Reword missing API error to mention client update

pkg/errors/errors.go

@@ -17,12 +17,15 @@ package errors
 import (
 	"fmt"
 	"strings"
+	"unicode"
+	"unicode/utf8"
 )
 
-func newInvalidCRD(apiGroup string) *KNError {
+func NewInvalidCRD(apiGroup string) *KNError {
 	parts := strings.Split(apiGroup, ".")
 	name := parts[0]
-	msg := fmt.Sprintf("no Knative %s API found on the backend, please verify the installation", name)
+	msg := fmt.Sprintf("no Knative %s API found on the backend, please verify the installation or "+
+		"update the 'kn' client to latest version", firstCharToUpper(name))
 	return NewKNError(msg)
 }
 
@@ -37,3 +40,11 @@ func newNoRouteToHost(errString string) *KNError {
 func newNoKubeConfig(errString string) *KNError {
 	return NewKNError("no kubeconfig has been provided, please use a valid configuration to connect to the cluster")
 }
+
+func firstCharToUpper(s string) string {
+	if len(s) == 0 {
+		return s
+	}
+	r, n := utf8.DecodeRuneInString(s)
+	return string(unicode.ToUpper(r)) + s[n:]
+}

pkg/errors/errors_test.go

@@ -17,17 +17,18 @@ package errors
 import (
 	"testing"
 
+	"knative.dev/client/pkg/util"
+
 	"gotest.tools/v3/assert"
 )
 
 func TestNewInvalidCRD(t *testing.T) {
-	err := newInvalidCRD("serving.knative.dev")
-	assert.Error(t, err, "no Knative serving API found on the backend, please verify the installation")
-
-	err = newInvalidCRD("eventing")
-	assert.Error(t, err, "no Knative eventing API found on the backend, please verify the installation")
+	err := NewInvalidCRD("serving.knative.dev")
+	assert.Assert(t, util.ContainsAll(err.Error(), "no Knative Serving API found on the backend", "please verify the installation", "update", "'kn'"))
 
-	err = newInvalidCRD("")
-	assert.Error(t, err, "no Knative  API found on the backend, please verify the installation")
+	err = NewInvalidCRD("eventing")
+	assert.Assert(t, util.ContainsAll(err.Error(), "no Knative Eventing API found on the backend", "please verify the installation", "update", "'kn'"))
 
+	err = NewInvalidCRD("")
+	assert.Assert(t, util.ContainsAll(err.Error(), "no Knative  API found on the backend", "please verify the installation", "update", "'kn'"))
 }

pkg/errors/factory.go

@@ -54,7 +54,7 @@ func newStatusError(err error) error {
 	}
 	var knerr *KNError
 	if isCRDError(errAPIStatus) {
-		knerr = newInvalidCRD(errAPIStatus.Status().Details.Group)
+		knerr = NewInvalidCRD(errAPIStatus.Status().Details.Group)
 		knerr.Status = errAPIStatus
 		return knerr
 	}

pkg/errors/factory_test.go

@@ -61,7 +61,7 @@ func TestKnErrorsStatusErrors(t *testing.T) {
 				}
 				return statusError
 			},
-			ExpectedMsg: "no Knative serving API found on the backend, please verify the installation",
+			ExpectedMsg: "no Knative Serving API found on the backend, please verify the installation or update the 'kn' client to latest version",
 			Validate: func(t *testing.T, err error, msg string) {
 				assert.Error(t, err, msg)
 			},

pkg/kn/commands/channel/list_types.go

@@ -17,7 +17,6 @@ package channel
 
 import (
 	"context"
-	"fmt"
 
 	"github.com/spf13/cobra"
 	"k8s.io/apimachinery/pkg/apis/meta/v1/unstructured"
@@ -66,7 +65,7 @@ func NewChannelListTypesCommand(p *commands.KnParams) *cobra.Command {
 				channelListTypes = &unstructured.UnstructuredList{}
 			}
 			if !listTypesFlags.GenericPrintFlags.OutputFlagSpecified() && len(channelListTypes.Items) == 0 {
-				return fmt.Errorf("no channels found on the backend, please verify the installation")
+				return knerrors.NewInvalidCRD("Channels")
 			}
 
 			if channelListTypes.GroupVersionKind().Empty() {

pkg/kn/commands/channel/list_types_test.go

@@ -68,7 +68,7 @@ func TestChannelListTypesNoChannelInstalled(t *testing.T) {
 
 	_, err := channelFakeCmd([]string{"channel", "list-types"}, dynamicClient)
 	assert.Check(t, err != nil)
-	assert.Check(t, util.ContainsAll(err.Error(), "no channels found on the backend, please verify the installation"))
+	assert.Check(t, util.ContainsAll(err.Error(), "no", "Knative Channels", "found", "backend", "verify", "installation"))
 }
 
 func TestChannelListTypesNoChannelWithJsonOutput(t *testing.T) {
@@ -86,7 +86,7 @@ func TestChannelListTypesErrorDynamicClient(t *testing.T) {
 
 	_, err := channelFakeCmd([]string{"channel", "list-types"}, dynamicClient)
 	assert.Check(t, err != nil)
-	assert.Check(t, util.ContainsAll(err.Error(), "no channels found on the backend, please verify the installation"))
+	assert.Check(t, util.ContainsAll(err.Error(), "no", "Knative Channels", "found", "backend", "verify", "installation"))
 }
 
 func TestChannelListTypes(t *testing.T) {

pkg/kn/commands/source/list_test.go

@@ -56,7 +56,7 @@ func sourceFakeCmd(args []string, objects ...runtime.Object) (output []string, e
 func TestSourceListTypesNoSourcesInstalled(t *testing.T) {
 	_, err := sourceFakeCmd([]string{"source", "list-types"})
 	assert.Check(t, err != nil)
-	assert.Check(t, util.ContainsAll(err.Error(), "no sources", "found", "backend", "verify", "installation"))
+	assert.Check(t, util.ContainsAll(err.Error(), "no", "Knative Sources", "found", "backend", "verify", "installation"))
 }
 
 func TestSourceListTypesNoSourcesWithJsonOutput(t *testing.T) {

pkg/kn/commands/source/list_types.go

@@ -16,7 +16,6 @@ package source
 
 import (
 	"context"
-	"fmt"
 
 	"knative.dev/client/pkg/sources"
 
@@ -68,7 +67,7 @@ func NewListTypesCommand(p *commands.KnParams) *cobra.Command {
 			}
 
 			if !listTypesFlags.GenericPrintFlags.OutputFlagSpecified() && len(sourceListTypes.Items) == 0 {
-				return fmt.Errorf("no sources found on the backend, please verify the installation")
+				return knerrors.NewInvalidCRD("Sources")
 			}
 
 			if sourceListTypes.GroupVersionKind().Empty() {