Support OpenAPI 3.x sum types (oneOf, anyOf, allOf) #3
Description
OpenAPI 3.x sum types (oneOf, anyOf, allOf) are not implemented in ogen, preventing code generation for modern API specs that use polymorphic types. This is a core OpenAPI 3.x feature.
Specs Affected
- carriers/dpd_germany/specs/openapi.yaml (uses
oneOffor shipment types)
Current Error
Feature "sum type parameter" is not implemented yet.
Try to create ogen.yml with:
generator:
ignore_not_implemented: ["sum type parameter"]
to skip unsupported operations.
Example OpenAPI Spec
components:
schemas:
Shipment:
oneOf:
- $ref: '#/components/schemas/DomesticShipment'
- $ref: '#/components/schemas/InternationalShipment'
discriminator:
propertyName: shipmentTypeMinimal Reproduction
openapi: 3.0.1
info:
title: Sum Types Test
version: 1.0.0
paths:
/shipment:
post:
operationId: createShipment
requestBody:
required: true
content:
application/json:
schema:
$ref: '#/components/schemas/Shipment'
responses:
'201':
description: Created
content:
application/json:
schema:
$ref: '#/components/schemas/Shipment'
components:
schemas:
Shipment:
oneOf:
- $ref: '#/components/schemas/DomesticShipment'
- $ref: '#/components/schemas/InternationalShipment'
DomesticShipment:
type: object
properties:
type:
type: string
enum: [domestic]
zipCode:
type: string
InternationalShipment:
type: object
properties:
type:
type: string
enum: [international]
country:
type: stringTest: ogen --target /tmp/test --clean test.yaml
Proposed Solution
Generate Go interfaces or use type unions (Go 1.18+ generics):
// Option 1: Interface-based
type Shipment interface {
isShipment()
}
type DomesticShipment struct { ... }
func (DomesticShipment) isShipment() {}
type InternationalShipment struct { ... }
func (InternationalShipment) isShipment() {}
// Option 2: Union type (Go 1.18+)
type Shipment = DomesticShipment | InternationalShipmentExpected
Generate Go code using interfaces or type unions for sum types
Actual
Generation fails unless operation is skipped
Impact
- Cannot generate clients for APIs using polymorphic types
- Very common pattern in modern REST APIs (different response types, error unions, etc.)
- Workaround requires manual type handling
OpenAPI Spec Reference
- https://spec.openapis.org/oas/v3.0.3#composition-and-inheritance-polymorphism
- https://swagger.io/docs/specification/data-models/oneof-anyof-allof-not/
Related
Similar feature in other generators: oapi-codegen has interfaces for oneOf