optional nullable field does not get omitempty json tag as mention in Readme

[damnOblivious]

Readme states that by default nullable fields get omitempty tag. See https://github.com/oapi-codegen/oapi-codegen?tab=readme-ov-file#generating-nullable-types. But that doesn't seem to be the case.

#[0]$ cat config.yaml2
package: preferskipoptionalpointerwithomitzero
output: gen.go
generate:
  models: true
output-options:
  skip-prune: true

#[0]$ cat spec.yaml2
openapi: "3.0.0"
info:
  version: 1.0.0
  title: testing
components:
  schemas:
    ClientWithExtension:
      type: object
      properties:
        newfield:
          type: string
          nullable: true

#[0]$ oapi-codegen --config config.yaml2 spec.yaml2

#[0]$ cat gen.go
// Package preferskipoptionalpointerwithomitzero provides primitives to interact with the openapi HTTP API.
//
// Code generated by github.com/oapi-codegen/oapi-codegen/v2 version v2.5.0 DO NOT EDIT.
package preferskipoptionalpointerwithomitzero

// ClientWithExtension defines model for ClientWithExtension.
type ClientWithExtension struct {
        Newfield *string `json:"newfield"`
}

#[0]$ oapi-codegen --version
github.com/oapi-codegen/oapi-codegen/v2/cmd/oapi-codegen
v2.5.0

#[0]$ go version
go version go1.24.4 linux/amd64

[timharek]

We have the same issue. Our temporary solution is to use overlay for the time being:

  - target: "$.components.schemas.*.properties..[?(@.nullable)]"
    description: Ensure that nullable fields, results in omitempty
    update:
      x-omitempty: true

[jamietanna]

Huh, thanks! Looks like this behaviour hasn't been true at least as far as back as v2.2.0, so could be we documented this incorrectly 🫣

[jamietanna]

Looking at https://github.com/oapi-codegen/oapi-codegen/blob/3eff0a25e492a714ea0b2d8508c59fd898881fd0/pkg/codegen/schema.go#L730 this is expected to not be the case (I'll try and work out whether the docs or the behaviour are wrong)