code-generator: allow to customize generated verbs and add custom verb

staging/src/k8s.io/code-generator/cmd/client-gen/generators/fake/generator_fake_for_type.go

@@ -19,6 +19,7 @@ package fake
 import (
 	"io"
 	"path/filepath"
+	"strings"
 
 	"k8s.io/gengo/generator"
 	"k8s.io/gengo/namer"
@@ -108,6 +109,9 @@ func (g *genFakeForType) GenerateType(c *generator.Context, t *types.Type, w io.
 	const pkgClientGoTesting = "k8s.io/client-go/testing"
 	m := map[string]interface{}{
 		"type":                 t,
+		"inputType":            t,
+		"resultType":           t,
+		"subresourcePath":      "",
 		"package":              pkg,
 		"Package":              namer.IC(pkg),
 		"namespaced":           !tags.NonNamespaced,
@@ -139,7 +143,10 @@ func (g *genFakeForType) GenerateType(c *generator.Context, t *types.Type, w io.
 		"NewCreateAction":                c.Universe.Function(types.Name{Package: pkgClientGoTesting, Name: "NewCreateAction"}),
 		"NewRootWatchAction":             c.Universe.Function(types.Name{Package: pkgClientGoTesting, Name: "NewRootWatchAction"}),
 		"NewWatchAction":                 c.Universe.Function(types.Name{Package: pkgClientGoTesting, Name: "NewWatchAction"}),
+		"NewCreateSubresourceAction":     c.Universe.Function(types.Name{Package: pkgClientGoTesting, Name: "NewCreateSubresourceAction"}),
 		"NewUpdateSubresourceAction":     c.Universe.Function(types.Name{Package: pkgClientGoTesting, Name: "NewUpdateSubresourceAction"}),
+		"NewGetSubresourceAction":        c.Universe.Function(types.Name{Package: pkgClientGoTesting, Name: "NewGetSubresourceAction"}),
+		"NewListSubresourceAction":       c.Universe.Function(types.Name{Package: pkgClientGoTesting, Name: "NewListSubresourceAction"}),
 		"NewRootUpdateSubresourceAction": c.Universe.Function(types.Name{Package: pkgClientGoTesting, Name: "NewRootUpdateSubresourceAction"}),
 		"NewRootPatchAction":             c.Universe.Function(types.Name{Package: pkgClientGoTesting, Name: "NewRootPatchAction"}),
 		"NewPatchAction":                 c.Universe.Function(types.Name{Package: pkgClientGoTesting, Name: "NewPatchAction"}),
@@ -193,9 +200,88 @@ func (g *genFakeForType) GenerateType(c *generator.Context, t *types.Type, w io.
 		sw.Do(patchTemplate, m)
 	}
 
+	// generate extended client methods
+	for _, e := range tags.Extensions {
+		inputType := *t
+		resultType := *t
+		if len(e.InputTypeOverride) > 0 {
+			if name, pkg := e.Input(); len(pkg) > 0 {
+				newType := c.Universe.Type(types.Name{Package: pkg, Name: name})
+				inputType = *newType
+			} else {
+				inputType.Name.Name = e.InputTypeOverride
+			}
+		}
+		if len(e.ResultTypeOverride) > 0 {
+			if name, pkg := e.Result(); len(pkg) > 0 {
+				newType := c.Universe.Type(types.Name{Package: pkg, Name: name})
+				resultType = *newType
+			} else {
+				resultType.Name.Name = e.ResultTypeOverride
+			}
+		}
+		m["inputType"] = &inputType
+		m["resultType"] = &resultType
+		m["subresourcePath"] = e.SubResourcePath
+
+		if e.HasVerb("get") {
+			if e.IsSubresource() {
+				sw.Do(adjustTemplate(e.VerbName, e.VerbType, getSubresourceTemplate), m)
+			} else {
+				sw.Do(adjustTemplate(e.VerbName, e.VerbType, getTemplate), m)
+			}
+		}
+
+		if e.HasVerb("list") {
+			if e.IsSubresource() {
+				sw.Do(adjustTemplate(e.VerbName, e.VerbType, listSubresourceTemplate), m)
+			} else {
+				sw.Do(adjustTemplate(e.VerbName, e.VerbType, listTemplate), m)
+			}
+		}
+
+		// TODO: Figure out schemantic for watching a sub-resource.
+		if e.HasVerb("watch") {
+			sw.Do(adjustTemplate(e.VerbName, e.VerbType, watchTemplate), m)
+		}
+
+		if e.HasVerb("create") {
+			if e.IsSubresource() {
+				sw.Do(adjustTemplate(e.VerbName, e.VerbType, createSubresourceTemplate), m)
+			} else {
+				sw.Do(adjustTemplate(e.VerbName, e.VerbType, createTemplate), m)
+			}
+		}
+
+		if e.HasVerb("update") {
+			if e.IsSubresource() {
+				sw.Do(adjustTemplate(e.VerbName, e.VerbType, updateSubresourceTemplate), m)
+			} else {
+				sw.Do(adjustTemplate(e.VerbName, e.VerbType, updateTemplate), m)
+			}
+		}
+
+		// TODO: Figure out schemantic for deleting a sub-resource (what arguments
+		// are passed, does it need two names? etc.
+		if e.HasVerb("delete") {
+			sw.Do(adjustTemplate(e.VerbName, e.VerbType, deleteTemplate), m)
+		}
+
+		if e.HasVerb("patch") {
+			sw.Do(adjustTemplate(e.VerbName, e.VerbType, patchTemplate), m)
+		}
+	}
+
 	return sw.Error()
 }
 
