Address comment: fix and test cluster regex

config/crds/tenancy.kcp.dev_clusterworkspaces.yaml

@@ -54,7 +54,7 @@ spec:
                   - root
                   - org
                   - system
-                pattern: ^[a-z0-9][a-z0-9-]*[a-z0-9]$
+                pattern: ^[a-z]([a-z0-9-]{0,29}[a-z0-9])?$
                 type: string
             type: object
           spec:

config/crds/tenancy.kcp.dev_clusterworkspaces.yaml-patch

@@ -2,7 +2,7 @@
   path: /spec/versions/name=v1alpha1/schema/openAPIV3Schema/properties/metadata/properties
   value:
     name:
-      pattern: "^[a-z0-9][a-z0-9-]*[a-z0-9]$"
+      pattern: "^[a-z]([a-z0-9-]{0,29}[a-z0-9])?$"
       minLength: 1
       maxLength: 31 # half of max name length
       type: string

pkg/server/handler.go

@@ -51,7 +51,7 @@ import (
 )
 
 var (
-	reClusterName = regexp.MustCompile(`^([a-z0-9][a-z0-9-]{0,30}[a-z0-9]:)*[a-z0-9][a-z0-9-]{0,30}[a-z0-9]$`)
+	reClusterName = regexp.MustCompile(`^([a-z]([a-z0-9-]{0,29}[a-z0-9])?:)*[a-z]([a-z0-9-]{0,29}[a-z0-9])?$`)
 
 	errorScheme = runtime.NewScheme()
 	errorCodecs = serializer.NewCodecFactory(errorScheme)

pkg/server/handler_test.go

@@ -0,0 +1,93 @@
+/*
+Copyright 2022 The KCP 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 server
+
+import (
+	"fmt"
+	"io/ioutil"
+	"path/filepath"
+	"runtime"
+	"strings"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+
+	apiextensionsv1 "k8s.io/apiextensions-apiserver/pkg/apis/apiextensions/v1"
+	"sigs.k8s.io/yaml"
+)
+
+func TestClusterWorkspaceNamePattern(t *testing.T) {
+	_, fileName, _, _ := runtime.Caller(0)
+	bs, err := ioutil.ReadFile(filepath.Join(filepath.Dir(fileName), "..", "..", "config/crds/tenancy.kcp.dev_clusterworkspaces.yaml"))
+	require.NoError(t, err)
+	var crd apiextensionsv1.CustomResourceDefinition
+	err = yaml.Unmarshal(bs, &crd)
+	require.NoError(t, err)
+	require.Len(t, crd.Spec.Versions, 1, "crd should have exactly one version, update the test when this changes")
+
+	namePattern := crd.Spec.Versions[0].Schema.OpenAPIV3Schema.Properties["metadata"].Properties["name"].Pattern
+	require.True(t, strings.HasPrefix(namePattern, "^"), "cluster name pattern should end with $")
+	require.True(t, strings.HasSuffix(namePattern, "$"), "cluster name pattern should start with ^")
+
+	namePattern = strings.Trim(namePattern, "^$")
+	require.Equal(t, fmt.Sprintf("^(%s:)*%s$", namePattern, namePattern), reClusterName.String(), "logical cluster regex should match ClusterWorkspace name pattern")
+}
+
+func TestReCluster(t *testing.T) {
+
+	tests := []struct {
+		cluster string
+		valid   bool
+	}{
+		{"", false},
+
+		{"root", true},
+		{"root:foo", true},
+		{"root:foo:bar", true},
+
+		{"system", true},
+		{"system:foo", true},
+		{"system:foo:bar", true},
+
+		{"foo", true},
+		{"foo:bar", true},
+		{"foo:bar-bar", true},
+		{"foo:b", true},
+		{"foo:bar0", true},
+		{"foo:b123456789012345678901234567891", true},
+		{"f", true},
+
+		{"root:", false},
+		{":root", false},
+		{"root::foo", false},
+		{"root:föö:bär", false},
+		{"foo:bar_bar", false},
+		{"foo:0", false},
+		{"foo:0bar", false},
+		{"foo/bar", false},
+		{"foo:bar-", false},
+		{"foo:-bar", false},
+		{"foo:b1234567890123456789012345678912", false},
+	}
+	for _, tt := range tests {
+		t.Run(tt.cluster, func(t *testing.T) {
+			if got := reClusterName.MatchString(tt.cluster); got != tt.valid {
+				t.Errorf("reCluster.MatchString(%q) = %v, want %v", tt.cluster, got, tt.valid)
+			}
+		})
+	}
+}