feat: Support maxItems validation

staging/src/k8s.io/apimachinery/pkg/api/validate/schema.go

@@ -72,3 +72,11 @@ func Optional[T comparable](_ operation.Context, fldPath *field.Path, value, _ *
 	}
 	return field.ErrorList{field.Required(fldPath, "optional value was not specified")}
 }
+
+// MaxItems verifies that the specified slice is not longer than max items.
+func MaxItems[T any](_ operation.Context, fldPath *field.Path, value, _ []T, max int) field.ErrorList {
+	if len(value) > max {
+		return field.ErrorList{field.TooMany(fldPath, len(value), max)}
+	}
+	return nil
+}

staging/src/k8s.io/code-generator/cmd/validation-gen/output_tests/maxitems/doc.go

@@ -0,0 +1,206 @@
+/*
+Copyright 2024 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+// +k8s:validation-gen=TypeMeta
+// +k8s:validation-gen-scheme-registry=k8s.io/code-generator/cmd/validation-gen/testscheme.Scheme
+
+// This is a test package.
+package maxitems
+
+import "k8s.io/code-generator/cmd/validation-gen/testscheme"
+
+var localSchemeBuilder = testscheme.New()
+
+// Maxitems
+type M struct {
+	TypeMeta int
+
+	// slice-of-primitive
+	// +k8s:validation:maxItems=1
+	M0 []int `json:"m0"`
+
+	// typedef-of-slice-of-primitive
+	// Validation on type only.
+	M1 IntSliceLimited `json:"m1"`
+	// Validation on field only.
+	// +k8s:validation:maxItems=1
+	M2 IntSlice `json:"m2"`
+	// Validation on both type and field.
+	// +k8s:validation:maxItems=2
+	M3 IntSliceLimited `json:"m3"`
+
+	// pointers to slice-of-primitive
+	// Validation on field only.
+
+	// +k8s:validation:maxItems=1
+	M4 *[]int `json:"m4"`
+
+	// pointers to typedef-of-slice-of-primitive
+	// Validation on type only
+	M5 *IntSliceLimited `json:"m5"`
+	// Validation on field only.
+	// +k8s:validation:maxItems=1
+	M6 *IntSlice `json:"m6"`
+	// Validation on both type and field.
+	// +k8s:validation:maxItems=1
+	M7 *IntSliceLimited `json:"m7"`
+
+	// slice-of-pointer-to-primitive
+	// Validation on field only.
+	// +k8s:validation:maxItems=1
+	M8 []*int `json:"m8"`
+
+	// typedef-of-slice-of-pointer-to-primitive
+	// Validation on type only.
+	M9 IntPtrSliceLimited `json:"m9"`
+	// Validation on field only.
+	// +k8s:validation:maxItems=1
+	M10 IntPtrSlice `json:"m10"`
+	// Validation on both type and field.
+	// +k8s:validation:maxItems=1
+	M11 IntPtrSliceLimited `json:"m11"`
+
+	// pointers to slice-of-pointer-to-primitive
+	// Validation on field only.
+	// +k8s:validation:maxItems=1
+	M12 *[]*int `json:"m12"`
+
+	// pointers to typedef-of-slice-of-pointer-to-primitive
+	// Validation on type only.
+	M13 *IntPtrSliceLimited `json:"m13"`
+	// Validation on field only.
+	// +k8s:validation:maxItems=1
+	M14 *IntPtrSlice `json:"m14"`
+	// Validation on both type and field.
+	// +k8s:validation:maxItems=1
+	M15 *IntPtrSliceLimited `json:"m15"`
+
+	// slice-of-struct
+	// +k8s:validation:maxItems=1
+	M16 []S `json:"m16"`
+
+	// typedef-of-slice-of-struct
+	// Validation on type only.
+	M17 SSliceLimited `json:"m17"`
+	// Validation on field only.
+	// +k8s:validation:maxItems=1
+	M18 SSlice `json:"m18"`
+	// Validation on both type and field.
+	// +k8s:validation:maxItems=1
