enhance error message on no current context

Author: SimonTheLeg

cmd/api-syncagent/main.go

@@ -22,7 +22,6 @@ import (
 	"fmt"
 	golog "log"
 	"slices"
-	"strings"
 
 	"github.com/go-logr/zapr"
 	"github.com/spf13/pflag"
@@ -32,6 +31,7 @@ import (
 	"github.com/kcp-dev/api-syncagent/internal/controller/apiexport"
 	"github.com/kcp-dev/api-syncagent/internal/controller/apiresourceschema"
 	"github.com/kcp-dev/api-syncagent/internal/controller/syncmanager"
+	"github.com/kcp-dev/api-syncagent/internal/kubeconfig"
 	syncagentlog "github.com/kcp-dev/api-syncagent/internal/log"
 	"github.com/kcp-dev/api-syncagent/internal/version"
 	syncagentv1alpha1 "github.com/kcp-dev/api-syncagent/sdk/apis/syncagent/v1alpha1"
@@ -108,8 +108,8 @@ func run(ctx context.Context, log *zap.SugaredLogger, opts *Options) error {
 	}
 
 	// sanity check
-	if !strings.Contains(kcpRestConfig.Host, "/clusters/") {
-		return fmt.Errorf("kcp kubeconfig does not point to a specific workspace")
+	if err := kubeconfig.Validate(kcpRestConfig); err != nil {
+		return fmt.Errorf("failed to check kcp kubeconfig: %w", err)
 	}
 
 	// We check if the APIExport/APIExportEndpointSlice exists and extract information we need to set up our kcpCluster.

internal/kubeconfig/check.go

@@ -0,0 +1,36 @@
+/*
+Copyright 2025 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 kubeconfig
+
+import (
+	"errors"
+	"strings"
+
+	"k8s.io/client-go/rest"
+)
+
+func Validate(c *rest.Config) error {
+	if c == nil {
+		return errors.New("no kubeconfig was found. Have you set current-context?")
+	}
+
+	if !strings.Contains(c.Host, "/clusters/") {
+		return errors.New("kcp kubeconfig does not point to a specific workspace")
+	}
+
+	return nil
+}

internal/kubeconfig/check_test.go

@@ -0,0 +1,60 @@
+/*
+Copyright 2025 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 kubeconfig
+
+import (
+	"testing"
+
+	"k8s.io/client-go/rest"
+)
+
+func TestValidate(t *testing.T) {
+	tests := []struct {
+		name       string
+		kubeconfig *rest.Config
+		expErr     bool
+	}{
+		{
+			name:       "nil kubeconfig",
+			kubeconfig: nil,
+			expErr:     true,
+		},
+		{
+			name: "kubeconfig without workspace",
+			kubeconfig: &rest.Config{
+				Host: "https://example.com",
+			},
+			expErr: true,
+		},
+		{
+			name: "valid kcp kubeconfig",
+			kubeconfig: &rest.Config{
+				Host: "https://example.com/clusters/foo",
+			},
+			expErr: false,
+		},
+	}
+
+	for _, testcase := range tests {
+		t.Run(testcase.name, func(t *testing.T) {
+			err := Validate(testcase.kubeconfig)
+			if (err != nil) != testcase.expErr {
+				t.Errorf("Expected error %v, got %v", testcase.expErr, err)
+			}
+		})
+	}
+}