List inbuilt sources if CRD access is restricted

 Fixes knative#947
 - Identify restricted access error
 - If server returns restricted access error, fallback to listing
   only eventing inbuilt sources using their GVKs.
 - List any inbuilt source (ApiServerSource) object and read the error
   to know if eventing is installed for `kn source list-types`.

pkg/dynamic/client.go

@@ -15,6 +15,8 @@
 package dynamic
 
 import (
+	"strings"
+
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 	"k8s.io/apimachinery/pkg/apis/meta/v1/unstructured"
 	"k8s.io/apimachinery/pkg/labels"
@@ -48,6 +50,9 @@ type KnDynamicClient interface {
 	// ListSources returns list of available source objects
 	ListSources(types ...WithType) (*unstructured.UnstructuredList, error)
 
+	// ListSources returns list of available source objects using given list of GVKs
+	ListSourcesUsingGVKs(*[]schema.GroupVersionKind, ...WithType) (*unstructured.UnstructuredList, error)
+
 	// RawClient returns the raw dynamic client interface
 	RawClient() dynamic.Interface
 }
@@ -107,7 +112,7 @@ func (c *knDynamicClient) ListSources(types ...WithType) (*unstructured.Unstruct
 	var (
 		sourceList               unstructured.UnstructuredList
 		options                  metav1.ListOptions
-		numberOfsourceTypesFound int
+		numberOfSourceTypesFound int
 	)
 	sourceTypes, err := c.ListSourcesTypes()
 	if err != nil {
@@ -141,14 +146,56 @@ func (c *knDynamicClient) ListSources(types ...WithType) (*unstructured.Unstruct
 
 		if len(sList.Items) > 0 {
 			// keep a track if we found source objects of different types
-			numberOfsourceTypesFound++
+			numberOfSourceTypesFound++
+			sourceList.Items = append(sourceList.Items, sList.Items...)
+			sourceList.SetGroupVersionKind(sList.GetObjectKind().GroupVersionKind())
+		}
+	}
+	// Clear the Group and Version for list if there are multiple types of source objects found
+	// Keep the source's GVK if there is only one type of source objects found or requested via --type filter
+	if numberOfSourceTypesFound > 1 {
+		sourceList.SetGroupVersionKind(schema.GroupVersionKind{Group: "", Version: "", Kind: "List"})
+	}
+	return &sourceList, nil
+}
+
+// ListSources returns list of available source objects using given list of GVKs
+func (c *knDynamicClient) ListSourcesUsingGVKs(gvks *[]schema.GroupVersionKind, types ...WithType) (*unstructured.UnstructuredList, error) {
+	if gvks == nil {
+		return nil, nil
+	}
+
+	var (
+		sourceList               unstructured.UnstructuredList
+		options                  metav1.ListOptions
+		numberOfSourceTypesFound int
+	)
+	namespace := c.Namespace()
+	filters := WithTypes(types).List()
+
+	for _, gvk := range *gvks {
+		if len(filters) > 0 && !util.SliceContainsIgnoreCase(filters, gvk.Kind) {
+			continue
+		}
+
+		gvr := gvk.GroupVersion().WithResource(strings.ToLower(gvk.Kind) + "s")
+
+		// list objects of source type with this GVR
+		sList, err := c.client.Resource(gvr).Namespace(namespace).List(options)
+		if err != nil {
+			return nil, err
+		}
+
+		if len(sList.Items) > 0 {
+			// keep a track if we found source objects of different types
+			numberOfSourceTypesFound++
 			sourceList.Items = append(sourceList.Items, sList.Items...)
 			sourceList.SetGroupVersionKind(sList.GetObjectKind().GroupVersionKind())
 		}
 	}
 	// Clear the Group and Version for list if there are multiple types of source objects found
 	// Keep the source's GVK if there is only one type of source objects found or requested via --type filter
-	if numberOfsourceTypesFound > 1 {
+	if numberOfSourceTypesFound > 1 {
 		sourceList.SetGroupVersionKind(schema.GroupVersionKind{Group: "", Version: "", Kind: "List"})
 	}
 	return &sourceList, nil

pkg/dynamic/lib.go

@@ -16,6 +16,7 @@ package dynamic
 
 import (
 	"fmt"
+	"strings"
 
