validation-gen: add tests for nilable optional fields with defaults

Cover *Struct, []string, and map[string]string with non-zero defaults
in the nonzero_defaults package. Each previously failed code generation
and now emits the expected RequiredPointer/RequiredSlice/RequiredMap
validator.

staging/src/k8s.io/code-generator/cmd/validation-gen/output_tests/tags/optional/nonzero_defaults/doc.go

@@ -51,4 +51,20 @@ type Struct struct {
 	// +k8s:optional
 	// +default=true
 	BoolPtrField *bool `json:"boolPtrField"`
+
+	// +k8s:optional
+	// +default={"name": "x"}
+	StructPtrField *Submarker `json:"structPtrField"`
+
+	// +k8s:optional
+	// +default=["foo"]
+	SliceField []string `json:"sliceField"`
+
+	// +k8s:optional
+	// +default={"k": "v"}
+	MapField map[string]string `json:"mapField"`
+}
+
+type Submarker struct {
+	Name string `json:"name"`
 }

staging/src/k8s.io/code-generator/cmd/validation-gen/output_tests/tags/optional/nonzero_defaults/doc_test.go

@@ -35,6 +35,9 @@ func Test(t *testing.T) {
 		field.Required(field.NewPath("intPtrField"), ""),
 		field.Required(field.NewPath("boolField"), ""),
 		field.Required(field.NewPath("boolPtrField"), ""),
+		field.Required(field.NewPath("structPtrField"), ""),
+		field.Required(field.NewPath("sliceField"), ""),
+		field.Required(field.NewPath("mapField"), ""),
 	})
 
 	st.Value(&Struct{
@@ -44,5 +47,8 @@ func Test(t *testing.T) {
 		IntPtrField:    ptr.To(0),
 		BoolField:      true,
 		BoolPtrField:   ptr.To(false),
+		StructPtrField: &Submarker{Name: "x"},
+		SliceField:     []string{"foo"},
+		MapField:       map[string]string{"k": "v"},
 	}).ExpectValid()
 }

staging/src/k8s.io/code-generator/cmd/validation-gen/output_tests/tags/optional/nonzero_defaults/zz_generated.validations.go

@@ -25,6 +25,7 @@ import (
 	context "context"
 	fmt "fmt"
 
+	equality "k8s.io/apimachinery/pkg/api/equality"
 	operation "k8s.io/apimachinery/pkg/api/operation"
 	safe "k8s.io/apimachinery/pkg/api/safe"
 	validate "k8s.io/apimachinery/pkg/api/validate"
@@ -243,5 +244,95 @@ func Validate_Struct(
 		errs = append(errs, fn(fldPath.Child("boolPtrField"), obj.BoolPtrField, oldVal, oldObj != nil)...)
 	}
 
+	{ // field Struct.StructPtrField
+		fn := func(
+			fldPath *field.Path,
+			obj, oldObj *Submarker,
+			oldValueCorrelated bool) (errs field.ErrorList) {
+			// don't revalidate unchanged data
+			if oldValueCorrelated && op.Type == operation.Update {
+				if obj == oldObj || (obj != nil && oldObj != nil && *obj == *oldObj) {
+					return nil
+				}
+			}
+			// call field-attached validations
+			earlyReturn := false
+			// optional fields with default values are effectively required
+			if e := validate.RequiredPointer(ctx, op, fldPath, obj, oldObj).MarkShortCircuit(); len(e) != 0 {
+				errs = append(errs, e...)
+				earlyReturn = true
+			}
+			if earlyReturn {
+				return // do not proceed
+			}
+			return
+		}
+		oldVal := safe.Field(oldObj,
+			func(oldObj *Struct) *Submarker {
+				return oldObj.StructPtrField
+			})
+		errs = append(errs, fn(fldPath.Child("structPtrField"), obj.StructPtrField, oldVal, oldObj != nil)...)
+	}
+
+	{ // field Struct.SliceField
+		fn := func(
+			fldPath *field.Path,
+			obj, oldObj []string,
+			oldValueCorrelated bool) (errs field.ErrorList) {
+			// don't revalidate unchanged data
+			if oldValueCorrelated && op.Type == operation.Update {
+				if equality.Semantic.DeepEqual(obj, oldObj) {
+					return nil
+				}
+			}
+			// call field-attached validations
+			earlyReturn := false
+			// optional fields with default values are effectively required
+			if e := validate.RequiredSlice(ctx, op, fldPath, obj, oldObj).MarkShortCircuit(); len(e) != 0 {
+				errs = append(errs, e...)
+				earlyReturn = true
+			}
+			if earlyReturn {
+				return // do not proceed
+			}
+			return
+		}
+		oldVal := safe.Field(oldObj,
+			func(oldObj *Struct) []string {
+				return oldObj.SliceField
+			})
+		errs = append(errs, fn(fldPath.Child("sliceField"), obj.SliceField, oldVal, oldObj != nil)...)
+	}
+
+	{ // field Struct.MapField
+		fn := func(
+			fldPath *field.Path,
+			obj, oldObj map[string]string,
+			oldValueCorrelated bool) (errs field.ErrorList) {
+			// don't revalidate unchanged data
+			if oldValueCorrelated && op.Type == operation.Update {
+				if equality.Semantic.DeepEqual(obj, oldObj) {
+					return nil
+				}
+			}
+			// call field-attached validations
+			earlyReturn := false
+			// optional fields with default values are effectively required
+			if e := validate.RequiredMap(ctx, op, fldPath, obj, oldObj).MarkShortCircuit(); len(e) != 0 {
+				errs = append(errs, e...)
+				earlyReturn = true
+			}
+			if earlyReturn {
+				return // do not proceed
+			}
+			return
+		}
+		oldVal := safe.Field(oldObj,
+			func(oldObj *Struct) map[string]string {
+				return oldObj.MapField
+			})
+		errs = append(errs, fn(fldPath.Child("mapField"), obj.MapField, oldVal, oldObj != nil)...)
+	}
+
 	return errs
 }