Plugin model; --pattern=addon flag that generates an addon operator

We implement the initial plugin model, starting with an in-process
implementation that can support out-of-process later.  As plugins do
not yet form part of the stable interface for kubebuilder, we only
enable them when the KUBEBUILDER_ENABLE_PLUGINS env var is set.

We implement an initial plugin for addons: `--pattern=addon` creates a
controller & resource that follow the style of
https://github.com/kubernetes-sigs/kubebuilder-declarative-pattern

This style of declarative addon operators is being investigated in the
cluster-addons subject, with code at
https://github.com/kubernetes-sigs/addon-operators

Author: justinsb

cmd/api.go

@@ -22,13 +22,15 @@ import (
 	"log"
 	"os"
 	"os/exec"
+	"strings"
 
 	"github.com/spf13/cobra"
 	flag "github.com/spf13/pflag"
 
 	"sigs.k8s.io/kubebuilder/cmd/util"
 	"sigs.k8s.io/kubebuilder/pkg/scaffold"
 	"sigs.k8s.io/kubebuilder/pkg/scaffold/v1/resource"
+	"sigs.k8s.io/kubebuilder/plugins/addon"
 )
 
 type apiOptions struct {
@@ -37,6 +39,9 @@ type apiOptions struct {
 
 	// runMake indicates whether to run make or not after scaffolding APIs
 	runMake bool
+
+	// pattern indicates that we should use a plugin to build according to a pattern
+	pattern string
 }
 
 func (o *apiOptions) bindCmdFlags(cmd *cobra.Command) {
@@ -48,6 +53,10 @@ func (o *apiOptions) bindCmdFlags(cmd *cobra.Command) {
 	cmd.Flags().BoolVar(&o.apiScaffolder.DoController, "controller", true,
 		"if set, generate the controller without prompting the user")
 	o.controllerFlag = cmd.Flag("controller")
+	if os.Getenv("KUBEBUILDER_ENABLE_PLUGINS") != "" {
+		cmd.Flags().StringVar(&o.pattern, "pattern", "",
+			"generates an API following an extension pattern (addon)")
+	}
 	o.apiScaffolder.Resource = resourceForFlags(cmd.Flags())
 }
 
@@ -67,6 +76,17 @@ func resourceForFlags(f *flag.FlagSet) *resource.Resource {
 func (o *apiOptions) runAddAPI() {
 	dieIfNoProject()
 
+	switch strings.ToLower(o.pattern) {
+	case "":
+		// Default pattern
+
+	case "addon":
+		o.apiScaffolder.Plugins = append(o.apiScaffolder.Plugins, &addon.Plugin{})
+
+	default:
+		log.Fatalf("unknown pattern %q", o.pattern)
+	}
+
 	reader := bufio.NewReader(os.Stdin)
 	if !o.resourceFlag.Changed {
 		fmt.Println("Create Resource [y/n]")

cmd/vendor_update.go

@@ -20,6 +20,7 @@ import (
 	"log"
 
 	"github.com/spf13/cobra"
+	"sigs.k8s.io/kubebuilder/pkg/model"
 	"sigs.k8s.io/kubebuilder/pkg/scaffold"
 	"sigs.k8s.io/kubebuilder/pkg/scaffold/input"
 	"sigs.k8s.io/kubebuilder/pkg/scaffold/project"
@@ -35,7 +36,9 @@ kubebuilder update vendor
 `,
 		Run: func(cmd *cobra.Command, args []string) {
 			dieIfNoProject()
-			err := (&scaffold.Scaffold{}).Execute(input.Options{},
+			err := (&scaffold.Scaffold{}).Execute(
+				&model.Universe{},
+				input.Options{},
 				&project.GopkgToml{})
 			if err != nil {
 				log.Fatalf("error updating vendor dependecies %v", err)

cmd/webhook_v1.go

@@ -27,6 +27,7 @@ import (
 	"github.com/spf13/cobra"
 	flag "github.com/spf13/pflag"
 
+	"sigs.k8s.io/kubebuilder/pkg/model"
 	"sigs.k8s.io/kubebuilder/pkg/scaffold"
 	"sigs.k8s.io/kubebuilder/pkg/scaffold/input"
 	"sigs.k8s.io/kubebuilder/pkg/scaffold/project"
@@ -68,7 +69,9 @@ This command is only available for v1 scaffolding project.
 				o.res.Resource = flect.Pluralize(strings.ToLower(o.res.Kind))
 			}
 
-			err = (&scaffold.Scaffold{}).Execute(input.Options{},
+			err = (&scaffold.Scaffold{}).Execute(
+				&model.Universe{},
+				input.Options{},
 				&manager.Webhook{},
 				&webhook.AdmissionHandler{Resource: o.res, Config: webhook.Config{Server: o.server, Type: o.webhookType, Operations: o.operations}},
 				&webhook.AdmissionWebhookBuilder{Resource: o.res, Config: webhook.Config{Server: o.server, Type: o.webhookType, Operations: o.operations}},

cmd/webhook_v2.go

@@ -26,6 +26,7 @@ import (
 	"github.com/gobuffalo/flect"
 	"github.com/spf13/cobra"
 
