[python] Preserve nested union container values

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

@@ -726,9 +726,31 @@ public Map<String, ModelsMap> postProcessAllModels(Map<String, ModelsMap> objs)
         }
 
         Map<String, ModelsMap> processed = super.postProcessAllModels(objs);
+        Set<String> composedModels = new HashSet<>();
         for (ModelsMap modelsMap : processed.values()) {
             for (ModelMap modelMap : modelsMap.getModels()) {
                 CodegenModel model = modelMap.getModel();
+                if (model != null && (hasOneOf(model) || hasAnyOf(model))) {
+                    composedModels.add(model.classname);
+                }
+            }
+        }
+        for (ModelsMap modelsMap : processed.values()) {
+            for (ModelMap modelMap : modelsMap.getModels()) {
+                CodegenModel model = modelMap.getModel();
+                if (model != null && (hasOneOf(model) || hasAnyOf(model))) {
+                    List<CodegenProperty> alternatives = hasOneOf(model)
+                            ? model.getComposedSchemas().getOneOf()
+                            : model.getComposedSchemas().getAnyOf();
+                    for (CodegenProperty property : alternatives) {
+                        if (property.isContainer) {
+                            String expression = fromDictExpression(property, "data", 0, composedModels);
+                            if (!expression.equals("data")) {
+                                property.vendorExtensions.put("x-py-from-dict", expression);
+                            }
+                        }
+                    }
+                }
                 if (model != null && model.oneOf.isEmpty() && model.anyOf.isEmpty()) {
                     for (CodegenProperty property : model.vars) {
                         if (property.vendorExtensions.containsKey(
@@ -751,6 +773,35 @@ public Map<String, ModelsMap> postProcessAllModels(Map<String, ModelsMap> objs)
         return processed;
     }
 
+    private String fromDictExpression(CodegenProperty property, String value, int depth,
+                                       Set<String> composedModels) {
+        String item = "_item" + depth;
+        if (property.isContainer && property.items != null) {
+            String expression = fromDictExpression(property.items, item, depth + 1, composedModels);
+            if (expression.equals(item)) {
+                return value;
+            }
+            if (property.isArray) {
+                return "([" + expression
+                        + " for " + item + " in " + value + "] if isinstance(" + value
+                        + ", list) else " + value + ")";
+            }
+            if (property.isMap) {
+                String key = "_key" + depth;
+                return "({" + key + ": " + expression
+                        + " for " + key + ", " + item + " in " + value + ".items()} if isinstance("
+                        + value + ", dict) else " + value + ")";
+            }
+        }
+        // Pydantic cannot decode raw values into the generated union wrappers.
+        // Ordinary models must retain Pydantic's existing defaults/field presence.
+        if (composedModels.contains(property.dataType)) {
+            return "(" + property.dataType + ".from_dict(" + value + ") if "
+                    + value + " is not None else None)";
+        }
+        return value;
+    }
+
     private void configurePublicNameInputs(List<CodegenProperty> properties) {
         for (CodegenProperty property : properties) {
             String publicName = (String) property.vendorExtensions.getOrDefault(

modules/openapi-generator/src/main/resources/python/_composed_model_dict.mustache

@@ -0,0 +1,9 @@
+def _to_dict(value: Any) -> Any:
+    if isinstance(value, list):
+        return [_to_dict(item) for item in value]
+    if isinstance(value, dict):
+        return {key: _to_dict(item) for key, item in value.items()}
+    if hasattr(value, "to_dict") and callable(value.to_dict):
+        return value.to_dict()
+    return value
+

modules/openapi-generator/src/main/resources/python/model_anyof.mustache

@@ -12,12 +12,16 @@ import re  # noqa: F401
 from typing import Union, Any, List, Set, TYPE_CHECKING, Optional, Dict
 from typing_extensions import Literal, Self
 from pydantic import Field
-{{#compatibleWithPythonLegacy}}
 from pydantic_core import to_jsonable_python
+{{#compatibleWithPythonLegacy}}
 
 
 {{>_legacy_model_dict_helpers}}
 
+{{/compatibleWithPythonLegacy}}
+{{^compatibleWithPythonLegacy}}
+
+{{>_composed_model_dict}}
 {{/compatibleWithPythonLegacy}}
 
