Only publish openapi for structural schemas

staging/src/k8s.io/apiextensions-apiserver/pkg/apiserver/customresource_handler.go

@@ -1236,7 +1236,7 @@ func buildOpenAPIModelsForApply(staticOpenAPISpec *spec.Swagger, crd *apiextensi
 
 	specs := []*spec.Swagger{}
 	for _, v := range crd.Spec.Versions {
-		s, err := builder.BuildSwagger(crd, v.Name, builder.Options{V2: false, StripDefaults: true, StripValueValidation: true})
+		s, err := builder.BuildSwagger(crd, v.Name, builder.Options{V2: false, StripDefaults: true, StripValueValidation: true, AllowNonStructural: true})
 		if err != nil {
 			return nil, err
 		}

staging/src/k8s.io/apiextensions-apiserver/pkg/controller/openapi/builder/builder.go

@@ -75,6 +75,9 @@ type Options struct {
 
 	// Strip value validation.
 	StripValueValidation bool
+
+	// AllowNonStructural indicates swagger should be built for a schema that fits into the structural type but does not meet all structural invariants
+	AllowNonStructural bool
 }
 
 // BuildSwagger builds swagger for the given crd in the given version
@@ -88,17 +91,19 @@ func BuildSwagger(crd *apiextensions.CustomResourceDefinition, version string, o
 	if s != nil && s.OpenAPIV3Schema != nil {
 		if !validation.SchemaHasInvalidTypes(s.OpenAPIV3Schema) {
 			if ss, err := structuralschema.NewStructural(s.OpenAPIV3Schema); err == nil {
-				// skip non-structural schemas
-				schema = ss
+				// skip non-structural schemas unless explicitly asked to produce swagger from them
+				if opts.AllowNonStructural || len(structuralschema.ValidateStructural(nil, ss)) == 0 {
+					schema = ss
 
-				if opts.StripDefaults {
-					schema = schema.StripDefaults()
-				}
-				if opts.StripValueValidation {
-					schema = schema.StripValueValidations()
-				}
+					if opts.StripDefaults {
+						schema = schema.StripDefaults()
+					}
+					if opts.StripValueValidation {
+						schema = schema.StripValueValidations()
+					}
 
-				schema = schema.Unfold()
+					schema = schema.Unfold()
+				}
 			}
 		}
 	}

staging/src/k8s.io/apiextensions-apiserver/pkg/controller/openapi/builder/builder_test.go

@@ -582,6 +582,13 @@ func TestBuildSwagger(t *testing.T) {
 			`{"type":"object","x-kubernetes-group-version-kind":[{"group":"bar.k8s.io","kind":"Foo","version":"v1"}]}`,
 			Options{V2: true, StripDefaults: true},
 		},
+		{
+			"with non-structural schema",
+			`{"type":"object","properties":{"foo":{"type":"array"}}}`,
+			nil,
+			`{"type":"object","x-kubernetes-group-version-kind":[{"group":"bar.k8s.io","kind":"Foo","version":"v1"}]}`,
+			Options{V2: true, StripDefaults: true},
+		},
 		{
 			"with spec.preseveUnknownFields=true",
 			`{"type":"object","properties":{"foo":{"type":"string"}}}`,

test/integration/master/BUILD

@@ -70,6 +70,7 @@ go_test(
         "//vendor/github.com/evanphx/json-patch:go_default_library",
         "//vendor/github.com/go-openapi/spec:go_default_library",
         "//vendor/github.com/stretchr/testify/require:go_default_library",
+        "//vendor/k8s.io/utils/pointer:go_default_library",
         "//vendor/sigs.k8s.io/yaml:go_default_library",
     ] + select({
         "@io_bazel_rules_go//go/platform:android": [

test/integration/master/crd_test.go

@@ -37,6 +37,7 @@ import (
 	kubeapiservertesting "k8s.io/kubernetes/cmd/kube-apiserver/app/testing"
 	"k8s.io/kubernetes/test/integration/etcd"
 	"k8s.io/kubernetes/test/integration/framework"
+	utilpointer "k8s.io/utils/pointer"
 )
 
 func TestCRDShadowGroup(t *testing.T) {
@@ -172,6 +173,7 @@ func TestCRDOpenAPI(t *testing.T) {
 				Plural: "foos",
 				Kind:   "Foo",
 			},
+			PreserveUnknownFields: utilpointer.BoolPtr(false),
 			Validation: &apiextensionsv1beta1.CustomResourceValidation{
 				OpenAPIV3Schema: &apiextensionsv1beta1.JSONSchemaProps{
 					Type: "object",