+// adjustTemplate adjust the origin verb template using the expansion name.
+// TODO: Make the verbs in templates parametrized so the strings.Replace() is
+// not needed.
+func adjustTemplate(name, verbType, template string) string {
+	return strings.Replace(template, " "+strings.Title(verbType), " "+name, -1)
+}
+
 // template for the struct that implements the type's interface
 var structNamespaced = `
 // Fake$.type|publicPlural$ implements $.type|public$Interface
@@ -234,6 +320,19 @@ func (c *Fake$.type|publicPlural$) List(opts $.ListOptions|raw$) (result *$.type
 }
 `
 
+var listSubresourceTemplate = `
+// List takes label and field selectors, and returns the list of $.resultType|publicPlural$ that match those selectors.
+func (c *Fake$.type|publicPlural$) List($.type|private$Name string, opts $.ListOptions|raw$) (result *$.resultType|raw$List, err error) {
+	obj, err := c.Fake.
+		$if .namespaced$Invokes($.NewListSubresourceAction|raw$($.type|allLowercasePlural$Resource, $.type|private$Name, "$.subresourcePath$", $.type|allLowercasePlural$Kind, c.ns, opts), &$.resultType|raw$List{})
+		$else$Invokes($.NewRootListAction|raw$($.type|allLowercasePlural$Resource, $.type|allLowercasePlural$Kind, opts), &$.resultType|raw$List{})$end$
+	if obj == nil {
+		return nil, err
+	}
+	return obj.(*$.resultType|raw$List), err
+}
+`
+
 var listUsingOptionsTemplate = `
 // List takes label and field selectors, and returns the list of $.type|publicPlural$ that match those selectors.
 func (c *Fake$.type|publicPlural$) List(opts $.ListOptions|raw$) (result *$.type|raw$List, err error) {
@@ -259,15 +358,28 @@ func (c *Fake$.type|publicPlural$) List(opts $.ListOptions|raw$) (result *$.type
 `
 
 var getTemplate = `
-// Get takes name of the $.type|private$, and returns the corresponding $.type|private$ object, and an error if there is any.
+// Get takes name of the $.type|private$, and returns the corresponding $.resultType|private$ object, and an error if there is any.
-func (c *Fake$.type|publicPlural$) Get(name string, options $.GetOptions|raw$) (result *$.type|raw$, err error) {
+func (c *Fake$.type|publicPlural$) Get(name string, options $.GetOptions|raw$) (result *$.resultType|raw$, err error) {
 	obj, err := c.Fake.
-		$if .namespaced$Invokes($.NewGetAction|raw$($.type|allLowercasePlural$Resource, c.ns, name), &$.type|raw${})
+		$if .namespaced$Invokes($.NewGetAction|raw$($.type|allLowercasePlural$Resource, c.ns, name), &$.resultType|raw${})
-		$else$Invokes($.NewRootGetAction|raw$($.type|allLowercasePlural$Resource, name), &$.type|raw${})$end$
+		$else$Invokes($.NewRootGetAction|raw$($.type|allLowercasePlural$Resource, name), &$.resultType|raw${})$end$
 	if obj == nil {
 		return nil, err
 	}
-	return obj.(*$.type|raw$), err
+	return obj.(*$.resultType|raw$), err
+}
+`
+
+var getSubresourceTemplate = `
+// Get takes name of the $.type|private$, and returns the corresponding $.resultType|private$ object, and an error if there is any.
+func (c *Fake$.type|publicPlural$) Get($.type|private$Name string, options $.GetOptions|raw$) (result *$.resultType|raw$, err error) {
+	obj, err := c.Fake.
+		$if .namespaced$Invokes($.NewGetSubresourceAction|raw$($.type|allLowercasePlural$Resource, c.ns, "$.subresourcePath$", $.type|private$Name), &$.resultType|raw${})
+		$else$Invokes($.NewRootGetAction|raw$($.type|allLowercasePlural$Resource, $.type|private$Name), &$.resultType|raw${})$end$
+	if obj == nil {
+		return nil, err
+	}
+	return obj.(*$.resultType|raw$), err
 }
 `
 
@@ -291,30 +403,55 @@ func (c *Fake$.type|publicPlural$) DeleteCollection(options *$.DeleteOptions|raw
 	return err
 }
 `
-
 var createTemplate = `
-// Create takes the representation of a $.type|private$ and creates it.  Returns the server's representation of the $.type|private$, and an error, if there is any.
+// Create takes the representation of a $.inputType|private$ and creates it.  Returns the server's representation of the $.resultType|private$, and an error, if there is any.
-func (c *Fake$.type|publicPlural$) Create($.type|private$ *$.type|raw$) (result *$.type|raw$, err error) {
+func (c *Fake$.type|publicPlural$) Create($.inputType|private$ *$.inputType|raw$) (result *$.resultType|raw$, err error) {
 	obj, err := c.Fake.
-		$if .namespaced$Invokes($.NewCreateAction|raw$($.type|allLowercasePlural$Resource, c.ns, $.type|private$), &$.type|raw${})
+		$if .namespaced$Invokes($.NewCreateAction|raw$($.inputType|allLowercasePlural$Resource, c.ns, $.inputType|private$), &$.resultType|raw${})
-		$else$Invokes($.NewRootCreateAction|raw$($.type|allLowercasePlural$Resource, $.type|private$), &$.type|raw${})$end$
+		$else$Invokes($.NewRootCreateAction|raw$($.inputType|allLowercasePlural$Resource, $.inputType|private$), &$.resultType|raw${})$end$
 	if obj == nil {
 		return nil, err
 	}
-	return obj.(*$.type|raw$), err
+	return obj.(*$.resultType|raw$), err
+}
+`
+
+var createSubresourceTemplate = `
+// Create takes the representation of a $.inputType|private$ and creates it.  Returns the server's representation of the $.resultType|private$, and an error, if there is any.
+func (c *Fake$.type|publicPlural$) Create($.type|private$Name string, $.inputType|private$ *$.inputType|raw$) (result *$.resultType|raw$, err error) {
+	obj, err := c.Fake.
+		$if .namespaced$Invokes($.NewCreateSubresourceAction|raw$($.type|allLowercasePlural$Resource, $.type|private$Name, "$.subresourcePath$", c.ns, $.inputType|private$), &$.resultType|raw${})
+		$else$Invokes($.NewRootCreateAction|raw$($.inputType|allLowercasePlural$Resource, $.inputType|private$), &$.resultType|raw${})$end$
+	if obj == nil {
+		return nil, err
+	}
+	return obj.(*$.resultType|raw$), err
 }
 `
 
