apiextensions: generalize nullable to arbitrary types

staging/src/k8s.io/apiextensions-apiserver/pkg/apis/apiextensions/fuzzer/fuzzer.go

@@ -20,7 +20,7 @@ import (
 	"reflect"
 	"strings"
 
-	"github.com/google/gofuzz"
+	fuzz "github.com/google/gofuzz"
 
 	"k8s.io/apiextensions-apiserver/pkg/apis/apiextensions"
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
@@ -113,6 +113,9 @@ func Funcs(codecs runtimeserializer.CodecFactory) []interface{} {
 				validRef := "validRef"
 				obj.Ref = &validRef
 			}
+			if len(obj.Type) == 0 {
+				obj.Nullable = false // because this does not roundtrip through go-openapi
+			}
 		},
 		func(obj *apiextensions.JSONSchemaPropsOrBool, c fuzz.Continue) {
 			if c.RandBool() {

staging/src/k8s.io/apiextensions-apiserver/pkg/apis/apiextensions/validation/validation.go

@@ -647,9 +647,6 @@ func (v *specStandardValidatorV3) validate(schema *apiextensions.JSONSchemaProps
 	if schema.Type == "null" {
 		allErrs = append(allErrs, field.Forbidden(fldPath.Child("type"), "type cannot be set to null, use nullable as an alternative"))
 	}
-	if schema.Nullable && schema.Type != "object" && schema.Type != "array" {
-		allErrs = append(allErrs, field.Forbidden(fldPath.Child("nullable"), "nullable can only be set for object and array types"))
-	}
 
 	if schema.Items != nil && len(schema.Items.JSONSchemas) != 0 {
 		allErrs = append(allErrs, field.Forbidden(fldPath.Child("items"), "items must be a schema object and not an array"))

staging/src/k8s.io/apiextensions-apiserver/pkg/apis/apiextensions/validation/validation_test.go

@@ -1259,24 +1259,10 @@ func TestValidateCustomResourceDefinitionValidation(t *testing.T) {
 					},
 				},
 			},
-			wantError: true,
+			wantError: false,
 		},
 		{
-			name: "nullable with wrong type",
+			name: "nullable with types",
-			input: apiextensions.CustomResourceValidation{
-				OpenAPIV3Schema: &apiextensions.JSONSchemaProps{
-					Properties: map[string]apiextensions.JSONSchemaProps{
-						"string": {
-							Type:     "string",
-							Nullable: true,
-						},
-					},
-				},
-			},
-			wantError: true,
-		},
-		{
-			name: "nullable with right types",
 			input: apiextensions.CustomResourceValidation{
 				OpenAPIV3Schema: &apiextensions.JSONSchemaProps{
 					Properties: map[string]apiextensions.JSONSchemaProps{
@@ -1288,6 +1274,14 @@ func TestValidateCustomResourceDefinitionValidation(t *testing.T) {
 							Type:     "array",
 							Nullable: true,
 						},
+						"number": {
+							Type:     "number",
+							Nullable: true,
+						},
+						"string": {
+							Type:     "string",
+							Nullable: true,
+						},
 					},
 				},
 			},

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

@@ -70,10 +70,9 @@ func ConvertJSONSchemaPropsWithPostProcess(in *apiextensions.JSONSchemaProps, ou
 	out.Description = in.Description
 	if in.Type != "" {
 		out.Type = spec.StringOrArray([]string{in.Type})
-	}
+		if in.Nullable {
-	if in.Nullable {
+			out.Type = append(out.Type, "null")
-		// by validation, in.Type is either "object" or "array"
+		}
-		out.Type = append(out.Type, "null")
 	}
 	out.Format = in.Format
 	out.Title = in.Title

staging/src/k8s.io/apiextensions-apiserver/pkg/apiserver/validation/validation_test.go

@@ -46,6 +46,7 @@ func TestRoundTrip(t *testing.T) {
 	}
 
 	seed := rand.Int63()
+	t.Logf("seed: %d", seed)
 	fuzzerFuncs := fuzzer.MergeFuzzerFuncs(apiextensionsfuzzer.Funcs)
 	f := fuzzer.FuzzerFor(fuzzerFuncs, rand.NewSource(seed), codecs)
 
@@ -90,7 +91,7 @@ func TestRoundTrip(t *testing.T) {
 		}
 
 		if !apiequality.Semantic.DeepEqual(internal, internalRoundTripped) {
-			t.Fatalf("expected\n\t%#v, got \n\t%#v", internal, internalRoundTripped)
+			t.Fatalf("%d: expected\n\t%#v, got \n\t%#v", i, internal, internalRoundTripped)
 		}
 	}
 }
@@ -214,6 +215,26 @@ func TestNullable(t *testing.T) {
 			},
 			map[string]interface{}{},
 		}, false},
+		{"nullable and no type against non-nil", args{
+			apiextensions.JSONSchemaProps{
+				Properties: map[string]apiextensions.JSONSchemaProps{
+					"field": {
+						Nullable: true,
+					},
+				},
+			},
+			map[string]interface{}{"field": 42},
+		}, false},
+		{"nullable and no type against nil", args{
+			apiextensions.JSONSchemaProps{
+				Properties: map[string]apiextensions.JSONSchemaProps{
+					"field": {
+						Nullable: true,
+					},
+				},
+			},
+			map[string]interface{}{"field": nil},
+		}, false},
 	}
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {