[dart-dio] Fix nullable inline object models

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

@@ -2891,7 +2891,7 @@ protected void updateModelForComposedSchema(CodegenModel m, Schema schema, Map<S
             addAdditionPropertiesToCodeGenModel(m, schema);
         }
 
-        if (Boolean.TRUE.equals(schema.getNullable())) {
+        if (ModelUtils.isNullable(schema)) {
             m.isNullable = Boolean.TRUE;
         }
 
@@ -3132,7 +3132,7 @@ public CodegenModel fromModel(String name, Schema schema) {
         if (!ModelUtils.isArraySchema(schema)) {
             m.dataType = getSchemaType(schema);
         }
-        if (!ModelUtils.isAnyType(schema) && Boolean.TRUE.equals(schema.getNullable())) {
+        if (!ModelUtils.isAnyType(schema) && ModelUtils.isNullable(schema)) {
             m.isNullable = Boolean.TRUE;
         }
 
@@ -4108,9 +4108,7 @@ public CodegenProperty fromProperty(String name, Schema p, boolean required, boo
         if (p.getWriteOnly() != null) {
             property.isWriteOnly = p.getWriteOnly();
         }
-        if (p.getNullable() != null) {
-            property.isNullable = p.getNullable();
-        }
+        property.isNullable = ModelUtils.isNullable(p);
 
         if (p.getExtensions() != null && !p.getExtensions().isEmpty()) {
             property.getVendorExtensions().putAll(p.getExtensions());
@@ -4160,11 +4158,8 @@ public CodegenProperty fromProperty(String name, Schema p, boolean required, boo
         }
 
         // set isNullable using nullable or x-nullable in the schema
-        if (referencedSchema.getNullable() != null) {
-            property.isNullable = referencedSchema.getNullable();
-        } else if (referencedSchema.getExtensions() != null &&
-                referencedSchema.getExtensions().containsKey(X_NULLABLE)) {
-            property.isNullable = (Boolean) referencedSchema.getExtensions().get(X_NULLABLE);
+        if (referencedSchema != p) {
+            property.isNullable = property.isNullable || ModelUtils.isNullable(referencedSchema);
         }
 
         final XML referencedSchemaXml = referencedSchema.getXml();
@@ -4263,10 +4258,8 @@ public CodegenProperty fromProperty(String name, Schema p, boolean required, boo
         if (original != null) {
             p = original;
             // evaluate common attributes if defined in the top level
-            if (p.getNullable() != null) {
-                property.isNullable = p.getNullable();
-            } else if (p.getExtensions() != null && p.getExtensions().containsKey(X_NULLABLE)) {
-                property.isNullable = (Boolean) p.getExtensions().get(X_NULLABLE);
+            if (hasNullableMarker(p)) {
+                property.isNullable = ModelUtils.isNullable(p);
             }
 
             if (p.getReadOnly() != null) {
@@ -4329,6 +4322,13 @@ public CodegenProperty fromProperty(String name, Schema p, boolean required, boo
      * @param cp codegen property
      * @param p  schema
      */
+    private static boolean hasNullableMarker(Schema schema) {
+        return schema != null && (schema.getNullable() != null ||
+                schema.getTypes() != null && schema.getTypes().contains("null") ||
+                schema.getExtensions() != null && schema.getExtensions().containsKey(X_NULLABLE) ||
+                ModelUtils.isNullableComposedSchema(schema));
+    }
+
     void updateDefaultToEmptyContainer(CodegenProperty cp, Schema p) {
         if (cp.isArray) {
             if (!cp.required) { // optional
@@ -5463,9 +5463,7 @@ public CodegenParameter fromParameter(Parameter parameter, Set<String> imports)
         codegenParameter.setTypeProperties(parameterSchema, openAPI);
         codegenParameter.setComposedSchemas(getComposedSchemas(parameterSchema));
 
-        if (Boolean.TRUE.equals(parameterSchema.getNullable())) { // use nullable defined in the spec
-            codegenParameter.isNullable = true;
-        }
+        codegenParameter.isNullable = ModelUtils.isNullable(parameterSchema);
 
         if (parameter.getStyle() != null) {
             codegenParameter.style = parameter.getStyle().toString();
@@ -8221,10 +8219,8 @@ public CodegenParameter fromRequestBody(RequestBody body, Set<String> imports, S
         // restore original schema with description, extensions etc
         if (original != null) {
             // evaluate common attributes such as description if defined in the top level
-            if (original.getNullable() != null) {
-                codegenParameter.isNullable = original.getNullable();
-            } else if (original.getExtensions() != null && original.getExtensions().containsKey(X_NULLABLE)) {
-                codegenParameter.isNullable = (Boolean) original.getExtensions().get(X_NULLABLE);
+            if (hasNullableMarker(original)) {
+                codegenParameter.isNullable = ModelUtils.isNullable(original);
             }
 