 var updateTemplate = `
-// Update takes the representation of a $.type|private$ and updates it. Returns the server's representation of the $.type|private$, and an error, if there is any.
+// Update takes the representation of a $.inputType|private$ and updates it. Returns the server's representation of the $.resultType|private$, and an error, if there is any.
-func (c *Fake$.type|publicPlural$) Update($.type|private$ *$.type|raw$) (result *$.type|raw$, err error) {
+func (c *Fake$.type|publicPlural$) Update($.inputType|private$ *$.inputType|raw$) (result *$.resultType|raw$, err error) {
 	obj, err := c.Fake.
-		$if .namespaced$Invokes($.NewUpdateAction|raw$($.type|allLowercasePlural$Resource, c.ns, $.type|private$), &$.type|raw${})
+		$if .namespaced$Invokes($.NewUpdateAction|raw$($.inputType|allLowercasePlural$Resource, c.ns, $.inputType|private$), &$.resultType|raw${})
+		$else$Invokes($.NewRootUpdateAction|raw$($.inputType|allLowercasePlural$Resource, $.inputType|private$), &$.resultType|raw${})$end$
+	if obj == nil {
+		return nil, err
+	}
+	return obj.(*$.resultType|raw$), err
+}
+`
+
+var updateSubresourceTemplate = `
+// Update takes the representation of a $.inputType|private$ and updates it. Returns the server's representation of the $.resultType|private$, and an error, if there is any.
+func (c *Fake$.type|publicPlural$) Update($.type|private$Name string, $.inputType|private$ *$.inputType|raw$) (result *$.resultType|raw$, err error) {
+	obj, err := c.Fake.
+		$if .namespaced$Invokes($.NewUpdateSubresourceAction|raw$($.type|allLowercasePlural$Resource, "$.subresourcePath$", c.ns, $.inputType|private$), &$.inputType|raw${})
 		$else$Invokes($.NewRootUpdateAction|raw$($.type|allLowercasePlural$Resource, $.type|private$), &$.type|raw${})$end$
 	if obj == nil {
 		return nil, err
 	}
-	return obj.(*$.type|raw$), err
+	return obj.(*$.resultType|raw$), err
 }
 `
 
@@ -342,14 +479,14 @@ func (c *Fake$.type|publicPlural$) Watch(opts $.ListOptions|raw$) ($.watchInterf
 `
 
 var patchTemplate = `
-// Patch applies the patch and returns the patched $.type|private$.
+// Patch applies the patch and returns the patched $.resultType|private$.
-func (c *Fake$.type|publicPlural$) Patch(name string, pt $.PatchType|raw$, data []byte, subresources ...string) (result *$.type|raw$, err error) {
+func (c *Fake$.type|publicPlural$) Patch(name string, pt $.PatchType|raw$, data []byte, subresources ...string) (result *$.resultType|raw$, err error) {
 	obj, err := c.Fake.
-		$if .namespaced$Invokes($.NewPatchSubresourceAction|raw$($.type|allLowercasePlural$Resource, c.ns, name, data, subresources... ), &$.type|raw${})
+		$if .namespaced$Invokes($.NewPatchSubresourceAction|raw$($.type|allLowercasePlural$Resource, c.ns, name, data, subresources... ), &$.resultType|raw${})
-		$else$Invokes($.NewRootPatchSubresourceAction|raw$($.type|allLowercasePlural$Resource, name, data, subresources...), &$.type|raw${})$end$
+		$else$Invokes($.NewRootPatchSubresourceAction|raw$($.type|allLowercasePlural$Resource, name, data, subresources...), &$.resultType|raw${})$end$
 	if obj == nil {
 		return nil, err
 	}
-	return obj.(*$.type|raw$), err
+	return obj.(*$.resultType|raw$), err
 }
 `

staging/src/k8s.io/code-generator/cmd/client-gen/generators/generator_for_type.go

