requestBody with oneOf does not generate marshal/unmarshal union data

[l0n3star]

Minimal yaml:

openapi: 3.0.2
info:
  title: test API
servers:
  - url: 'https://api.server.com'
paths:
  '/command':
    get:
      summary: command summary
      requestBody:
        content:
          application/json:
            schema:
              oneOf:
                - $ref: '#/components/schemas/CommandRequest1'
                - $ref: '#/components/schemas/CommandRequest2'
      responses:
        '200':
          description: OK
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/CommandResponse'

components:
  schemas:
    CommandRequest1:
      type: object
      required:
        - id
      properties:
        id:
          type: string
    CommandRequest2:
      type: object
      required:
        - groupID
      properties:
        groupID:
          type: string
    CommandResponse:
      type: object
      required:
        - command
      properties:
        command:
          type: string

This is the generated go code:

package oapi

import (
	"encoding/json"
)

// CommandRequest1 defines model for CommandRequest1.
type CommandRequest1 struct {
	Id string `json:"id"`
}

// CommandRequest2 defines model for CommandRequest2.
type CommandRequest2 struct {
	GroupID string `json:"groupID"`
}

// CommandResponse defines model for CommandResponse.
type CommandResponse struct {
	Command string `json:"command"`
}

// GetCommandJSONBody defines parameters for GetCommand.
type GetCommandJSONBody struct {
	union json.RawMessage
}

// GetCommandJSONRequestBody defines body for GetCommand for application/json ContentType.
type GetCommandJSONRequestBody GetCommandJSONBody

There is GetCommandJSONBody struct with union data but no functions to use it.

[stefanmcshane]

Also seeing this, which is a hard blocker. Using strict server also

[freshteapot]

For what its worth,

I had a similiar problem, but not on all endpoints.
If you create a higher level object, with a discriminator, it will happily make the union.

But that would require a discriminator the above example, doesnt seem to have that.

[mromaszewicz]

PR #2348 ('Overhaul anonymous schema hoisting', merged 2026-04-29) fixed this by including operation-derived type definitions in the boilerplate passes that emit union accessors. A repro using the exact spec from the issue now generates AsCommandRequest1, FromCommandRequest1, MergeCommandRequest1 (and *2 variants) plus MarshalJSON/UnmarshalJSON on GetCommandJSONBody. The fix is tested by TestBodyRootOneOf_RoundTripCat in internal/test/anonymous_inner_hoisting/client_test.go.

Closing as fixed. If you can still reproduce on a recent release, please reopen with the exact spec and version used.