             if (original.getExtensions() != null) {

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

@@ -826,13 +826,10 @@ private void flattenProperties(OpenAPI openAPI, Map<String, Schema> properties,
                 Schema model = modelFromProperty(openAPI, op, modelName);
                 String existing = matchGenerated(model);
                 if (existing != null) {
-                    Schema schema = new Schema().$ref(existing);
-                    schema.setRequired(op.getRequired());
-                    propsToUpdate.put(key, schema);
+                    propsToUpdate.put(key, makeSchema(existing, op));
                 } else {
                     modelName = addSchemas(modelName, model);
-                    Schema schema = new Schema().$ref(modelName);
-                    schema.setRequired(op.getRequired());
+                    Schema schema = makeSchema(modelName, op);
                     propsToUpdate.put(key, schema);
                     modelsToAdd.put(modelName, model);
                 }
@@ -846,23 +843,17 @@ private void flattenProperties(OpenAPI openAPI, Map<String, Schema> properties,
                         Schema innerModel = modelFromProperty(openAPI, op, modelName);
                         String existing = matchGenerated(innerModel);
                         if (existing != null) {
-                            Schema schema = new Schema().$ref(existing);
-                            schema.setRequired(op.getRequired());
-                            property.setItems(schema);
+                            property.setItems(makeSchema(existing, op));
                         } else {
                             modelName = addSchemas(modelName, innerModel);
-                            Schema schema = new Schema().$ref(modelName);
-                            schema.setRequired(op.getRequired());
-                            property.setItems(schema);
+                            property.setItems(makeSchema(modelName, op));
                         }
                     }
                 } else if (ModelUtils.isComposedSchema(inner)) {
                     String innerModelName = resolveModelName(inner.getTitle(), path + "_" + key);
                     gatherInlineModels(inner, innerModelName);
                     innerModelName = addSchemas(innerModelName, inner);
-                    Schema schema = new Schema().$ref(innerModelName);
-                    schema.setRequired(inner.getRequired());
-                    property.setItems(schema);
+                    property.setItems(makeSchema(innerModelName, inner));
                 } else {
                     LOGGER.debug("Schema not yet handled in model resolver: {}", inner);
                 }
@@ -876,23 +867,17 @@ private void flattenProperties(OpenAPI openAPI, Map<String, Schema> properties,
                         Schema innerModel = modelFromProperty(openAPI, op, modelName);
                         String existing = matchGenerated(innerModel);
                         if (existing != null) {
-                            Schema schema = new Schema().$ref(existing);
-                            schema.setRequired(op.getRequired());
-                            property.setAdditionalProperties(schema);
+                            property.setAdditionalProperties(makeSchema(existing, op));
                         } else {
                             modelName = addSchemas(modelName, innerModel);
-                            Schema schema = new Schema().$ref(modelName);
-                            schema.setRequired(op.getRequired());
-                            property.setAdditionalProperties(schema);
+                            property.setAdditionalProperties(makeSchema(modelName, op));
                         }
                     }
                 } else if (ModelUtils.isComposedSchema(inner)) {
                     String innerModelName = resolveModelName(inner.getTitle(), path + "_" + key);
                     gatherInlineModels(inner, innerModelName);
                     innerModelName = addSchemas(innerModelName, inner);
-                    Schema schema = new Schema().$ref(innerModelName);
-                    schema.setRequired(inner.getRequired());
-                    property.setAdditionalProperties(schema);
+                    property.setAdditionalProperties(makeSchema(innerModelName, inner));
                 } else {
                     LOGGER.debug("Schema not yet handled in model resolver: {}", inner);
                 }
@@ -907,9 +892,7 @@ private void flattenProperties(OpenAPI openAPI, Map<String, Schema> properties,
                     String propertyModelName = resolveModelName(property.getTitle(), path + "_" + key);
                     gatherInlineModels(property, propertyModelName);
                     propertyModelName = addSchemas(propertyModelName, property);
-                    Schema schema = new Schema().$ref(propertyModelName);
-                    schema.setRequired(property.getRequired());
-                    propsToUpdate.put(key, schema);
+                    propsToUpdate.put(key, makeSchema(propertyModelName, property));
                 }
             } else {
                 LOGGER.debug("Schema not yet handled in model resolver: {}", property);
@@ -1007,6 +990,9 @@ private Schema makeSchemaInComponents(String name, Schema schema) {
             refSchema = new Schema().$ref(name);
         }
         this.copyVendorExtensions(schema, refSchema);
+        if (ModelUtils.isNullable(schema)) {
+            refSchema.setNullable(true);
+        }
 
         return refSchema;
     }
@@ -1020,6 +1006,10 @@ private Schema makeSchemaInComponents(String name, Schema schema) {
      */
     private Schema makeSchema(String ref, Schema property) {
         Schema newProperty = new Schema().$ref(ref);
+        newProperty.setRequired(property.getRequired());
+        if (ModelUtils.isNullable(property)) {
+            newProperty.setNullable(true);
+        }
         this.copyVendorExtensions(property, newProperty);
         return newProperty;
     }

