implement passing flags to external plugins

Signed-off-by: Bryce Palmer <bpalmer@redhat.com>

pkg/cli/options.go

@@ -155,8 +155,18 @@ func WithCompletion() Option {
 
 // parseExternalPluginArgs returns the program arguments.
 func parseExternalPluginArgs() (args []string) {
-	args = make([]string, len(os.Args)-1)
-	copy(args, os.Args[1:])
+	// Loop through os.Args and only get flags and their values that should be passed to the plugins
+	// this also removes the --plugins flag and its values from the list passed to the external plugin
+	for i := range os.Args {
+		if strings.Contains(os.Args[i], "--") && !strings.Contains(os.Args[i], "--plugins") {
+			args = append(args, os.Args[i])
+
+			// Don't go out of bounds and don't append the next value if it is a flag
+			if i+1 < len(os.Args) && !strings.Contains(os.Args[i+1], "--") {
+				args = append(args, os.Args[i+1])
+			}
+		}
+	}
 
 	return args
 }

pkg/cli/options_test.go

@@ -283,6 +283,43 @@ var _ = Describe("Discover external plugins", func() {
 
 		})
 	})
+
+	Context("parsing flags for external plugins", func() {
+		It("should only parse flags excluding the `--plugins` flag", func() {
+			// change the os.Args for this test and set them back after
+			oldArgs := os.Args
+			defer func() { os.Args = oldArgs }()
+			os.Args = []string{
+				"kubebuilder",
+				"init",
+				"--plugins",
+				"myexternalplugin/v1",
+				"--domain",
+				"example.com",
+				"--binary-flag",
+				"--license",
+				"apache2",
+				"--another-binary",
+			}
+
+			args := parseExternalPluginArgs()
+			Expect(args).Should(ContainElements(
+				"--domain",
+				"example.com",
+				"--binary-flag",
+				"--license",
+				"apache2",
+				"--another-binary",
+			))
+
+			Expect(args).ShouldNot(ContainElements(
+				"kubebuilder",
+				"init",
+				"--plugins",
+				"myexternalplugin/v1",
+			))
+		})
+	})
 })
 
 var _ = Describe("CLI options", func() {

pkg/plugin/external/types.go

@@ -57,4 +57,29 @@ type PluginResponse struct {
 
 	// ErrorMsgs contains the specific error messages of the plugin failures.
 	ErrorMsgs []string `json:"errorMsgs,omitempty"`
+
+	// Flags contains the plugin specific flags that the plugin returns to Kubebuilder when it receives
+	// a request for a list of supported flags from Kubebuilder
+	Flags []Flag `json:"flags,omitempty"`
+}
+
+// Flag is meant to represent a CLI flag that is used by Kubebuilder to define flags that are parsed
+// for use with an external plugin
+type Flag struct {
+	// Name is the name that should be used when creating the flag.
+	// i.e a name of "domain" would become the CLI flag "--domain"
+	Name string
+
+	// Type is the type of flag that should be created. The types that
+	// Kubebuilder supports are: string, bool, int, and float.
+	// any value other than the supported will be defaulted to be a string
+	Type string
+
+	// Default is the default value that should be used for a flag.
+	// Kubebuilder will attempt to convert this value to the defined
+	// type for this flag.
+	Default string
+
+	// Usage is a description of the flag and when/why/what it is used for.
+	Usage string
 }

pkg/plugins/external/api.go

@@ -17,6 +17,8 @@ limitations under the License.
 package external
 
 import (
+	"github.com/spf13/pflag"
+
 	"sigs.k8s.io/kubebuilder/v3/pkg/machinery"
 	"sigs.k8s.io/kubebuilder/v3/pkg/model/resource"
 	"sigs.k8s.io/kubebuilder/v3/pkg/plugin"
@@ -39,6 +41,10 @@ func (p *createAPISubcommand) InjectResource(*resource.Resource) error {
 	return nil
 }
 
+func (p *createAPISubcommand) BindFlags(fs *pflag.FlagSet) {
+	bindExternalPluginFlags(fs, "api", p.Path, p.Args)
+}
+
 func (p *createAPISubcommand) Scaffold(fs machinery.Filesystem) error {
 	req := external.PluginRequest{
 		APIVersion: defaultAPIVersion,

pkg/plugins/external/edit.go

@@ -17,6 +17,8 @@ limitations under the License.
 package external
 
 import (
+	"github.com/spf13/pflag"
+
 	"sigs.k8s.io/kubebuilder/v3/pkg/machinery"
 	"sigs.k8s.io/kubebuilder/v3/pkg/plugin"
 	"sigs.k8s.io/kubebuilder/v3/pkg/plugin/external"
@@ -29,6 +31,10 @@ type editSubcommand struct {
 	Args []string
 }
 
+func (p *editSubcommand) BindFlags(fs *pflag.FlagSet) {
+	bindExternalPluginFlags(fs, "edit", p.Path, p.Args)
+}
+
 func (p *editSubcommand) Scaffold(fs machinery.Filesystem) error {
 	req := external.PluginRequest{
 		APIVersion: defaultAPIVersion,