+	"sigs.k8s.io/kubebuilder/pkg/model"
 	"sigs.k8s.io/kubebuilder/pkg/scaffold"
 	"sigs.k8s.io/kubebuilder/pkg/scaffold/input"
 	"sigs.k8s.io/kubebuilder/pkg/scaffold/project"
@@ -82,6 +83,7 @@ You need to implement the conversion.Hub and conversion.Convertible interfaces f
 				Validating: o.validation,
 			}
 			err = (&scaffold.Scaffold{}).Execute(
+				&model.Universe{},
 				input.Options{},
 				webhookScaffolder,
 			)

pkg/model/types.go

@@ -0,0 +1,55 @@
+package model
+
+import (
+	"sigs.k8s.io/kubebuilder/pkg/scaffold/input"
+)
+
+// Universe describes the entire state of file generation
+type Universe struct {
+	Boilerplate string `json:"boilerplate,omitempty"`
+
+	Resource *Resource `json:"resource,omitempty"`
+
+	Files []*File `json:"files,omitempty"`
+}
+
+// Resource describes the resource currently being generated
+// TODO: Just use the resource type?
+type Resource struct {
+	// Namespaced is true if the resource is namespaced
+	Namespaced bool `json:"namespaces,omitempty"`
+
+	// Group is the API Group.  Does not contain the domain.
+	Group string `json:"group,omitempty"`
+
+	// Version is the API version - e.g. v1beta1
+	Version string `json:"version,omitempty"`
+
+	// Kind is the API Kind.
+	Kind string `json:"kind,omitempty"`
+
+	// Plural is the plural lowercase of Kind.
+	Plural string `json:"plural,omitempty"`
+
+	// Resource is the API Resource.
+	Resource string `json:"resource,omitempty"`
+
+	// ResourcePackage is the go package of the Resource
+	GoPackage string `json:"goPackage,omitempty"`
+
+	// GroupDomain is the Group + "." + Domain for the Resource
+	GroupDomain string `json:"groupDomain,omitempty"`
+}
+
+// File describes a file that will be written
+type File struct {
+	// Path is the file to write
+	Path string `json:"path,omitempty"`
+
+	// Contents is the generated output
+	Contents string `json:"contents,omitempty"`
+
+	// TODO: Move input.IfExistsAction into model
+	// IfExistsAction determines what to do if the file exists
+	IfExistsAction input.IfExistsAction `json:"ifExistsAction,omitempty"`
+}

pkg/scaffold/api.go

@@ -21,8 +21,11 @@ import (
 	"path/filepath"
 	"strings"
 
+	"github.com/gobuffalo/flect"
+	"sigs.k8s.io/kubebuilder/pkg/model"
 	"sigs.k8s.io/kubebuilder/pkg/scaffold/input"
 	"sigs.k8s.io/kubebuilder/pkg/scaffold/project"
+	"sigs.k8s.io/kubebuilder/pkg/scaffold/util"
 	"sigs.k8s.io/kubebuilder/pkg/scaffold/v1/controller"
 	resourcev1 "sigs.k8s.io/kubebuilder/pkg/scaffold/v1/resource"
 	resourcev2 "sigs.k8s.io/kubebuilder/pkg/scaffold/v2"
@@ -34,6 +37,9 @@ import (
 type API struct {
 	scaffold *Scaffold
 
+	// Plugins is the list of plugins we should allow to transform our generated scaffolding
+	Plugins []Plugin
+
 	Resource *resourcev1.Resource
 
 	project *input.ProjectFile
@@ -60,6 +66,7 @@ func (api *API) Validate() error {
 	if api.Resource.Kind == "" {
 		return fmt.Errorf("missing kind information for resource")
 	}
+
 	return nil
 }
 
@@ -89,6 +96,23 @@ func (api *API) Scaffold() error {
 	}
 }
 
+func (api *API) buildUniverse() *model.Universe {
+	resource := &model.Resource{
+		Namespaced: api.Resource.Namespaced,
+		Group:      api.Resource.Group,
+		Version:    api.Resource.Version,
+		Kind:       api.Resource.Kind,
+		Resource:   api.Resource.Resource,
+		Plural:     flect.Pluralize(strings.ToLower(api.Resource.Kind)),
+	}
+
+	resource.GoPackage, resource.GroupDomain = util.GetResourceInfo(api.Resource, api.project.Repo, api.project.Domain)
+
+	return &model.Universe{
+		Resource: resource,
+	}
+}
+
 func (api *API) scaffoldV1() error {
 	r := api.Resource
 
@@ -98,7 +122,7 @@ func (api *API) scaffoldV1() error {
 		fmt.Println(filepath.Join("pkg", "apis", r.Group, r.Version,
 			fmt.Sprintf("%s_types_test.go", strings.ToLower(r.Kind))))
 
