<String> stringList = new ArrayList<>();
@@ -7159,10 +7163,14 @@ public List<String> getPropertyAsStringList(String propertyKey) {
 
     public Map<String, String> getPropertyAsStringMap(String propertyKey) {
         final Object value = additionalProperties.get(propertyKey);
+        return getObjectAsStringMap(value);
+    }
+
+    public static Map<String, String> getObjectAsStringMap(Object value) {
         if (value instanceof Map) {
             Map<?, ?> rawMap = (Map<?, ?>) value;
             Map<String, String> stringMap = new HashMap<>();
-            for (Map.Entry<?, ?> entry : rawMap.entrySet()) {
+            for (Entry<?, ?> entry : rawMap.entrySet()) {
                 stringMap.put(String.valueOf(entry.getKey()), String.valueOf(entry.getValue()));
             }
             return stringMap;
@@ -7172,10 +7180,14 @@ public Map<String, String> getPropertyAsStringMap(String propertyKey) {
 
     public Map<String, List<String>> getPropertyAsStringListMap(String propertyKey) {
         final Object value = additionalProperties.get(propertyKey);
+        return getObjectAsStringListMap(value);
+    }
+
+    public static Map<String, List<String>> getObjectAsStringListMap(Object value) {
         if (value instanceof Map) {
             Map<?, ?> rawMap = (Map<?, ?>) value;
             Map<String, List<String>> stringMap = new HashMap<>();
-            for (Map.Entry<?, ?> entry : rawMap.entrySet()) {
+            for (Entry<?, ?> entry : rawMap.entrySet()) {
                 Object entryValue = entry.getValue();
                 if (entryValue instanceof List) {
                     List<String> stringList = ((List<?>) entryValue).stream()

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

@@ -2012,13 +2012,23 @@ public ModelsMap postProcessModels(ModelsMap objs) {
                 listIterator.add(newImportMap);
             }
         }
+        // make sure the x-implements is always a List and always at least empty
+        for (ModelMap mo : objs.getModels()) {
+            CodegenModel cm = mo.getModel();
+            if (cm.getVendorExtensions().containsKey(X_IMPLEMENTS)) {
+                List<String> xImplements = getObjectAsStringList(cm.getVendorExtensions().get(X_IMPLEMENTS));
+                cm.getVendorExtensions().replace(X_IMPLEMENTS, xImplements);
+            } else {
+                cm.getVendorExtensions().put(X_IMPLEMENTS, new ArrayList<String>());
+            }
+        }
 
         // skip interfaces predefined in open api spec in x-implements via additional property xImplementsSkip
         if (!this.xImplementsSkip.isEmpty()) {
             for (ModelMap mo : objs.getModels()) {
                 CodegenModel cm = mo.getModel();
-                if (cm.getVendorExtensions().containsKey(X_IMPLEMENTS)) {
-                    List<String> xImplementsInModelOriginal = (List<String>) cm.getVendorExtensions().get(X_IMPLEMENTS);
+                if (!getObjectAsStringList(cm.getVendorExtensions().get(X_IMPLEMENTS)).isEmpty()) {
+                    List<String> xImplementsInModelOriginal = getObjectAsStringList(cm.getVendorExtensions().get(X_IMPLEMENTS));
                     List<String> xImplementsInModelSkipped = xImplementsInModelOriginal
                             .stream()
                             .filter(o -> this.xImplementsSkip.contains(o))
@@ -2040,8 +2050,7 @@ public ModelsMap postProcessModels(ModelsMap objs) {
                 CodegenModel cm = mo.getModel();
                 if (this.schemaImplements.containsKey(cm.getSchemaName())) {
                     LOGGER.info("Adding interface(s) {} configured via config option '{}' to model {}", this.schemaImplements.get(cm.getSchemaName()), SCHEMA_IMPLEMENTS, cm.classname);
-                    cm.getVendorExtensions().putIfAbsent(X_IMPLEMENTS, new ArrayList<String>());
-                    List<String> xImplementsInModel = (List<String>) cm.getVendorExtensions().get(X_IMPLEMENTS);
+                    List<String> xImplementsInModel = getObjectAsStringList(cm.getVendorExtensions().get(X_IMPLEMENTS));
                     List<String> schemaImplements = this.schemaImplements.get(cm.getSchemaName());
                     List<String> combinedSchemaImplements = Stream.concat(xImplementsInModel.stream(), schemaImplements.stream())
                             .collect(Collectors.toList());
@@ -2051,12 +2060,15 @@ public ModelsMap postProcessModels(ModelsMap objs) {
             }
         }
 
-        // add x-implements for serializable to all models
-        for (ModelMap mo : objs.getModels()) {
-            CodegenModel cm = mo.getModel();
-            if (this.serializableModel) {
-                cm.getVendorExtensions().putIfAbsent(X_IMPLEMENTS, new ArrayList<String>());
-                ((ArrayList<String>) cm.getVendorExtensions().get(X_IMPLEMENTS)).add("Serializable");
+        // add Serializable to x-implements to all models if configured
+        if (this.serializableModel) {
+            for (ModelMap mo : objs.getModels()) {
+                CodegenModel cm = mo.getModel();
+                List<String> xImplements = new ArrayList<>(getObjectAsStringList(cm.getVendorExtensions().get(X_IMPLEMENTS)));
+                if (!xImplements.contains("Serializable")) {
+                    xImplements.add("Serializable");
+                }
+                cm.getVendorExtensions().replace(X_IMPLEMENTS, xImplements);
             }
         }