 {{#lambda.uppercase}}{{{classname}}}{{/lambda.uppercase}}_ANY_OF_SCHEMAS = [{{#anyOf}}"{{.}}"{{^-last}}, {{/-last}}{{/anyOf}}]
@@ -119,12 +123,16 @@ class {{classname}}({{#parent}}{{{.}}}{{/parent}}{{^parent}}BaseModel{{/parent}}
         {{#isContainer}}
         # deserialize data into {{{dataType}}}
         try:
+            data = json.loads(json_str)
+            {{#vendorExtensions.x-py-from-dict}}
+            data = {{{vendorExtensions.x-py-from-dict}}}
+            {{/vendorExtensions.x-py-from-dict}}
             # validation
-            instance.{{vendorExtensions.x-py-name}} = json.loads(json_str)
+            instance.{{vendorExtensions.x-py-name}} = data
             # assign value to actual_instance
             instance.actual_instance = instance.{{vendorExtensions.x-py-name}}
             return instance
-        except (ValidationError, ValueError) as e:
+        except (ValidationError, ValueError, TypeError, AttributeError) as e:
             error_messages.append(str(e))
         {{/isContainer}}
         {{^isContainer}}
@@ -172,7 +180,7 @@ class {{classname}}({{#parent}}{{{.}}}{{/parent}}{{^parent}}BaseModel{{/parent}}
 {{/compatibleWithPythonLegacy}}
 {{^compatibleWithPythonLegacy}}
         else:
-            return json.dumps(self.actual_instance)
+            return json.dumps(to_jsonable_python(self.to_dict()))
 {{/compatibleWithPythonLegacy}}
 
 {{#compatibleWithPythonLegacy}}
@@ -198,10 +206,7 @@ class {{classname}}({{#parent}}{{{.}}}{{/parent}}{{^parent}}BaseModel{{/parent}}
         if self.actual_instance is None:
             return None
 
-        if hasattr(self.actual_instance, "to_dict") and callable(self.actual_instance.to_dict):
-            return self.actual_instance.to_dict()
-        else:
-            return self.actual_instance
+        return _to_dict(self.actual_instance)
 {{/compatibleWithPythonLegacy}}
 
     def to_str(self) -> str:

modules/openapi-generator/src/main/resources/python/model_oneof.mustache

@@ -10,12 +10,16 @@ import pprint
 from pydantic import StrictStr, Field
 from typing import Union, List, Set, Optional, Dict
 from typing_extensions import Literal, Self
-{{#compatibleWithPythonLegacy}}
 from pydantic_core import to_jsonable_python
+{{#compatibleWithPythonLegacy}}
 
 
 {{>_legacy_model_dict_helpers}}
 
+{{/compatibleWithPythonLegacy}}
+{{^compatibleWithPythonLegacy}}
+
+{{>_composed_model_dict}}
 {{/compatibleWithPythonLegacy}}
 
 {{#lambda.uppercase}}{{{classname}}}{{/lambda.uppercase}}_ONE_OF_SCHEMAS = [{{#oneOf}}"{{.}}"{{^-last}}, {{/-last}}{{/oneOf}}]
@@ -143,12 +147,16 @@ class {{classname}}({{#parent}}{{{.}}}{{/parent}}{{^parent}}BaseModel{{/parent}}
         {{#isContainer}}
         # deserialize data into {{{dataType}}}
         try:
+            data = json.loads(json_str)
+            {{#vendorExtensions.x-py-from-dict}}
+            data = {{{vendorExtensions.x-py-from-dict}}}
+            {{/vendorExtensions.x-py-from-dict}}
             # validation
-            instance.{{vendorExtensions.x-py-name}} = json.loads(json_str)
+            instance.{{vendorExtensions.x-py-name}} = data
             # assign value to actual_instance
             instance.actual_instance = instance.{{vendorExtensions.x-py-name}}
             match += 1
-        except (ValidationError, ValueError) as e:
+        except (ValidationError, ValueError, TypeError, AttributeError) as e:
             error_messages.append(str(e))
         {{/isContainer}}
         {{^isContainer}}
@@ -199,7 +207,7 @@ class {{classname}}({{#parent}}{{{.}}}{{/parent}}{{^parent}}BaseModel{{/parent}}
 {{/compatibleWithPythonLegacy}}
 {{^compatibleWithPythonLegacy}}
         else:
-            return json.dumps(self.actual_instance)
+            return json.dumps(to_jsonable_python(self.to_dict()))
 {{/compatibleWithPythonLegacy}}
 