-		err := (&Scaffold{}).Execute(input.Options{},
+		err := (&Scaffold{}).Execute(api.buildUniverse(), input.Options{},
 			&resourcev1.Register{Resource: r},
 			&resourcev1.Types{Resource: r},
 			&resourcev1.VersionSuiteTest{Resource: r},
@@ -125,7 +149,7 @@ func (api *API) scaffoldV1() error {
 		fmt.Println(filepath.Join("pkg", "controller", strings.ToLower(r.Kind),
 			fmt.Sprintf("%s_controller_test.go", strings.ToLower(r.Kind))))
 
-		err := (&Scaffold{}).Execute(input.Options{},
+		err := (&Scaffold{}).Execute(api.buildUniverse(), input.Options{},
 			&controller.Controller{Resource: r},
 			&controller.AddController{Resource: r},
 			&controller.Test{Resource: r},
@@ -150,8 +174,7 @@ func (api *API) scaffoldV2() error {
 		fmt.Println(filepath.Join("api", r.Version,
 			fmt.Sprintf("%s_types.go", strings.ToLower(r.Kind))))
 
-		err := (&Scaffold{}).Execute(
-			input.Options{},
+		files := []input.File{
 			&resourcev2.Types{
 				Input: input.Input{
 					Path: filepath.Join("api", r.Version, fmt.Sprintf("%s_types.go", strings.ToLower(r.Kind))),
@@ -161,13 +184,18 @@ func (api *API) scaffoldV2() error {
 			&resourcev2.CRDSample{Resource: r},
 			&crdv2.EnableWebhookPatch{Resource: r},
 			&crdv2.EnableCAInjectionPatch{Resource: r},
-		)
-		if err != nil {
+		}
+
+		scaffold := &Scaffold{
+			Plugins: api.Plugins,
+		}
+
+		if err := scaffold.Execute(api.buildUniverse(), input.Options{}, files...); err != nil {
 			return fmt.Errorf("error scaffolding APIs: %v", err)
 		}
 
 		crdKustomization := &crdv2.Kustomization{Resource: r}
-		err = (&Scaffold{}).Execute(
+		err := (&Scaffold{}).Execute(api.buildUniverse(),
 			input.Options{},
 			crdKustomization,
 			&crdv2.KustomizeConfig{},
@@ -203,6 +231,7 @@ func (api *API) scaffoldV2() error {
 		ctrlScaffolder := &resourcev2.Controller{Resource: r}
 		testsuiteScaffolder := &resourcev2.ControllerSuiteTest{Resource: r}
 		err := (&Scaffold{}).Execute(
+			api.buildUniverse(),
 			input.Options{},
 			testsuiteScaffolder,
 			ctrlScaffolder,

pkg/scaffold/project.go

@@ -24,6 +24,7 @@ import (
 	"strings"
 
 	"sigs.k8s.io/kubebuilder/cmd/util"
+	"sigs.k8s.io/kubebuilder/pkg/model"
 	"sigs.k8s.io/kubebuilder/pkg/scaffold/input"
 	"sigs.k8s.io/kubebuilder/pkg/scaffold/project"
 	scaffoldv1 "sigs.k8s.io/kubebuilder/pkg/scaffold/v1"
@@ -77,6 +78,10 @@ func (p *V1Project) EnsureDependencies() (bool, error) {
 	return true, c.Run()
 }
 
+func (p *V1Project) buildUniverse() *model.Universe {
+	return &model.Universe{}
+}
+
 func (p *V1Project) Scaffold() error {
 	p.Project.Version = project.Version1
 
@@ -96,6 +101,7 @@ func (p *V1Project) Scaffold() error {
 	}
 
 	err = s.Execute(
+		p.buildUniverse(),
 		input.Options{ProjectPath: projectInput.Path, BoilerplatePath: bpInput.Path},
 		&p.Project,
 		&p.Boilerplate,
@@ -109,6 +115,7 @@ func (p *V1Project) Scaffold() error {
 
 	s = &Scaffold{}
 	return s.Execute(
+		p.buildUniverse(),
 		input.Options{ProjectPath: projectInput.Path, BoilerplatePath: bpInput.Path},
 		&project.GitIgnore{},
 		&project.KustomizeRBAC{},
@@ -147,6 +154,10 @@ func (p *V2Project) EnsureDependencies() (bool, error) {
 	return true, c.Run()
 }
 
+func (p *V2Project) buildUniverse() *model.Universe {
+	return &model.Universe{}
+}
+
 func (p *V2Project) Scaffold() error {
 	p.Project.Version = project.Version2
 
@@ -166,6 +177,7 @@ func (p *V2Project) Scaffold() error {
 	}
 
 	err = s.Execute(
+		p.buildUniverse(),
 		input.Options{ProjectPath: projectInput.Path, BoilerplatePath: bpInput.Path},
 		&p.Project,
 		&p.Boilerplate,
@@ -179,6 +191,7 @@ func (p *V2Project) Scaffold() error {
 
 	s = &Scaffold{}
 	return s.Execute(
+		p.buildUniverse(),
 		input.Options{ProjectPath: projectInput.Path, BoilerplatePath: bpInput.Path},
 		&project.GitIgnore{},
 		&metricsauthv2.KustomizePrometheusMetricsPatch{},