@@ -77,12 +77,61 @@ func (g *genClientForType) GenerateType(c *generator.Context, t *types.Type, w i
 	if err != nil {
 		return err
 	}
+	type extendedInterfaceMethod struct {
+		template string
+		args     map[string]interface{}
+	}
+	extendedMethods := []extendedInterfaceMethod{}
+	for _, e := range tags.Extensions {
+		inputType := *t
+		resultType := *t
+		// TODO: Extract this to some helper method as this code is copied into
+		// 2 other places.
+		if len(e.InputTypeOverride) > 0 {
+			if name, pkg := e.Input(); len(pkg) > 0 {
+				newType := c.Universe.Type(types.Name{Package: pkg, Name: name})
+				inputType = *newType
+			} else {
+				inputType.Name.Name = e.InputTypeOverride
+			}
+		}
+		if len(e.ResultTypeOverride) > 0 {
+			if name, pkg := e.Result(); len(pkg) > 0 {
+				newType := c.Universe.Type(types.Name{Package: pkg, Name: name})
+				resultType = *newType
+			} else {
+				resultType.Name.Name = e.ResultTypeOverride
+			}
+		}
+		var updatedVerbtemplate string
+		if _, exists := subresourceDefaultVerbTemplates[e.VerbType]; e.IsSubresource() && exists {
+			updatedVerbtemplate = e.VerbName + "(" + strings.TrimPrefix(subresourceDefaultVerbTemplates[e.VerbType], strings.Title(e.VerbType)+"(")
+		} else {
+			updatedVerbtemplate = e.VerbName + "(" + strings.TrimPrefix(defaultVerbTemplates[e.VerbType], strings.Title(e.VerbType)+"(")
+		}
+		extendedMethods = append(extendedMethods, extendedInterfaceMethod{
+			template: updatedVerbtemplate,
+			args: map[string]interface{}{
+				"type":          t,
+				"inputType":     &inputType,
+				"resultType":    &resultType,
+				"DeleteOptions": c.Universe.Type(types.Name{Package: "k8s.io/apimachinery/pkg/apis/meta/v1", Name: "DeleteOptions"}),
+				"ListOptions":   c.Universe.Type(types.Name{Package: "k8s.io/apimachinery/pkg/apis/meta/v1", Name: "ListOptions"}),
+				"GetOptions":    c.Universe.Type(types.Name{Package: "k8s.io/apimachinery/pkg/apis/meta/v1", Name: "GetOptions"}),
+				"PatchType":     c.Universe.Type(types.Name{Package: "k8s.io/apimachinery/pkg/types", Name: "PatchType"}),
+			},
+		})
+	}
 	m := map[string]interface{}{
 		"type":                 t,
+		"inputType":            t,
+		"resultType":           t,
 		"package":              pkg,
 		"Package":              namer.IC(pkg),
 		"namespaced":           !tags.NonNamespaced,
 		"Group":                namer.IC(g.group),
+		"subresource":          false,
+		"subresourcePath":      "",
 		"GroupVersion":         namer.IC(g.group) + namer.IC(g.version),
 		"DeleteOptions":        c.Universe.Type(types.Name{Package: "k8s.io/apimachinery/pkg/apis/meta/v1", Name: "DeleteOptions"}),
 		"ListOptions":          c.Universe.Type(types.Name{Package: "k8s.io/apimachinery/pkg/apis/meta/v1", Name: "ListOptions"}),
@@ -105,7 +154,16 @@ func (g *genClientForType) GenerateType(c *generator.Context, t *types.Type, w i
 		if !genStatus(t) {
 			tags.SkipVerbs = append(tags.SkipVerbs, "updateStatus")
 		}
-		sw.Do(generateInterface(tags), m)
+		interfaceSuffix := ""
+		if len(extendedMethods) > 0 {
+			interfaceSuffix = "\n"
+		}
+		sw.Do("\n"+generateInterface(tags)+interfaceSuffix, m)
+		// add extended verbs into interface
+		for _, v := range extendedMethods {
+			sw.Do(v.template+interfaceSuffix, v.args)
+		}
+
 	}
 	sw.Do(interfaceTemplate4, m)
 
@@ -150,9 +208,88 @@ func (g *genClientForType) GenerateType(c *generator.Context, t *types.Type, w i
 		sw.Do(patchTemplate, m)
 	}
 
+	// generate expansion methods
+	for _, e := range tags.Extensions {
+		inputType := *t
+		resultType := *t
+		if len(e.InputTypeOverride) > 0 {
+			if name, pkg := e.Input(); len(pkg) > 0 {
+				newType := c.Universe.Type(types.Name{Package: pkg, Name: name})
+				inputType = *newType
+			} else {
+				inputType.Name.Name = e.InputTypeOverride
+			}
+		}
+		if len(e.ResultTypeOverride) > 0 {
+			if name, pkg := e.Result(); len(pkg) > 0 {
+				newType := c.Universe.Type(types.Name{Package: pkg, Name: name})
+				resultType = *newType
+			} else {
+				resultType.Name.Name = e.ResultTypeOverride
+			}
+		}
+		m["inputType"] = &inputType
+		m["resultType"] = &resultType
+		m["subresourcePath"] = e.SubResourcePath
+
+		if e.HasVerb("get") {
+			if e.IsSubresource() {
+				sw.Do(adjustTemplate(e.VerbName, e.VerbType, getSubresourceTemplate), m)
+			} else {
+				sw.Do(adjustTemplate(e.VerbName, e.VerbType, getTemplate), m)
+			}
+		}
+
+		if e.HasVerb("list") {
+			if e.IsSubresource() {
+				sw.Do(adjustTemplate(e.VerbName, e.VerbType, listSubresourceTemplate), m)
+			} else {
+				sw.Do(adjustTemplate(e.VerbName, e.VerbType, listTemplate), m)
+			}
+		}
+
+		// TODO: Figure out schemantic for watching a sub-resource.
+		if e.HasVerb("watch") {
+			sw.Do(adjustTemplate(e.VerbName, e.VerbType, watchTemplate), m)
+		}
+
+		if e.HasVerb("create") {
+			if e.IsSubresource() {
+				sw.Do(adjustTemplate(e.VerbName, e.VerbType, createSubresourceTemplate), m)
+			} else {
+				sw.Do(adjustTemplate(e.VerbName, e.VerbType, createTemplate), m)
+			}
+		}
+
+		if e.HasVerb("update") {
+			if e.IsSubresource() {
+				sw.Do(adjustTemplate(e.VerbName, e.VerbType, updateSubresourceTemplate), m)
+			} else {
+				sw.Do(adjustTemplate(e.VerbName, e.VerbType, updateTemplate), m)
+			}
+		}
+
+		// TODO: Figure out schemantic for deleting a sub-resource (what arguments
+		// are passed, does it need two names? etc.
+		if e.HasVerb("delete") {
+			sw.Do(adjustTemplate(e.VerbName, e.VerbType, deleteTemplate), m)
+		}
+
+		if e.HasVerb("patch") {
+			sw.Do(adjustTemplate(e.VerbName, e.VerbType, patchTemplate), m)
+		}
+	}
+
 	return sw.Error()
 }
 
