validation-gen: Nix emit-register-funcs, use a tag

Get rid of flag `--emit-register-funcs` and use a per-pkg tag.

Set `+k8s:validation-gen-scheme-registry=nil` to disable register
function generation for a pkg.

staging/src/k8s.io/code-generator/cmd/validation-gen/main.go

@@ -98,8 +98,6 @@ type Args struct {
 	// kind/path/errorType/origin) plus a required reason.
 	TestAllowlist string
 
-	EmitRegisterFuncs bool
-
 	apidefinitions.LintArgs
 }
 
@@ -119,8 +117,6 @@ func (args *Args) AddFlags(fs *pflag.FlagSet) {
 		"prefix prepended to every emitted test fixture filename; useful for marking files via a linguist-generated gitattributes pattern (e.g. \"zz_generated.\")")
 	fs.StringVar(&args.TestAllowlist, "test-allowlist", "",
 		"path to a YAML config file of rule-level filters to exclude from coverage fixture generation; only meaningful with --test-output-root")
-	fs.BoolVar(&args.EmitRegisterFuncs, "emit-register-funcs", true,
-		"if true, emit the registration function")
 	apidefinitions.AddFlags(&args.LintArgs, fs)
 }
 

staging/src/k8s.io/code-generator/cmd/validation-gen/targets.go

@@ -37,9 +37,22 @@ import (
 
 // These are the comment tags that carry parameters for validation generation.
 const (
-	mainTagName           = "k8s:validation-gen"                 // defines which types to generate validation for
-	schemeRegistryTagName = "k8s:validation-gen-scheme-registry" // defaults to k8s.io/apimachinery/pkg.runtime.Scheme
-	testFixtureTagName    = "k8s:validation-gen-test-fixture"    // if set, generate go test files for test fixtures.  Supported values: "validateFalse".
+	// Defines which types to generate validation for.  There are two places
+	// this can be used:
+	//   Per-package:
+	//     * "*": generate validation for all types in this package
+	//	   * "FooBar": generate validation for all types with a field named "FooBar"
+	//   Per-type:
+	//	   * "true": generate validation for this type
+	//	   * "false": do not generate validation for this type
+	mainTagName = "k8s:validation-gen"
+	// Defines the type of the scheme used to register validations. Defaults to
+	// "k8s.io/apimachinery/pkg.runtime.Scheme", but can be set to another type
+	// (e.g. in tests), or set to "nil" to disable scheme registration for this
+	// package.
+	schemeRegistryTagName = "k8s:validation-gen-scheme-registry"
+	// If set, generate go test files for test fixtures.  Supported values: "validateFalse".
+	testFixtureTagName = "k8s:validation-gen-test-fixture"
 
 	// name of the subresource that this type represents and can validate declaratively.
 	isSubresourceTagName = "k8s:isSubresource"
@@ -114,7 +127,7 @@ func checkMainTag(comments []string, require ...string) bool {
 	return reflect.DeepEqual(valueStrings, require)
 }
 
-func schemeRegistryTag(pkg *types.Package) types.Name {
+func schemeRegistryTag(pkg *types.Package) (types.Name, bool) {
 	// TODO: convert to extractAndParseTag() and update all callers to use quoted values
 	tags, err := gengo.ExtractFunctionStyleCommentTags("+", []string{schemeRegistryTagName}, pkg.Comments)
 	if err != nil {
@@ -122,12 +135,17 @@ func schemeRegistryTag(pkg *types.Package) types.Name {
 	}
 	values, found := tags[schemeRegistryTagName]
 	if !found || len(values) == 0 {
-		return schemeType // default
+		return schemeType, true // default
 	}
 	if len(values) > 1 {
 		panic(fmt.Sprintf("Package %q contains more than one usage of %q", pkg.Path, schemeRegistryTagName))
 	}
-	return types.ParseFullyQualifiedName(values[0].Value)
+	val := values[0].Value
+	if val == "nil" {
+		// no registration wanted for this package
+		return types.Name{}, false
+	}
+	return types.ParseFullyQualifiedName(val), true
 }
 
 func isSubresourceTag(t *types.Type) (string, bool) {
@@ -322,7 +340,7 @@ func GetTargets(context *generator.Context, args *Args) []generator.Target {
 
 		pkg := context.Universe[input]
 