 {{#compatibleWithPythonLegacy}}
@@ -225,11 +233,7 @@ class {{classname}}({{#parent}}{{{.}}}{{/parent}}{{^parent}}BaseModel{{/parent}}
         if self.actual_instance is None:
             return None
 
-        if hasattr(self.actual_instance, "to_dict") and callable(self.actual_instance.to_dict):
-            return self.actual_instance.to_dict()
-        else:
-            # primitive type
-            return self.actual_instance
+        return _to_dict(self.actual_instance)
 {{/compatibleWithPythonLegacy}}
 
     def to_str(self) -> str:

modules/openapi-generator/src/test/resources/3_0/python/petstore-with-fake-endpoints-models-for-testing.yaml

@@ -2579,6 +2579,60 @@ components:
           $ref: '#/components/schemas/Pig'
         nested_oneof_enum_string:
           $ref: '#/components/schemas/OneOfEnumString'
+    OneOfContainer:
+      oneOf:
+        - type: string
+        - type: array
+          minItems: 1
+          items:
+            $ref: '#/components/schemas/Pig'
+        - type: object
+          additionalProperties:
+            $ref: '#/components/schemas/Pig'
+        - type: array
+          minItems: 1
+          items:
+            type: integer
+        - type: array
+          minItems: 1
+          items:
+            $ref: '#/components/schemas/EnumString1'
+        - type: array
+          minItems: 1
+          items:
+            $ref: '#/components/schemas/NullableClass'
+    AnyOfContainer:
+      anyOf:
+        - type: string
+        - type: array
+          minItems: 1
+          items:
+            $ref: '#/components/schemas/AnyOfPig'
+        - type: object
+          additionalProperties:
+            $ref: '#/components/schemas/AnyOfPig'
+        - type: array
+          minItems: 1
+          items:
+            type: integer
+        - type: array
+          minItems: 1
+          items:
+            $ref: '#/components/schemas/EnumString1'
+        - type: array
+          minItems: 1
+          items:
+            $ref: '#/components/schemas/NullableClass'
+    NestedUnionContainer:
+      oneOf:
+        - type: string
+        - type: array
+          items:
+            type: object
+            additionalProperties:
+              type: array
+              items:
+                $ref: '#/components/schemas/Pig'
     Self-Reference-Model:
       type: object
       properties:

samples/client/others/python-legacy-model-dictionaries/legacy_model_dict_client/models/any_of_model.py

@@ -182,21 +182,23 @@ def from_json(cls, json_str: str) -> Self:
              error_messages.append(str(e))
         # deserialize data into List[NestedModel]
         try:
+            data = json.loads(json_str)
             # validation
-            instance.anyof_schema_2_validator = json.loads(json_str)
+            instance.anyof_schema_2_validator = data
             # assign value to actual_instance
             instance.actual_instance = instance.anyof_schema_2_validator
             return instance
-        except (ValidationError, ValueError) as e:
+        except (ValidationError, ValueError, TypeError, AttributeError) as e:
             error_messages.append(str(e))
         # deserialize data into Dict[str, NestedModel]
         try:
+            data = json.loads(json_str)
             # validation
-            instance.anyof_schema_3_validator = json.loads(json_str)
+            instance.anyof_schema_3_validator = data
             # assign value to actual_instance
             instance.actual_instance = instance.anyof_schema_3_validator
             return instance
-        except (ValidationError, ValueError) as e:
+        except (ValidationError, ValueError, TypeError, AttributeError) as e:
             error_messages.append(str(e))
         # deserialize data into str
         try:

samples/client/others/python-legacy-model-dictionaries/legacy_model_dict_client/models/one_of_model.py