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

@@ -1767,9 +1767,10 @@ public static boolean isExtensionParent(Schema schema) {
      * Return true if the 'nullable' attribute is set to true in the schema, i.e. if the value
      * of the property can be the null value.
      * <p>
-     * In addition, if the OAS document is 3.1 or above, isNullable returns true if the input
-     * schema is a 'oneOf' composed document with at most two children, and one of the children
-     * is the 'null' type.
+     * In addition, isNullable returns true if the input schema uses JSON Schema nullability
+     * forms adopted by OAS 3.1: a 'oneOf' composed document with at most two children where
+     * one child is the 'null' type, or a type-array form where one of the types is 'null'.
+     * This method checks schema shape only and does not validate the OpenAPI document version.
      * <p>
      * The caller is responsible for resolving schema references before invoking isNullable.
      * If the input schema is a $ref and the referenced schema has 'nullable: true', this method
@@ -1794,6 +1795,9 @@ public static boolean isNullable(Schema schema) {
         if (schema.getExtensions() != null && schema.getExtensions().get(X_NULLABLE) != null) {
             return Boolean.parseBoolean(schema.getExtensions().get(X_NULLABLE).toString());
         }
+        if (schema.getTypes() != null && schema.getTypes().contains("null")) {
+            return true;
+        }
         // In OAS 3.1, the recommended way to define a nullable property or object is to use oneOf.
         if (isComposedSchema(schema)) {
             return isNullableComposedSchema(schema);

modules/openapi-generator/src/main/java/org/openapitools/codegen/validations/oas/OpenApiSchemaValidations.java

@@ -1,6 +1,7 @@
 package org.openapitools.codegen.validations.oas;
 
 import io.swagger.v3.oas.models.media.Schema;
+import org.openapitools.codegen.CodegenConstants;
 import org.openapitools.codegen.utils.ModelUtils;
 import org.openapitools.codegen.utils.SemVer;
 import org.openapitools.codegen.validation.GenericValidator;
@@ -120,7 +121,7 @@ private static ValidationRule.Result checkNullableAttribute(SchemaWrapper schema
         if (schemaWrapper.getOpenAPI() != null) {
             SemVer version = new SemVer(schemaWrapper.getOpenAPI().getOpenapi());
             if (version.atLeast("3.1")) {
-                if (ModelUtils.isNullable(schema)) {
+                if (usesNullableAttribute(schema)) {
                     result = new ValidationRule.Fail();
                     result.setDetails(String.format(Locale.ROOT,
                             "OAS document is version '%s'. Schema '%s' uses 'nullable' attribute, which has been deprecated in OAS 3.1.",
@@ -132,6 +133,18 @@ private static ValidationRule.Result checkNullableAttribute(SchemaWrapper schema
         return result;
     }
 
+    private static boolean usesNullableAttribute(Schema schema) {
+        if (schema == null) {
+            return false;
+        }
+        if (Boolean.TRUE.equals(schema.getNullable())) {
+            return true;
+        }
+        return schema.getExtensions() != null
+                && schema.getExtensions().get(CodegenConstants.X_NULLABLE) != null
+                && Boolean.parseBoolean(schema.getExtensions().get(CodegenConstants.X_NULLABLE).toString());
+    }
+
     private static String nameOf(Schema schema) {
         return schema.getName() != null ? schema.getName() : schema.getTitle();
     }

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

@@ -2462,6 +2462,25 @@ public void schemaMappingWithNullableAllOfProperty() {
                 "dataType must resolve to the referenced schema name");
     }
 
+    @Test
+    public void nullableTypeArrayProperty() {
+        DefaultCodegen codegen = new DefaultCodegen();
+        OpenAPI openAPI = TestUtils.parseFlattenSpec("src/test/resources/3_1/dart-dio/issue_23866.yaml");
+        codegen.setOpenAPI(openAPI);
+
+        CodegenModel model = codegen.fromModel(
+                "EnvelopeNullableLoginResponse",
+                openAPI.getComponents().getSchemas().get("EnvelopeNullableLoginResponse"));
+
+        CodegenProperty data = model.vars.stream()
+                .filter(v -> "data".equals(v.name))
+                .findFirst()
+                .orElseThrow(() -> new AssertionError("data property not found"));
+
+        assertTrue(data.isNullable,
+                "data must be nullable because its OAS 3.1 type array includes null");
+    }
+
     @Test
     public void operationIdNameMapping() {
         DefaultCodegen codegen = new DefaultCodegen();

modules/openapi-generator/src/test/java/org/openapitools/codegen/dart/dio/DartDioModelTest.java