+// adjustTemplate adjust the origin verb template using the expansion name.
+// TODO: Make the verbs in templates parametrized so the strings.Replace() is
+// not needed.
+func adjustTemplate(name, verbType, template string) string {
+	return strings.Replace(template, " "+strings.Title(verbType), " "+name, -1)
+}
+
 func generateInterface(tags util.Tags) string {
 	// need an ordered list here to guarantee order of generated methods.
 	out := []string{}
@@ -164,16 +301,23 @@ func generateInterface(tags util.Tags) string {
 	return strings.Join(out, "\n")
 }
 
+var subresourceDefaultVerbTemplates = map[string]string{
+	"create": `Create($.type|private$Name string, $.inputType|private$ *$.inputType|raw$) (*$.resultType|raw$, error)`,
+	"list":   `List($.type|private$Name string, opts $.ListOptions|raw$) (*$.resultType|raw$List, error)`,
+	"update": `Update($.type|private$Name string, $.inputType|private$ *$.inputType|raw$) (*$.resultType|raw$, error)`,
+	"get":    `Get($.type|private$Name string, options $.GetOptions|raw$) (*$.resultType|raw$, error)`,
+}
+
 var defaultVerbTemplates = map[string]string{
-	"create":           `Create(*$.type|raw$) (*$.type|raw$, error)`,
+	"create":           `Create(*$.inputType|raw$) (*$.resultType|raw$, error)`,
-	"update":           `Update(*$.type|raw$) (*$.type|raw$, error)`,
+	"update":           `Update(*$.inputType|raw$) (*$.resultType|raw$, error)`,
 	"updateStatus":     `UpdateStatus(*$.type|raw$) (*$.type|raw$, error)`,
 	"delete":           `Delete(name string, options *$.DeleteOptions|raw$) error`,
 	"deleteCollection": `DeleteCollection(options *$.DeleteOptions|raw$, listOptions $.ListOptions|raw$) error`,
-	"get":              `Get(name string, options $.GetOptions|raw$) (*$.type|raw$, error)`,
+	"get":              `Get(name string, options $.GetOptions|raw$) (*$.resultType|raw$, error)`,
-	"list":             `List(opts $.ListOptions|raw$) (*$.type|raw$List, error)`,
+	"list":             `List(opts $.ListOptions|raw$) (*$.resultType|raw$List, error)`,
 	"watch":            `Watch(opts $.ListOptions|raw$) ($.watchInterface|raw$, error)`,
-	"patch":            `Patch(name string, pt $.PatchType|raw$, data []byte, subresources ...string) (result *$.type|raw$, err error)`,
+	"patch":            `Patch(name string, pt $.PatchType|raw$, data []byte, subresources ...string) (result *$.resultType|raw$, err error)`,
 }
 
 // group client will implement this interface.
@@ -238,11 +382,10 @@ func new$.type|publicPlural$(c *$.GroupVersion$Client) *$.type|privatePlural$ {
 	}
 }
 `
-
 var listTemplate = `
-// List takes label and field selectors, and returns the list of $.type|publicPlural$ that match those selectors.
+// List takes label and field selectors, and returns the list of $.resultType|publicPlural$ that match those selectors.
-func (c *$.type|privatePlural$) List(opts $.ListOptions|raw$) (result *$.type|raw$List, err error) {
+func (c *$.type|privatePlural$) List(opts $.ListOptions|raw$) (result *$.resultType|raw$List, err error) {
-	result = &$.type|raw$List{}
+	result = &$.resultType|raw$List{}
 	err = c.client.Get().
 		$if .namespaced$Namespace(c.ns).$end$
 		Resource("$.type|resource$").
@@ -252,10 +395,27 @@ func (c *$.type|privatePlural$) List(opts $.ListOptions|raw$) (result *$.type|ra
 	return
 }
 `
+
+var listSubresourceTemplate = `
+// List takes $.type|raw$ name, label and field selectors, and returns the list of $.resultType|publicPlural$ that match those selectors.
+func (c *$.type|privatePlural$) List($.type|private$Name string, opts $.ListOptions|raw$) (result *$.resultType|raw$List, err error) {
+	result = &$.resultType|raw$List{}
+	err = c.client.Get().
+		$if .namespaced$Namespace(c.ns).$end$
+		Resource("$.type|resource$").
+		Name($.type|private$Name).
+		SubResource("$.subresourcePath$").
+		VersionedParams(&opts, $.schemeParameterCodec|raw$).
+		Do().
+		Into(result)
+	return
+}
+`
+
 var getTemplate = `
-// Get takes name of the $.type|private$, and returns the corresponding $.type|private$ object, and an error if there is any.
+// Get takes name of the $.type|private$, and returns the corresponding $.resultType|private$ object, and an error if there is any.
-func (c *$.type|privatePlural$) Get(name string, options $.GetOptions|raw$) (result *$.type|raw$, err error) {
+func (c *$.type|privatePlural$) Get(name string, options $.GetOptions|raw$) (result *$.resultType|raw$, err error) {
-	result = &$.type|raw${}
+	result = &$.resultType|raw${}
 	err = c.client.Get().
 		$if .namespaced$Namespace(c.ns).$end$
 		Resource("$.type|resource$").
@@ -267,6 +427,22 @@ func (c *$.type|privatePlural$) Get(name string, options $.GetOptions|raw$) (res
 }
 `
 
+var getSubresourceTemplate = `
+// Get takes name of the $.type|private$, and returns the corresponding $.resultType|raw$ object, and an error if there is any.
+func (c *$.type|privatePlural$) Get($.type|private$Name string, options $.GetOptions|raw$) (result *$.resultType|raw$, err error) {
+	result = &$.resultType|raw${}
+	err = c.client.Get().
+		$if .namespaced$Namespace(c.ns).$end$
+		Resource("$.type|resource$").
+		Name($.type|private$Name).
+		SubResource("$.subresourcePath$").
+		VersionedParams(&options, $.schemeParameterCodec|raw$).
+		Do().
+		Into(result)
+	return
+}
+`
+
 var deleteTemplate = `
 // Delete takes name of the $.type|private$ and deletes it. Returns an error if one occurs.
 func (c *$.type|privatePlural$) Delete(name string, options *$.DeleteOptions|raw$) error {
@@ -293,14 +469,46 @@ func (c *$.type|privatePlural$) DeleteCollection(options *$.DeleteOptions|raw$,
 }
 `
 