@@ -182,21 +182,23 @@ def from_json(cls, json_str: str) -> Self:
             error_messages.append(str(e))
         # deserialize data into List[NestedModel]
         try:
+            data = json.loads(json_str)
             # validation
-            instance.oneof_schema_2_validator = json.loads(json_str)
+            instance.oneof_schema_2_validator = data
             # assign value to actual_instance
             instance.actual_instance = instance.oneof_schema_2_validator
             match += 1
-        except (ValidationError, ValueError) as e:
+        except (ValidationError, ValueError, TypeError, AttributeError) as e:
             error_messages.append(str(e))
         # deserialize data into Dict[str, NestedModel]
         try:
+            data = json.loads(json_str)
             # validation
-            instance.oneof_schema_3_validator = json.loads(json_str)
+            instance.oneof_schema_3_validator = data
             # assign value to actual_instance
             instance.actual_instance = instance.oneof_schema_3_validator
             match += 1
-        except (ValidationError, ValueError) as e:
+        except (ValidationError, ValueError, TypeError, AttributeError) as e:
             error_messages.append(str(e))
         # deserialize data into str
         try:

samples/openapi3/client/petstore/python-aiohttp/.openapi-generator/FILES

@@ -12,6 +12,7 @@ docs/AllOfWithSingleRef.md
 docs/Animal.md
 docs/AnotherFakeApi.md
 docs/AnyOfColor.md
+docs/AnyOfContainer.md
 docs/AnyOfPig.md
 docs/ArrayOfArrayOfModel.md
 docs/ArrayOfArrayOfNumberOnly.md
@@ -74,11 +75,13 @@ docs/ModelField.md
 docs/ModelReturn.md
 docs/MultiArrays.md
 docs/Name.md
+docs/NestedUnionContainer.md
 docs/NullableClass.md
 docs/NullableProperty.md
 docs/NumberOnly.md
 docs/ObjectToTestAdditionalProperties.md
 docs/ObjectWithDeprecatedFields.md
+docs/OneOfContainer.md
 docs/OneOfEnumString.md
 docs/Order.md
 docs/OuterComposite.md
@@ -149,6 +152,7 @@ petstore_api/models/all_of_super_model.py
 petstore_api/models/all_of_with_single_ref.py
 petstore_api/models/animal.py
 petstore_api/models/any_of_color.py
+petstore_api/models/any_of_container.py
 petstore_api/models/any_of_pig.py
 petstore_api/models/array_of_array_of_model.py
 petstore_api/models/array_of_array_of_number_only.py
@@ -207,11 +211,13 @@ petstore_api/models/model_field.py
 petstore_api/models/model_return.py
 petstore_api/models/multi_arrays.py
 petstore_api/models/name.py
+petstore_api/models/nested_union_container.py
 petstore_api/models/nullable_class.py
 petstore_api/models/nullable_property.py
 petstore_api/models/number_only.py
 petstore_api/models/object_to_test_additional_properties.py
 petstore_api/models/object_with_deprecated_fields.py
+petstore_api/models/one_of_container.py
 petstore_api/models/one_of_enum_string.py
 petstore_api/models/order.py
 petstore_api/models/outer_composite.py

samples/openapi3/client/petstore/python-aiohttp/README.md

@@ -186,6 +186,7 @@ Class | Method | HTTP request | Description
  - [AllOfWithSingleRef](docs/AllOfWithSingleRef.md)
  - [Animal](docs/Animal.md)
  - [AnyOfColor](docs/AnyOfColor.md)
+ - [AnyOfContainer](docs/AnyOfContainer.md)
  - [AnyOfPig](docs/AnyOfPig.md)
  - [ArrayOfArrayOfModel](docs/ArrayOfArrayOfModel.md)
  - [ArrayOfArrayOfNumberOnly](docs/ArrayOfArrayOfNumberOnly.md)
@@ -244,11 +245,13 @@ Class | Method | HTTP request | Description
  - [ModelReturn](docs/ModelReturn.md)
  - [MultiArrays](docs/MultiArrays.md)
  - [Name](docs/Name.md)
+ - [NestedUnionContainer](docs/NestedUnionContainer.md)
  - [NullableClass](docs/NullableClass.md)
  - [NullableProperty](docs/NullableProperty.md)
  - [NumberOnly](docs/NumberOnly.md)
  - [ObjectToTestAdditionalProperties](docs/ObjectToTestAdditionalProperties.md)
  - [ObjectWithDeprecatedFields](docs/ObjectWithDeprecatedFields.md)
+ - [OneOfContainer](docs/OneOfContainer.md)
  - [OneOfEnumString](docs/OneOfEnumString.md)
  - [Order](docs/Order.md)
  - [OuterComposite](docs/OuterComposite.md)