-		schemeRegistry := schemeRegistryTag(pkg)
+		schemeRegistry, registerThisPkg := schemeRegistryTag(pkg)
 
 		typesWith, found := validationTypeMatch(pkg, idOpts)
 		if !found {
@@ -423,7 +441,7 @@ func GetTargets(context *generator.Context, args *Args) []generator.Target {
 
 				GeneratorsFunc: func(c *generator.Context) (generators []generator.Generator) {
 					generators = []generator.Generator{
-						NewGenValidations(args.OutputFile, pkg.Path, rootTypes, td, inputToPkg, schemeRegistry, args.EmitRegisterFuncs),
+						NewGenValidations(args.OutputFile, pkg.Path, rootTypes, td, inputToPkg, schemeRegistry, registerThisPkg),
 					}
 					testFixtureTags := testFixtureTag(pkg)
 					if testFixtureTags.Len() > 0 {

staging/src/k8s.io/code-generator/cmd/validation-gen/validation.go

@@ -63,28 +63,28 @@ var (
 // genValidations produces a file with autogenerated validations.
 type genValidations struct {
 	generator.GoGenerator
-	outputPackage     string
-	inputToPkg        map[string]string // Maps input packages to generated validation packages
-	rootTypes         []*types.Type
-	discovered        *typeDiscoverer
-	imports           namer.ImportTracker
-	schemeRegistry    types.Name
-	emitRegisterFuncs bool
+	outputPackage    string
+	inputToPkg       map[string]string // Maps input packages to generated validation packages
+	rootTypes        []*types.Type
+	discovered       *typeDiscoverer
+	imports          namer.ImportTracker
+	schemeRegistry   types.Name
+	emitRegisterFunc bool
 }
 
 // NewGenValidations creates a new generator for the specified package.
-func NewGenValidations(outputFilename, outputPackage string, rootTypes []*types.Type, discovered *typeDiscoverer, inputToPkg map[string]string, schemeRegistry types.Name, emitRegisterFuncs bool) generator.Generator {
+func NewGenValidations(outputFilename, outputPackage string, rootTypes []*types.Type, discovered *typeDiscoverer, inputToPkg map[string]string, schemeRegistry types.Name, emitRegisterFunc bool) generator.Generator {
 	return &genValidations{
 		GoGenerator: generator.GoGenerator{
 			OutputFilename: outputFilename,
 		},
-		outputPackage:     outputPackage,
-		inputToPkg:        inputToPkg,
-		rootTypes:         rootTypes,
-		discovered:        discovered,
-		imports:           generator.NewImportTrackerForPackage(outputPackage),
-		schemeRegistry:    schemeRegistry,
-		emitRegisterFuncs: emitRegisterFuncs,
+		outputPackage:    outputPackage,
+		inputToPkg:       inputToPkg,
+		rootTypes:        rootTypes,
+		discovered:       discovered,
+		imports:          generator.NewImportTrackerForPackage(outputPackage),
+		schemeRegistry:   schemeRegistry,
+		emitRegisterFunc: emitRegisterFunc,
 	}
 }
 
@@ -129,7 +129,7 @@ func (g *genValidations) isOtherPackage(pkg string) bool {
 func (g *genValidations) Init(c *generator.Context, w io.Writer) error {
 	klog.V(5).Infof("emitting registration code")
 	sw := generator.NewSnippetWriter(w, c, "$", "$")
-	if g.emitRegisterFuncs {
+	if g.emitRegisterFunc {
 		g.emitRegisterFunction(c, g.schemeRegistry, sw)
 	}
 	if err := sw.Error(); err != nil {