-var createTemplate = `
+var createSubresourceTemplate = `
-// Create takes the representation of a $.type|private$ and creates it.  Returns the server's representation of the $.type|private$, and an error, if there is any.
+// Create takes the representation of a $.inputType|private$ and creates it.  Returns the server's representation of the $.resultType|private$, and an error, if there is any.
-func (c *$.type|privatePlural$) Create($.type|private$ *$.type|raw$) (result *$.type|raw$, err error) {
+func (c *$.type|privatePlural$) Create($.type|private$Name string, $.inputType|private$ *$.inputType|raw$) (result *$.resultType|raw$, err error) {
-	result = &$.type|raw${}
+	result = &$.resultType|raw${}
 	err = c.client.Post().
 		$if .namespaced$Namespace(c.ns).$end$
 		Resource("$.type|resource$").
-		Body($.type|private$).
+		Name($.type|private$Name).
+		SubResource("$.subresourcePath$").
+		Body($.inputType|private$).
+		Do().
+		Into(result)
+	return
+}
+`
+
+var createTemplate = `
+// Create takes the representation of a $.inputType|private$ and creates it.  Returns the server's representation of the $.resultType|private$, and an error, if there is any.
+func (c *$.type|privatePlural$) Create($.inputType|private$ *$.inputType|raw$) (result *$.resultType|raw$, err error) {
+	result = &$.resultType|raw${}
+	err = c.client.Post().
+		$if .namespaced$Namespace(c.ns).$end$
+		Resource("$.type|resource$").
+		Body($.inputType|private$).
+		Do().
+		Into(result)
+	return
+}
+`
+
+var updateSubresourceTemplate = `
+// Update takes the top resource name and the representation of a $.inputType|private$ and updates it. Returns the server's representation of the $.resultType|private$, and an error, if there is any.
+func (c *$.type|privatePlural$) Update($.type|private$Name string, $.inputType|private$ *$.inputType|raw$) (result *$.resultType|raw$, err error) {
+	result = &$.resultType|raw${}
+	err = c.client.Put().
+		$if .namespaced$Namespace(c.ns).$end$
+		Resource("$.type|resource$").
+		Name($.type|private$Name).
+		SubResource("$.subresourcePath$").
+		Body($.inputType|private$).
 		Do().
 		Into(result)
 	return
@@ -308,14 +516,14 @@ func (c *$.type|privatePlural$) Create($.type|private$ *$.type|raw$) (result *$.
 `
 
 var updateTemplate = `
-// Update takes the representation of a $.type|private$ and updates it. Returns the server's representation of the $.type|private$, and an error, if there is any.
+// Update takes the representation of a $.inputType|private$ and updates it. Returns the server's representation of the $.resultType|private$, and an error, if there is any.
-func (c *$.type|privatePlural$) Update($.type|private$ *$.type|raw$) (result *$.type|raw$, err error) {
+func (c *$.type|privatePlural$) Update($.inputType|private$ *$.inputType|raw$) (result *$.resultType|raw$, err error) {
-	result = &$.type|raw${}
+	result = &$.resultType|raw${}
 	err = c.client.Put().
 		$if .namespaced$Namespace(c.ns).$end$
 		Resource("$.type|resource$").
-		Name($.type|private$.Name).
+		Name($.inputType|private$.Name).
-		Body($.type|private$).
+		Body($.inputType|private$).
 		Do().
 		Into(result)
 	return
@@ -353,9 +561,9 @@ func (c *$.type|privatePlural$) Watch(opts $.ListOptions|raw$) ($.watchInterface
 `
 
 var patchTemplate = `
-// Patch applies the patch and returns the patched $.type|private$.
+// Patch applies the patch and returns the patched $.resultType|private$.
-func (c *$.type|privatePlural$) Patch(name string, pt $.PatchType|raw$, data []byte, subresources ...string) (result *$.type|raw$, err error) {
+func (c *$.type|privatePlural$) Patch(name string, pt $.PatchType|raw$, data []byte, subresources ...string) (result *$.resultType|raw$, err error) {
-	result = &$.type|raw${}
+	result = &$.resultType|raw${}
 	err = c.client.Patch(pt).
 		$if .namespaced$Namespace(c.ns).$end$
 		Resource("$.type|resource$").

staging/src/k8s.io/code-generator/cmd/client-gen/generators/util/tags.go

@@ -32,6 +32,7 @@ var supportedTags = []string{
 	"genclient:skipVerbs",
 	"genclient:noStatus",
 	"genclient:readonly",
+	"genclient:method",
 }
 
 // SupportedVerbs is a list of supported verbs for +onlyVerbs and +skipVerbs.
@@ -54,6 +55,96 @@ var ReadonlyVerbs = []string{
 	"watch",
 }
 