 	"k8s.io/apimachinery/pkg/apis/meta/v1/unstructured"
 	"k8s.io/apimachinery/pkg/runtime/schema"
@@ -123,3 +124,24 @@ func (types WithTypes) List() []string {
 	}
 	return stypes
 }
+
+func UnstructuredCRDFromGVK(gvk schema.GroupVersionKind) *unstructured.Unstructured {
+	name := fmt.Sprintf("%ss.%s", strings.ToLower(gvk.Kind), gvk.Group)
+	plural := fmt.Sprintf("%ss", strings.ToLower(gvk.Kind))
+	u := &unstructured.Unstructured{}
+	u.SetUnstructuredContent(map[string]interface{}{
+		"metadata": map[string]interface{}{
+			"name": name,
+		},
+		"spec": map[string]interface{}{
+			"group":   gvk.Group,
+			"version": gvk.Version,
+			"names": map[string]interface{}{
+				"kind":   gvk.Kind,
+				"plural": plural,
+			},
+		},
+	})
+
+	return u
+}

pkg/errors/errors.go

@@ -22,7 +22,7 @@ import (
 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("404: no Knative %s API found on the backend, please verify the installation", name)
 	return NewKNError(msg)
 }
 
@@ -37,3 +37,7 @@ func newNoRouteToHost(errString string) error {
 func newNoKubeConfig(errString string) error {
 	return NewKNError("no kubeconfig has been provided, please use a valid configuration to connect to the cluster")
 }
+
+func newForbidden(code int32, msg string) *KNError {
+	return NewKNError(fmt.Sprintf("%d: %s", code, msg))
+}

pkg/errors/errors_test.go

@@ -22,12 +22,12 @@ import (
 
 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")
+	assert.Error(t, err, "404: 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")
+	assert.Error(t, err, "404: no Knative eventing API found on the backend, please verify the installation")
 
 	err = newInvalidCRD("")
-	assert.Error(t, err, "no Knative  API found on the backend, please verify the installation")
+	assert.Error(t, err, "404: no Knative  API found on the backend, please verify the installation")
 
 }

pkg/errors/factory.go

@@ -15,6 +15,7 @@
 package errors
 
 import (
+	"net/http"
 	"strings"
 
 	api_errors "k8s.io/apimachinery/pkg/api/errors"
@@ -38,6 +39,10 @@ func isEmptyConfigError(err error) bool {
 	return strings.Contains(err.Error(), "no configuration has been provided")
 }
 
+func IsForbiddenError(status api_errors.APIStatus) bool {
+	return status.Status().Code == http.StatusForbidden
+}
+
 //Retrieves a custom error struct based on the original error APIStatus struct
 //Returns the original error struct in case it can't identify the kind of APIStatus error
 func GetError(err error) error {
@@ -55,11 +60,17 @@ func GetError(err error) error {
 			return err
 		}
 		var knerr *KNError
-		if isCRDError(apiStatus) {
+		switch {
+		case isCRDError(apiStatus):
 			knerr = newInvalidCRD(apiStatus.Status().Details.Group)
 			knerr.Status = apiStatus
 			return knerr
+		case IsForbiddenError(apiStatus):
+			knerr = newForbidden(apiStatus.Status().Code, apiStatus.Status().Message)
+			knerr.Status = apiStatus
+			return knerr
+		default:
+			return err
 		}
-		return err
 	}
 }

pkg/errors/factory_test.go

@@ -48,7 +48,7 @@ func TestKnErrorsStatusErrors(t *testing.T) {
 				}
 				return statusError
 			},
-			ExpectedMsg: "no Knative serving API found on the backend, please verify the installation",
+			ExpectedMsg: "404: no Knative serving API found on the backend, please verify the installation",
 			Validate: func(t *testing.T, err error, msg string) {
 				assert.Error(t, err, msg)
 			},

pkg/kn/commands/source/list.go

@@ -16,13 +16,16 @@ package source
 
 import (
 	"fmt"
+	"strings"
 
 	"github.com/spf13/cobra"
 
 	"knative.dev/client/pkg/dynamic"
+	knerrors "knative.dev/client/pkg/errors"
 	"knative.dev/client/pkg/kn/commands"
 	"knative.dev/client/pkg/kn/commands/flags"
 	"knative.dev/client/pkg/kn/commands/source/duck"
+	sourcesv1alpha2 "knative.dev/client/pkg/sources/v1alpha2"
 )
 
 var listExample = `
@@ -58,8 +61,15 @@ func NewListCommand(p *commands.KnParams) *cobra.Command {
 			}
 			sourceList, err := dynamicClient.ListSources(filters...)
 			if err != nil {
-				return err
+				if strings.HasPrefix(knerrors.GetError(err).Error(), "403") {
+					gvks := sourcesv1alpha2.BuiltInSourcesGVKs()
+					sourceList, err = dynamicClient.ListSourcesUsingGVKs(&gvks, filters...)
+					if err != nil {
+						return knerrors.GetError(err)
+					}
+				}
 			}
+
 			if len(sourceList.Items) == 0 {
 				fmt.Fprintf(cmd.OutOrStdout(), "No sources found in %s namespace.\n", namespace)
 				return nil

pkg/kn/commands/source/list_types.go

@@ -16,11 +16,16 @@ package source
 
 import (
 	"fmt"
+	"strings"
 
