Support specifying the type of channel to create using --type

 Default is to use messaging layer configuration for channels.

docs/cmd/kn_channel_create.md

@@ -14,15 +14,22 @@ kn channel create NAME
 
 ```
 
-  # Create a channel 'pipe' in namespace 'flow'
-  kn channel create pipe -n flow
+  # Create a channel 'pipe' with default setting for channel configuration
+  kn channel create pipe
+
+  # Create a channel 'imc1' of type InMemoryChannel
+  kn channel create imc1 --type messaging.knative.dev:v1beta1:InMemoryChannel
+
+  # Create a channel 'k1' of type KafkaChannel
+  kn channel create k1 --type messaging.knative.dev:v1alpha1:KafkaChannel
 ```
 
 ### Options
 
 ```
   -h, --help               help for create
   -n, --namespace string   Specify the namespace to operate in.
+      --type string        Type of the channel to create in the format 'Group:Version:Kind'. For example: '--type messaging.knative.dev:v1alpha1:KafkaChannel'. Default is to use messaging layer setting for default channel configuration.
 ```
 
 ### Options inherited from parent commands

pkg/kn/commands/channel/create.go

@@ -17,8 +17,10 @@ package channel
 import (
 	"errors"
 	"fmt"
+	"strings"
 
 	"github.com/spf13/cobra"
+	"k8s.io/apimachinery/pkg/runtime/schema"
 
 	knerrors "knative.dev/client/pkg/errors"
 	"knative.dev/client/pkg/kn/commands"
@@ -31,8 +33,15 @@ func NewChannelCreateCommand(p *commands.KnParams) *cobra.Command {
 		Use:   "create NAME",
 		Short: "Create an event channel",
 		Example: `
-  # Create a channel 'pipe' in namespace 'flow'
-  kn channel create pipe -n flow`,
+  # Create a channel 'pipe' with default setting for channel configuration
+  kn channel create pipe
+
+  # Create a channel 'imc1' of type InMemoryChannel
+  kn channel create imc1 --type messaging.knative.dev:v1beta1:InMemoryChannel
+
+  # Create a channel 'k1' of type KafkaChannel
+  kn channel create k1 --type messaging.knative.dev:v1alpha1:KafkaChannel`,
+
 		RunE: func(cmd *cobra.Command, args []string) (err error) {
 			if len(args) != 1 {
 				return errors.New("'kn channel create' requires the channel name given as single argument")
@@ -49,7 +58,17 @@ func NewChannelCreateCommand(p *commands.KnParams) *cobra.Command {
 				return err
 			}
 
-			err = client.CreateChannel(knmessagingv1beta1.NewChannelBuilder(name).Build())
+			cb := knmessagingv1beta1.NewChannelBuilder(name)
+
+			if cmd.Flag("type").Changed {
+				gvk, err := processType(cmd.Flag("type").Value.String())
+				if err != nil {
+					return err
+				}
+				cb.Type(*gvk)
+			}
+
+			err = client.CreateChannel(cb.Build())
 			if err != nil {
 				return knerrors.GetError(err)
 			}
@@ -59,5 +78,14 @@ func NewChannelCreateCommand(p *commands.KnParams) *cobra.Command {
 		},
 	}
 	commands.AddNamespaceFlags(cmd.Flags(), false)
+	cmd.Flags().String("type", "", "Type of the channel to create in the format 'Group:Version:Kind'. For example: '--type messaging.knative.dev:v1alpha1:KafkaChannel'. Default is to use messaging layer setting for default channel configuration.")
 	return cmd
 }
+
+func processType(t string) (*schema.GroupVersionKind, error) {
+	parts := strings.Split(t, ":")
+	if len(parts) != 3 || parts[0] == "" || parts[1] == "" || parts[2] == "" {
+		return nil, errors.New(fmt.Sprintf("Error: incorrect value '%s' for '--type', must be in the format 'Group:Version:Kind'", t))
+	}
+	return &schema.GroupVersionKind{Group: parts[0], Version: parts[1], Kind: parts[2]}, nil
+}

pkg/messaging/v1beta1/messaging_client.go

@@ -16,6 +16,7 @@ package v1beta1
 
 import (
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+	"k8s.io/apimachinery/pkg/runtime/schema"
 	"knative.dev/eventing/pkg/apis/messaging/v1beta1"
 	clientv1beta1 "knative.dev/eventing/pkg/client/clientset/versioned/typed/messaging/v1beta1"
 
@@ -136,6 +137,15 @@ func NewChannelBuilder(name string) *ChannelBuilder {
 	}}
 }
 
+// Type sets the type of the channel to create
+func (c *ChannelBuilder) Type(gvk schema.GroupVersionKind) *v1beta1.Channel {
+	spec := &v1beta1.ChannelTemplateSpec{}
+	spec.Kind = gvk.Kind
+	spec.APIVersion = gvk.GroupVersion().String()
+	c.channel.Spec.ChannelTemplate = spec
+	return c.channel
+}
+
 // Build returns the Channel object from the builder
 func (c *ChannelBuilder) Build() *v1beta1.Channel {
 	return c.channel