+// genClientPrefix is the default prefix for all genclient tags.
+const genClientPrefix = "genclient:"
+
+// unsupportedExtensionVerbs is a list of verbs we don't support generating
+// extension client functions for.
+var unsupportedExtensionVerbs = []string{
+	"updateStatus",
+	"deleteCollection",
+	"watch",
+	"delete",
+}
+
+// inputTypeSupportedVerbs is a list of verb types that supports overriding the
+// input argument type.
+var inputTypeSupportedVerbs = []string{
+	"create",
+	"update",
+}
+
+// resultTypeSupportedVerbs is a list of verb types that supports overriding the
+// resulting type.
+var resultTypeSupportedVerbs = []string{
+	"create",
+	"update",
+	"get",
+	"list",
+	"patch",
+}
+
+// Extensions allows to extend the default set of client verbs
+// (CRUD+watch+patch+list+deleteCollection) for a given type with custom defined
+// verbs. Custom verbs can have custom input and result types and also allow to
+// use a sub-resource in a request instead of top-level resource type.
+//
+// Example:
+//
+// +genclient:method=UpdateScale,verb=update,subresource=scale,input=Scale,result=Scale
+//
+// type ReplicaSet struct { ... }
+//
+// The 'method=UpdateScale' is the name of the client function.
+// The 'verb=update' here means the client function will use 'PUT' action.
+// The 'subresource=scale' means we will use SubResource template to generate this client function.
+// The 'input' is the input type used for creation (function argument).
+// The 'result' (not needed in this case) is the result type returned from the
+// client function.
+//
+type extension struct {
+	// VerbName is the name of the custom verb (Scale, Instantiate, etc..)
+	VerbName string
+	// VerbType is the type of the verb (only verbs from SupportedVerbs are
+	// supported)
+	VerbType string
+	// SubResourcePath defines a path to a sub-resource to use in the request.
+	// (optional)
+	SubResourcePath string
+	// InputTypeOverride overrides the input parameter type for the verb. By
+	// default the original type is used. Overriding the input type only works for
+	// "create" and "update" verb types. The given type must exists in the same
+	// package as the original type.
+	// (optional)
+	InputTypeOverride string
+	// ResultTypeOverride overrides the resulting object type for the verb. By
+	// default the original type is used. Overriding the result type works.
+	// (optional)
+	ResultTypeOverride string
+}
+
+// IsSubresource indicates if this extension should generate the sub-resource.
+func (e *extension) IsSubresource() bool {
+	return len(e.SubResourcePath) > 0
+}
+
+// HasVerb checks if the extension matches the given verb.
+func (e *extension) HasVerb(verb string) bool {
+	return e.VerbType == verb
+}
+
+// Input returns the input override package path and the type.
+func (e *extension) Input() (string, string) {
+	parts := strings.Split(e.InputTypeOverride, ".")
+	return parts[len(parts)-1], strings.Join(parts[0:len(parts)-1], ".")
+}
+
+// Result returns the result override package path and the type.
+func (e *extension) Result() (string, string) {
+	parts := strings.Split(e.ResultTypeOverride, ".")
+	return parts[len(parts)-1], strings.Join(parts[0:len(parts)-1], ".")
+}
+
 // Tags represents a genclient configuration for a single type.
 type Tags struct {
 	// +genclient
@@ -67,6 +158,8 @@ type Tags struct {
 	// +genclient:skipVerbs=get,update
 	// +genclient:onlyVerbs=create,delete
 	SkipVerbs []string
+	// +genclient:method=UpdateScale,verb=update,subresource=scale,input=Scale,result=Scale
+	Extensions []extension
 }
 
 // HasVerb returns true if we should include the given verb in final client interface and
@@ -103,25 +196,25 @@ func ParseClientGenTags(lines []string) (Tags, error) {
 	if len(value) > 0 && len(value[0]) > 0 {
 		return ret, fmt.Errorf("+genclient=%s is invalid, use //+genclient if you want to generate client or omit it when you want to disable generation", value)
 	}
-	_, ret.NonNamespaced = values["genclient:nonNamespaced"]
+	_, ret.NonNamespaced = values[genClientPrefix+"nonNamespaced"]
 	// Check the old format and error when used
 	if value := values["nonNamespaced"]; len(value) > 0 && len(value[0]) > 0 {
 		return ret, fmt.Errorf("+nonNamespaced=%s is invalid, use //+genclient:nonNamespaced instead", value[0])
 	}
-	_, ret.NoVerbs = values["genclient:noVerbs"]
+	_, ret.NoVerbs = values[genClientPrefix+"noVerbs"]
-	_, ret.NoStatus = values["genclient:noStatus"]
+	_, ret.NoStatus = values[genClientPrefix+"noStatus"]
 	onlyVerbs := []string{}
-	if _, isReadonly := values["genclient:readonly"]; isReadonly {
+	if _, isReadonly := values[genClientPrefix+"readonly"]; isReadonly {
 		onlyVerbs = ReadonlyVerbs
 	}
 	// Check the old format and error when used
 	if value := values["readonly"]; len(value) > 0 && len(value[0]) > 0 {
 		return ret, fmt.Errorf("+readonly=%s is invalid, use //+genclient:readonly instead", value[0])
 	}
-	if v, exists := values["genclient:skipVerbs"]; exists {
+	if v, exists := values[genClientPrefix+"skipVerbs"]; exists {
 		ret.SkipVerbs = strings.Split(v[0], ",")
 	}
-	if v, exists := values["genclient:onlyVerbs"]; exists || len(onlyVerbs) > 0 {
+	if v, exists := values[genClientPrefix+"onlyVerbs"]; exists || len(onlyVerbs) > 0 {
 		if len(v) > 0 {
 			onlyVerbs = append(onlyVerbs, strings.Split(v[0], ",")...)
 		}
@@ -146,16 +239,101 @@ func ParseClientGenTags(lines []string) (Tags, error) {
 		}
 		ret.SkipVerbs = skipVerbs
 	}
+	var err error
+	if ret.Extensions, err = parseClientExtensions(values); err != nil {
+		return ret, err
+	}
 	return ret, validateClientGenTags(values)
 }
 