@@ -520,4 +520,26 @@ public void nestedArrayItemsCanBeNullable() {
 
         Assert.assertEquals(codegen.getTypeDeclaration(schema), "BuiltList<BuiltList<String?>>");
     }
+
+    @Test(description = "OAS 3.1 nullable inline object properties keep nullable field type")
+    public void nullableInlineObjectPropertyWithTypeArray() {
+        final OpenAPI openAPI = TestUtils.parseFlattenSpec("src/test/resources/3_1/dart-dio/issue_23866.yaml");
+        final DartDioClientCodegen codegen = new DartDioClientCodegen();
+        codegen.additionalProperties().put(CodegenConstants.SERIALIZATION_LIBRARY, DartDioClientCodegen.SERIALIZATION_LIBRARY_BUILT_VALUE);
+        codegen.processOpts();
+        codegen.setOpenAPI(openAPI);
+
+        final Schema model = openAPI.getComponents().getSchemas().get("EnvelopeNullableLoginResponse");
+        final CodegenModel cm = codegen.fromModel("EnvelopeNullableLoginResponse", model);
+
+        final CodegenProperty data = cm.vars.stream()
+                .filter(property -> "data".equals(property.baseName))
+                .findFirst()
+                .orElseThrow(() -> new AssertionError("data property not found"));
+
+        Assert.assertEquals(data.dataType, "EnvelopeNullableLoginResponseData");
+        Assert.assertEquals(data.datatypeWithEnum, "EnvelopeNullableLoginResponseData");
+        Assert.assertTrue(data.required);
+        Assert.assertTrue(data.isNullable);
+    }
 }

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

@@ -30,6 +30,7 @@
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.HashMap;
+import java.util.LinkedHashSet;
 import java.util.List;
 import java.util.Map;
 
@@ -615,6 +616,14 @@ public void simplifyOneOfAnyOfWithOnlyOneNonNullSubSchemaKeepsParentDescription(
         assertEquals(anyOfSchemaWithChildDescription.getDescription(), "Child description");
     }
 
+    @Test
+    public void isNullableWithTypeArrayNull() {
+        Schema<?> schema = new Schema<>();
+        schema.setTypes(new LinkedHashSet<>(Arrays.asList("object", "null")));
+
+        assertTrue(ModelUtils.isNullable(schema));
+    }
+
     @Test
     public void isNullTypeSchemaTest() {
         OpenAPI openAPI = TestUtils.parseSpec("src/test/resources/3_0/null_schema_test.yaml");

modules/openapi-generator/src/test/java/org/openapitools/codegen/validations/oas/OpenApiSchemaValidationsTest.java

@@ -1,5 +1,6 @@
 package org.openapitools.codegen.validations.oas;
 
+import io.swagger.v3.oas.models.OpenAPI;
 import io.swagger.v3.oas.models.media.*;
 import org.openapitools.codegen.validation.Invalid;
 import org.openapitools.codegen.validation.ValidationResult;
@@ -8,6 +9,7 @@
 import org.testng.annotations.Test;
 
 import java.util.Arrays;
+import java.util.LinkedHashSet;
 import java.util.List;
 import java.util.stream.Collectors;
 
@@ -67,6 +69,26 @@ public void testOneOfWithSiblingPropertiesDisabledRule(Schema schema, boolean ma
         Assert.assertEquals(warnings.size(), 0, "Expected rule to be disabled.");
     }
 
+    @Test(description = "OAS 3.1 type-array null is not the deprecated nullable attribute")
+    public void testNullableAttributeRecommendationIgnoresTypeArrayNull() {
+        RuleConfiguration config = new RuleConfiguration();
+        config.setEnableRecommendations(true);
+        OpenApiSchemaValidations validator = new OpenApiSchemaValidations(config);
+
+        OpenAPI openAPI = new OpenAPI().openapi("3.1.0");
+        Schema schema = new Schema();
+        schema.setTypes(new LinkedHashSet<>(Arrays.asList("object", "null")));
+
+        ValidationResult result = validator.validate(new SchemaWrapper(openAPI, schema));
+        Assert.assertNotNull(result.getWarnings());
+
+        List<Invalid> warnings = result.getWarnings().stream()
+                .filter(invalid -> "Schema uses the 'nullable' attribute.".equals(invalid.getRule().getDescription()))
+                .collect(Collectors.toList());
+
+        Assert.assertEquals(warnings.size(), 0, "Expected type-array null not to trigger nullable attribute recommendation.");
+    }
+
     @DataProvider(name = "apacheNginxRecommendationExpectations")
     public Object[][] apacheNginxRecommendationExpectations() {
         return new Object[][]{
@@ -128,4 +150,4 @@ private ComposedSchema getAnyOfSample(boolean withProperties) {
 
         return schema;
     }
-}
+}