ContextValidate panics if the field is nil for discriminator types

[romainbou]

Problem statement

The context validation expects a field to be set and can panic if it's nil. I expect it to skip the validation if it's nil.

Swagger specification

pets.yml

definitions:
  animal:
    type: 'object'
    properties:
      kind:
        $ref: '#/definitions/pet'
  pet:
    type: object
    required: [type]
    discriminator: type
    properties:
      type:
        $ref: '#/definitions/petType'

  petType:
    type: string
    enum:
      - dog
      - cat

  dog:    
    allOf:
      - $ref: '#/definitions/pet'
        type: object
  cat:
    allOf:
      - $ref: '#/definitions/pet'
        type: object

The generated model for animal.go as the following validator since go-swagger v0.27.0

func (m *Animal) contextValidateKind(ctx context.Context, formats strfmt.Registry) error {

	if err := m.Kind().ContextValidate(ctx, formats); err != nil {
// ...

Which panics if m.Kind() == nil

While the check is done in the field's validation

func (m *Animal) validateKind(formats strfmt.Registry) error {
	if swag.IsZero(m.Kind()) { // not required
		return nil
	}
// ...

Steps to reproduce

swagger -q generate model \
	 	--accept-definitions-only \
		--model-package=pkg/models_test \
		--target=./ \
		--spec=pets.yml

Go test:

package models_test

import (
	"context"
	"testing"

	"github.com/go-openapi/strfmt"
	"gopkg.in/go-playground/assert.v1"
)

func TestAnimal(t *testing.T) {
	animal := Animal{
		Name: "Fido",
	}
	formats := strfmt.NewFormats()
	err := animal.validateKind(formats)
	assert.Equal(t, nil, err)
	err = animal.contextValidateKind(context.Background(), formats)
	assert.Equal(t, nil, err)
}

The first assert pass, the second panics:

--- FAIL: TestAnimal (0.00s)
panic: runtime error: invalid memory address or nil pointer dereference [recovered]
	panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x18 pc=0x86ba1d]

goroutine 6 [running]:
testing.tRunner.func1.2({0x8c83e0, 0xcd2e70})
	/usr/lib/go/src/testing/testing.go:1526 +0x24e
testing.tRunner.func1()
	/usr/lib/go/src/testing/testing.go:1529 +0x39f
panic({0x8c83e0, 0xcd2e70})
	/usr/lib/go/src/runtime/panic.go:884 +0x213
models_test.(*Animal).contextValidateKind(0xc0000d5d40?, {0x9fc718?, 0xc00002a130?}, {0x9fdcf0?, 0xc0002ae8a0?})
	models_test/animal.go:150 +0x7d
models_test.TestAnimal(0x0?)
	models_test/animal_test.go:23 +0x1cf
testing.tRunner(0xc0000d5d40, 0x97dc68)
	/usr/lib/go/src/testing/testing.go:1576 +0x10b
created by testing.(*T).Run
	/usr/lib/go/src/testing/testing.go:1629 +0x3ea
FAIL	models_test	0.006s

Environment

swagger version: 0.30.4
go version: 1.20
OS: Manjaro Linux 6.1.12

Potential fix

romainbou@76553bf

If this makes sense and doesn't have unforeseen consequences, I can make a PR.

Alternatively, would there be an option to disable contextValidate?
Thanks!

[youyuanwu]

Looks like a valid bug. PR welcome.

[fredbi]

fixed by #2911 merged. Closing.