 	"github.com/spf13/cobra"
 
+	"k8s.io/apimachinery/pkg/apis/meta/v1/unstructured"
+	"knative.dev/client/pkg/dynamic"
+	knerrors "knative.dev/client/pkg/errors"
 	"knative.dev/client/pkg/kn/commands"
 	"knative.dev/client/pkg/kn/commands/flags"
+	sourcesv1alpha2 "knative.dev/client/pkg/sources/v1alpha2"
 )
 
 // NewListTypesCommand defines and processes `kn source list-types`
@@ -48,11 +53,21 @@ func NewListTypesCommand(p *commands.KnParams) *cobra.Command {
 
 			sourceListTypes, err := dynamicClient.ListSourcesTypes()
 			if err != nil {
-				return err
+				if strings.HasPrefix(knerrors.GetError(err).Error(), "403") {
+					sourcesClient, err := p.NewSourcesClient(namespace)
+					if err != nil {
+						return err
+					}
+
+					sourceListTypes, err = listBuiltInSourceTypes(sourcesClient)
+					if err != nil {
+						return knerrors.GetError(err)
+					}
+				}
 			}
 
 			if len(sourceListTypes.Items) == 0 {
-				fmt.Fprintf(cmd.OutOrStdout(), "No sources found.\n")
+				fmt.Fprintf(cmd.OutOrStdout(), "404: no sources found on the backend, please verify the installation\n")
 				return nil
 			}
 
@@ -73,3 +88,20 @@ func NewListTypesCommand(p *commands.KnParams) *cobra.Command {
 	listTypesFlags.AddFlags(listTypesCommand)
 	return listTypesCommand
 }
+
+func listBuiltInSourceTypes(c sourcesv1alpha2.KnSourcesClient) (*unstructured.UnstructuredList, error) {
+	_, err := c.APIServerSourcesClient().ListAPIServerSource()
+	if err != nil {
+		if strings.HasPrefix(err.Error(), "404") {
+			return nil, err
+		}
+	}
+
+	uList := unstructured.UnstructuredList{}
+	gvks := sourcesv1alpha2.BuiltInSourcesGVKs()
+	for _, gvk := range gvks {
+		u := dynamic.UnstructuredCRDFromGVK(gvk)
+		uList.Items = append(uList.Items, *u)
+	}
+	return &uList, nil
+}

pkg/sources/v1alpha2/apiserver_client.go

@@ -111,7 +111,7 @@ func (c *apiServerSourcesClient) Namespace() string {
 func (c *apiServerSourcesClient) ListAPIServerSource() (*v1alpha2.ApiServerSourceList, error) {
 	sourceList, err := c.client.List(metav1.ListOptions{})
 	if err != nil {
-		return nil, err
+		return nil, knerrors.GetError(err)
 	}
 
 	return updateAPIServerSourceListGVK(sourceList)

pkg/sources/v1alpha2/client.go

@@ -15,6 +15,10 @@
 package v1alpha2
 
 import (
+	"strings"
+
+	"k8s.io/apimachinery/pkg/runtime/schema"
+	sourcesv1alpha2 "knative.dev/eventing/pkg/apis/sources/v1alpha2"
 	clientv1alpha2 "knative.dev/eventing/pkg/client/clientset/versioned/typed/sources/v1alpha2"
 )
 
@@ -61,3 +65,13 @@ func (c *sourcesClient) SinkBindingClient() KnSinkBindingClient {
 func (c *sourcesClient) APIServerSourcesClient() KnAPIServerSourcesClient {
 	return newKnAPIServerSourcesClient(c.client.ApiServerSources(c.namespace), c.namespace)
 }
+
+// BuiltInSourcesGVKs returns the GVKs for built in sources
+func BuiltInSourcesGVKs() []schema.GroupVersionKind {
+	return []schema.GroupVersionKind{
+		sourcesv1alpha2.SchemeGroupVersion.WithKind("ApiServerSource"),
+		sourcesv1alpha2.SchemeGroupVersion.WithKind("ContainerSource"),
+		sourcesv1alpha2.SchemeGroupVersion.WithKind("PingSource"),
+		sourcesv1alpha2.SchemeGroupVersion.WithKind("SinkBinding"),
+	}
+}