feat(validation-gen): add Enum validator function

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

@@ -0,0 +1,40 @@
+/*
+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 validate
+
+import (
+	"context"
+	"slices"
+
+	"k8s.io/apimachinery/pkg/api/operation"
+	"k8s.io/apimachinery/pkg/util/sets"
+	"k8s.io/apimachinery/pkg/util/validation/field"
+)
+
+// Enum verifies that the specified value is one of the valid symbols.
+// This is for string enums only.
+func Enum[T ~string](_ context.Context, op operation.Operation, fldPath *field.Path, value, _ *T, symbols sets.Set[T]) field.ErrorList {
+	if value == nil {
+		return nil
+	}
+	if !symbols.Has(*value) {
+		symbolList := symbols.UnsortedList()
+		slices.Sort(symbolList)
+		return field.ErrorList{field.NotSupported[T](fldPath, *value, symbolList)}
+	}
+	return nil
+}

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

@@ -0,0 +1,107 @@
+/*
+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 validate
+
+import (
+	"context"
+	"testing"
+
+	"k8s.io/apimachinery/pkg/api/operation"
+	"k8s.io/apimachinery/pkg/util/sets"
+	"k8s.io/apimachinery/pkg/util/validation/field"
+)
+
+func TestEnum(t *testing.T) {
+	cases := []struct {
+		value string
+		valid sets.Set[string]
+		err   bool
+	}{{
+		value: "a",
+		valid: sets.New("a", "b", "c"),
+		err:   false,
+	}, {
+		value: "x",
+		valid: sets.New("c", "a", "b"),
+		err:   true,
+	}}
+
+	for i, tc := range cases {
+		result := Enum(context.Background(), operation.Operation{}, field.NewPath("fldpath"), &tc.value, nil, tc.valid)
+		if len(result) > 0 && !tc.err {
+			t.Errorf("case %d: unexpected failure: %v", i, fmtErrs(result))
+			continue
+		}
+		if len(result) == 0 && tc.err {
+			t.Errorf("case %d: unexpected success", i)
+			continue
+		}
+		if len(result) > 0 {
+			if len(result) > 1 {
+				t.Errorf("case %d: unexepected multi-error: %v", i, fmtErrs(result))
+				continue
+			}
+			if want, got := `supported values: "a", "b", "c"`, result[0].Detail; got != want {
+				t.Errorf("case %d: wrong error, expected: %q, got: %q", i, want, got)
+			}
+		}
+	}
+}
+
+func TestEnumTypedef(t *testing.T) {
+	type StringType string
+	const (
+		NotStringFoo StringType = "foo"
+		NotStringBar StringType = "bar"
+		NotStringQux StringType = "qux"
+	)
+
+	cases := []struct {
+		value StringType
+		valid sets.Set[StringType]
+		err   bool
+	}{{
+		value: "foo",
+		valid: sets.New(NotStringFoo, NotStringBar, NotStringQux),
+		err:   false,
+	}, {
+		value: "x",
+		valid: sets.New(NotStringFoo, NotStringBar, NotStringQux),
+		err:   true,
+	}}
+
+	for i, tc := range cases {
+		result := Enum(context.Background(), operation.Operation{}, field.NewPath("fldpath"), &tc.value, nil, tc.valid)
+		if len(result) > 0 && !tc.err {
+			t.Errorf("case %d: unexpected failure: %v", i, fmtErrs(result))
+			continue
+		}
+		if len(result) == 0 && tc.err {
+			t.Errorf("case %d: unexpected success", i)
+			continue
+		}
+		if len(result) > 0 {
+			if len(result) > 1 {
+				t.Errorf("case %d: unexepected multi-error: %v", i, fmtErrs(result))
+				continue
+			}
+			if want, got := `supported values: "bar", "foo", "qux"`, result[0].Detail; got != want {
+				t.Errorf("case %d: wrong error, expected: %q, got: %q", i, want, got)
+			}
+		}
+	}
+}