+	M19 SSliceLimited `json:"m19"`
+
+	// pointers to slice-of-struct
+	// Validation on type only.
+	M20 *[]SSliceLimited `json:"m20"`
+	// Validation on field only.
+	// +k8s:validation:maxItems=1
+	M21 *[]SSlice `json:"m21"`
+	// Validation on both type and field.
+	// +k8s:validation:maxItems=1
+	M22 *[]SSliceLimited `json:"m22"`
+
+	// pointers to typedef-of-slice-of-struct
+	// Validation on type only.
+	M23 *SSliceLimited `json:"m23"`
+	// Validation on field only.
+	// +k8s:validation:maxItems=1
+	M24 *SSlice `json:"m24"`
+	// Validation on both type and field.
+	// +k8s:validation:maxItems=1
+	M25 *SSliceLimited `json:"m25"`
+
+	// slice-of-pointer-to-struct
+	// +k8s:validation:maxItems=1
+	M26 []*S `json:"m26"`
+
+	// typedef-of-slice-of-pointer-to-struct
+	// Validation on type only.
+	M27 SPtrSliceLimited `json:"m27"`
+	// Validation on field only.
+	// +k8s:validation:maxItems=1
+	M28 SPtrSlice `json:"m28"`
+	// Validation on both type and field.
+	// +k8s:validation:maxItems=1
+	M29 SPtrSliceLimited `json:"m29"`
+
+	// pointers to slice-of-pointer-to-struct
+	// +k8s:validation:maxItems=1
+	M30 *[]*S `json:"m30"`
+
+	// pointers to typedef-of-slice-of-pointer-to-struct
+	// Validation on type only.
+	M31 *SPtrSliceLimited `json:"m31"`
+	// Validation on field only.
+	// +k8s:validation:maxItems=1
+	M32 *SPtrSlice `json:"m32"`
+	// Validation on both type and field.
+	// +k8s:validation:maxItems=1
+	M33 *SPtrSliceLimited `json:"m33"`
+
+	// slice-of-slice-of-value
+	// +k8s:validation:maxItems=1
+	M34 [][]int `json:"m34"`
+
+	// slice-of-typedef-of-slice-of-value
+	// Validation on type only.
+	M36 []IntSliceLimited `json:"m36"`
+	// Validation on field only.
+	// +k8s:validation:maxItems=1
+	M35 []IntSlice `json:"m35"`
+	// Validation on both type and field.
+	// +k8s:validation:maxItems=1
+	M37 []IntSliceLimited `json:"m37"`
+
+	// slice-of-slice-of-pointer
+	// +k8s:validation:maxItems=1
+	M38 [][]*int `json:"m38"`
+
+	// slice-of-typedef-of-slice-of-pointer
+	// Validation on field only.
+	// +k8s:validation:maxItems=1
+	M39 []IntPtrSlice `json:"m39"`
+	// Validation on type only.
+	M40 []IntPtrSliceLimited `json:"m40"`
+	// Validation on both type and field.
+	// +k8s:validation:maxItems=1
+	M41 []IntPtrSliceLimited `json:"m41"`
+}
+
+// Note: no limit here
+type IntSlice []int
+
+// +k8s:validation:maxItems=2
+type IntSliceLimited []int
+
+// Note: no limit here
+type IntPtrSlice []*int
+
+// +k8s:validation:maxItems=2
+type IntPtrSliceLimited []*int
+
+type S struct{}
+
+// Note: no limit here
+type SSlice []S
+
+// +k8s:validation:maxItems=2
+type SSliceLimited []S
+
+// +k8s:validation:maxItems=2
+type SPtrSliceLimited []*S
+
+// Note: no limit here
+type SPtrSlice []*S

staging/src/k8s.io/code-generator/cmd/validation-gen/output_tests/maxitems/docs_test.go

@@ -0,0 +1,29 @@
+/*
+Copyright 2024 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package maxitems
+
+import (
+	"testing"
+	// "k8s.io/apimachinery/pkg/util/validation/field"
+)
+
+func Test(t *testing.T) {
+	st := localSchemeBuilder.Test(t)
+
+	// Testing M0
+	st.Value(&M{M0: []int{1}, M4: &[]int{1}}).ExpectValid()
+}