Add generation for getting objects from requests

In order to validate objects, the new and old objects, if they exist,
should be pull from the webhook request. This process is identical for
all objects except that the return types would be different. This is a
candidate for code generation, and this generation is added.

.gitignore

@@ -5,4 +5,5 @@
 /dist
 *.swp
 .idea
+.vscode
 /webhook

.golangci.json

@@ -11,6 +11,9 @@
 		]
 	},
 	"run": {
+		"skip-dirs": [
+			"pkg/generated"
+		],
 		"skip-files": [
 			"/zz_generated_"
 		],

go.mod

@@ -38,6 +38,7 @@ require (
 	github.com/rancher/rancher/pkg/apis v0.0.0-20210628154046-7a2fc74f9598
 	github.com/rancher/wrangler v0.8.3
 	github.com/sirupsen/logrus v1.8.1
+	golang.org/x/tools v0.1.0
 	k8s.io/api v0.21.0
 	k8s.io/apiextensions-apiserver v0.21.0
 	k8s.io/apimachinery v0.21.0

main.go

@@ -1,5 +1,5 @@
 //go:generate go run pkg/codegen/cleanup/main.go
-//go:generate go run pkg/codegen/main.go
+//go:generate go run pkg/codegen/main.go pkg/codegen/template.go
 package main
 
 import (

pkg/codegen/main.go

@@ -1,13 +1,25 @@
 package main
 
 import (
+	"bytes"
+	"fmt"
 	"os"
+	"path"
+	"reflect"
+	"strings"
+	"text/template"
 
 	v3 "github.com/rancher/rancher/pkg/apis/management.cattle.io/v3"
+	v1 "github.com/rancher/rancher/pkg/apis/provisioning.cattle.io/v1"
 	controllergen "github.com/rancher/wrangler/pkg/controller-gen"
 	"github.com/rancher/wrangler/pkg/controller-gen/args"
+	"golang.org/x/tools/imports"
 )
 
+type typeInfo struct {
+	Name, Type, Package string
+}
+
 func main() {
 	os.Unsetenv("GOPATH")
 	controllergen.Run(args.Options{
@@ -23,4 +35,88 @@ func main() {
 			},
 		},
 	})
+
+	// Generate the <TYPE>FromRequest and <TYPE>OldAndNewFromRequest functions to get the new and old objects from the webhook request.
+	if err := generateObjectsFromRequest("pkg/generated/objects", map[string]args.Group{
+		"management.cattle.io": {
+			Types: []interface{}{
+				&v3.Cluster{},
+				&v3.ClusterRoleTemplateBinding{},
+				&v3.FleetWorkspace{},
+				&v3.GlobalRole{},
+				&v3.GlobalRoleBinding{},
+				&v3.RoleTemplate{},
+				&v3.ProjectRoleTemplateBinding{},
+			},
+		},
+		"provisioning.cattle.io": {
+			Types: []interface{}{
+				&v1.Cluster{},
+			},
+		}}); err != nil {
+		fmt.Printf("ERROR: %v\n", err)
+	}
+}
+
+func generateObjectsFromRequest(outputDir string, groups map[string]args.Group) error {
+	temp := template.Must(template.New("objectsFromRequest").Funcs(template.FuncMap{
+		"replace": strings.ReplaceAll,
+	}).Parse(objectsFromRequestTemplate))
+
+	for groupName, group := range groups {
+		var packageName string
+		types := make([]typeInfo, 0, len(group.Types))
+
+		for _, t := range group.Types {
+			rt := reflect.TypeOf(t)
+			ti := typeInfo{
+				Type: rt.String(),
+			}
+			if rt.Kind() == reflect.Ptr {
+				// PkgPath returns an empty string for pointers
+				// Elem returns a Type associated to the dereferenced type.
+				rt = rt.Elem()
+			}
+			ti.Package = rt.PkgPath()
+			ti.Name = rt.Name()
+			packageName = path.Base(ti.Package)
+			types = append(types, ti)
+		}
+
+		groupDir := path.Join(outputDir, groupName, packageName)
+		if err := os.MkdirAll(groupDir, 0755); err != nil {
+			return err
+		}
+
+		data := map[string]interface{}{
+			"types":   types,
+			"package": packageName,
+		}
+
+		var content bytes.Buffer
+		if err := temp.Execute(&content, data); err != nil {
+			return err
+		}
+
+		if err := gofmtAndWriteToFile(path.Join(groupDir, "objects.go"), content.Bytes()); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
+func gofmtAndWriteToFile(path string, content []byte) error {
+	formatted, err := imports.Process(path, content, &imports.Options{FormatOnly: true, Comments: true})
+	if err != nil {
+		return err
+	}
+	f, err := os.Create(path)
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+
+	_, err = f.Write(formatted)
+	return err
 }

pkg/codegen/template.go

@@ -0,0 +1,61 @@
+package main
+
+const objectsFromRequestTemplate = `
+package {{ .package }}
+
+import (
+	{{ range .types }}
+	"{{ .Package }}"{{ end }}
+	"github.com/rancher/wrangler/pkg/webhook"
+	admissionv1 "k8s.io/api/admission/v1"
+	"k8s.io/apimachinery/pkg/runtime"
+)
+{{ range .types }}
+
+// {{ .Name }}OldAndNewFromRequest gets the old and new {{ .Name }} objects, respectively, from the webhook request.
+// If the request is a Delete operation, then the new object is the zero value for {{ .Name }}.
+// Similarly, if the request is a Create operation, then the old object is the zero value for {{ .Name }}.
+func {{ .Name }}OldAndNewFromRequest(request *webhook.Request) ({{ .Type }}, {{ .Type }}, error) {
+	var object runtime.Object
+	var err error
+	if request.Operation != admissionv1.Delete {
+		object, err = request.DecodeObject()
+		if err != nil {
+			return nil, nil, err
+		}
+	} else {
+		object = {{ replace .Type "*" "&" }}{}
+	}
+
+	if request.Operation == admissionv1.Create {
+		return {{ replace .Type "*" "&" }}{}, object.({{ .Type }}), nil
+	}
+
+	oldObject, err := request.DecodeOldObject()
+	if err != nil {
+		return nil, nil, err
+	}
+
+	return oldObject.({{ .Type }}), object.({{ .Type }}), nil
+}
+
+// {{ .Name }}FromRequest returns a {{ .Name }} object from the webhook request.
+// If the operation is a Delete operation, then the old object is returned.
+// Otherwise, the new object is returned.
+func {{ .Name }}FromRequest(request *webhook.Request) ({{ .Type }}, error) {
+	var object runtime.Object
+	var err error
+	if request.Operation == admissionv1.Delete {
+		object, err = request.DecodeOldObject()
+	} else {
+		object, err = request.DecodeObject()
+	}
+
+	if err != nil {
+		return nil, err
+	}
+
+	return object.({{ .Type }}), nil
+}
+{{ end }}
+`