+func parseClientExtensions(tags map[string][]string) ([]extension, error) {
+	var ret []extension
+	for name, values := range tags {
+		if !strings.HasPrefix(name, genClientPrefix+"method") {
+			continue
+		}
+		for _, value := range values {
+			// the value comes in this form: "Foo,verb=create"
+			ext := extension{}
+			parts := strings.Split(value, ",")
+			if len(parts) == 0 {
+				return nil, fmt.Errorf("invalid of empty extension verb name: %q", value)
+			}
+			// The first part represents the name of the extension
+			ext.VerbName = parts[0]
+			if len(ext.VerbName) == 0 {
+				return nil, fmt.Errorf("must specify a verb name (// +genclient:method=Foo,verb=create)")
+			}
+			// Parse rest of the arguments
+			params := parts[1:]
+			for _, p := range params {
+				parts := strings.Split(p, "=")
+				if len(parts) != 2 {
+					return nil, fmt.Errorf("invalid extension tag specification %q", p)
+				}
+				key, val := strings.TrimSpace(parts[0]), strings.TrimSpace(parts[1])
+				if len(val) == 0 {
+					return nil, fmt.Errorf("empty value of %q for %q extension", key, ext.VerbName)
+				}
+				switch key {
+				case "verb":
+					ext.VerbType = val
+				case "subresource":
+					ext.SubResourcePath = val
+				case "input":
+					ext.InputTypeOverride = val
+				case "result":
+					ext.ResultTypeOverride = val
+				default:
+					return nil, fmt.Errorf("unknown extension configuration key %q", key)
+				}
+			}
+			// Validate resulting extension configuration
+			if len(ext.VerbType) == 0 {
+				return nil, fmt.Errorf("verb type must be specified (use '// +genclient:method=%s,verb=create')", ext.VerbName)
+			}
+			if len(ext.ResultTypeOverride) > 0 {
+				supported := false
+				for _, v := range resultTypeSupportedVerbs {
+					if ext.VerbType == v {
+						supported = true
+						break
+					}
+				}
+				if !supported {
+					return nil, fmt.Errorf("%s: result type is not supported for %q verbs (supported verbs: %#v)", ext.VerbName, ext.VerbType, resultTypeSupportedVerbs)
+				}
+			}
+			if len(ext.InputTypeOverride) > 0 {
+				supported := false
+				for _, v := range inputTypeSupportedVerbs {
+					if ext.VerbType == v {
+						supported = true
+						break
+					}
+				}
+				if !supported {
+					return nil, fmt.Errorf("%s: input type is not supported for %q verbs (supported verbs: %#v)", ext.VerbName, ext.VerbType, inputTypeSupportedVerbs)
+				}
+			}
+			for _, t := range unsupportedExtensionVerbs {
+				if ext.VerbType == t {
+					return nil, fmt.Errorf("verb %q is not supported by extension generator", ext.VerbType)
+				}
+			}
+			ret = append(ret, ext)
+		}
+	}
+	return ret, nil
+}
+
 // validateTags validates that only supported genclient tags were provided.
 func validateClientGenTags(values map[string][]string) error {
 	for _, k := range supportedTags {
 		delete(values, k)
 	}
 	for key := range values {
-		if strings.HasPrefix(key, "genclient") {
+		if strings.HasPrefix(key, strings.TrimSuffix(genClientPrefix, ":")) {
 			return errors.New("unknown tag detected: " + key)
 		}
 	}

staging/src/k8s.io/code-generator/cmd/client-gen/generators/util/tags_test.go

@@ -82,3 +82,67 @@ func TestParseTags(t *testing.T) {
 		}
 	}
 }
+
+func TestParseTagsExtension(t *testing.T) {
+	testCases := map[string]struct {
+		lines              []string
+		expectedExtensions []extension
+		expectError        bool
+	}{
+		"simplest extension": {
+			lines:              []string{`+genclient:method=Foo,verb=create`},
+			expectedExtensions: []extension{{VerbName: "Foo", VerbType: "create"}},
+		},
+		"multiple extensions": {
+			lines:              []string{`+genclient:method=Foo,verb=create`, `+genclient:method=Bar,verb=get`},
+			expectedExtensions: []extension{{VerbName: "Foo", VerbType: "create"}, {VerbName: "Bar", VerbType: "get"}},
+		},
+		"extension without verb": {
+			lines:       []string{`+genclient:method`},
+			expectError: true,
+		},
+		"extension without verb type": {
+			lines:       []string{`+genclient:method=Foo`},
+			expectError: true,
+		},
+		"sub-resource extension": {
+			lines:              []string{`+genclient:method=Foo,verb=create,subresource=bar`},
+			expectedExtensions: []extension{{VerbName: "Foo", VerbType: "create", SubResourcePath: "bar"}},
+		},
+		"output type extension": {
+			lines:              []string{`+genclient:method=Foos,verb=list,result=Bars`},
+			expectedExtensions: []extension{{VerbName: "Foos", VerbType: "list", ResultTypeOverride: "Bars"}},
+		},
+		"input type extension": {
+			lines:              []string{`+genclient:method=Foo,verb=update,input=Bar`},
+			expectedExtensions: []extension{{VerbName: "Foo", VerbType: "update", InputTypeOverride: "Bar"}},
+		},
+		"unknown verb type extension": {
+			lines:              []string{`+genclient:method=Foo,verb=explode`},
+			expectedExtensions: nil,
+			expectError:        true,
+		},
+		"invalid verb extension": {
+			lines:              []string{`+genclient:method=Foo,unknown=bar`},
+			expectedExtensions: nil,
+			expectError:        true,
+		},
+		"empty verb extension subresource": {
+			lines:              []string{`+genclient:method=Foo,verb=get,subresource=`},
+			expectedExtensions: nil,
+			expectError:        true,
+		},
+	}
+	for key, c := range testCases {
+		result, err := ParseClientGenTags(c.lines)
+		if err != nil && !c.expectError {
+			t.Fatalf("[%s] unexpected error: %v", key, err)
+		}
+		if err != nil && c.expectError {
+			t.Logf("[%s] got expected error: %+v", key, err)
+		}
+		if !c.expectError && !reflect.DeepEqual(result.Extensions, c.expectedExtensions) {
+			t.Errorf("[%s] expected %#+v to be %#+v", key, result.Extensions, c.expectedExtensions)
+		}
+	}
+}