✨ Provide third-party devs the option to provide their own alpha subcommands

pkg/cli/alpha.go

@@ -17,19 +17,24 @@ limitations under the License.
 package cli
 
 import (
+	"fmt"
 	"strings"
 
 	"github.com/spf13/cobra"
 	configgen "sigs.k8s.io/kubebuilder/v3/pkg/cli/alpha/config-gen"
 )
 
+const (
+	alphaCommand = "alpha"
+)
+
 var alphaCommands = []*cobra.Command{
 	configgen.NewCommand(),
 }
 
 func (c *CLI) newAlphaCmd() *cobra.Command {
 	alpha := &cobra.Command{
-		Use:        "alpha",
+		Use:        alphaCommand,
 		SuggestFor: []string{"experimental"},
 		Short:      "Alpha kubebuilder subcommands",
 		Long: strings.TrimSpace(`
@@ -46,7 +51,31 @@ Alpha kubebuilder commands are for unstable features.
 }
 
 func (c *CLI) addAlphaCmd() {
-	if len(alphaCommands) > 0 {
+	if (len(alphaCommands) + len(c.extraAlphaCommands)) > 0 {
 		c.cmd.AddCommand(c.newAlphaCmd())
 	}
 }
+
+func (c *CLI) addExtraAlphaCommands() error {
+	// Search for the alpha subcommand
+	var alpha *cobra.Command
+	for _, subCmd := range c.cmd.Commands() {
+		if subCmd.Name() == alphaCommand {
+			alpha = subCmd
+			break
+		}
+	}
+	if alpha == nil {
+		return fmt.Errorf("no %q command found", alphaCommand)
+	}
+
+	for _, cmd := range c.extraAlphaCommands {
+		for _, subCmd := range alpha.Commands() {
+			if cmd.Name() == subCmd.Name() {
+				return fmt.Errorf("command %q already exists", fmt.Sprintf("%s %s", alphaCommand, cmd.Name()))
+			}
+		}
+		c.cmd.AddCommand(cmd)
+	}
+	return nil
+}

pkg/cli/cli.go

@@ -75,6 +75,8 @@ type CLI struct { //nolint:maligned
 	plugins map[string]plugin.Plugin
 	// Commands injected by options.
 	extraCommands []*cobra.Command
+	// Alpha commands injected by options.
+	extraAlphaCommands []*cobra.Command
 	// Whether to add a completion command to the CLI.
 	completionCommand bool
 
@@ -121,6 +123,11 @@ func New(options ...Option) (*CLI, error) {
 		return nil, err
 	}
 
+	// Add extra alpha commands injected by options.
+	if err := c.addExtraAlphaCommands(); err != nil {
+		return nil, err
+	}
+
 	// Write deprecation notices after all commands have been constructed.
 	c.printDeprecationWarnings()
 

pkg/cli/options.go

@@ -112,6 +112,18 @@ func WithExtraCommands(cmds ...*cobra.Command) Option {
 	}
 }
 
+// WithExtraAlphaCommands is an Option that adds extra alpha subcommands to the CLI.
+//
+// Adding extra alpha commands that duplicate existing commands results in an error.
+func WithExtraAlphaCommands(cmds ...*cobra.Command) Option {
+	return func(c *CLI) error {
+		// We don't know the commands defined by the CLI yet so we are not checking if the extra alpha commands
+		// conflict with a pre-existing one yet. We do this after creating the base commands.
+		c.extraAlphaCommands = append(c.extraAlphaCommands, cmds...)
+		return nil
+	}
+}
+
 // WithCompletion is an Option that adds the completion subcommand.
 func WithCompletion() Option {
 	return func(c *CLI) error {

pkg/cli/options_test.go

@@ -221,6 +221,21 @@ var _ = Describe("CLI options", func() {
 		})
 	})
 
+	Context("WithExtraAlphaCommands", func() {
+		It("should return a valid CLI with extra alpha commands", func() {
+			commandTest := &cobra.Command{
+				Use: "example",
+			}
+			c, err = newCLI(WithExtraAlphaCommands(commandTest))
+			Expect(err).NotTo(HaveOccurred())
+			Expect(c).NotTo(BeNil())
+			Expect(c.extraAlphaCommands).NotTo(BeNil())
+			Expect(len(c.extraAlphaCommands)).To(Equal(1))
+			Expect(c.extraAlphaCommands[0]).NotTo(BeNil())
+			Expect(c.extraAlphaCommands[0].Use).To(Equal(commandTest.Use))
+		})
+	})
+
 	Context("WithCompletion", func() {
 		It("should not add the completion command by default", func() {
 			c, err = newCLI()