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tailscale/cmd/viewer/viewer.go

604 lines
20 KiB
Go

// Copyright (c) Tailscale Inc & AUTHORS
// SPDX-License-Identifier: BSD-3-Clause
// Viewer is a tool to automate the creation of "view" wrapper types that
// provide read-only accessor methods to underlying fields.
package main
import (
"bytes"
"flag"
"fmt"
"go/types"
"html/template"
"log"
"os"
"slices"
"strings"
"tailscale.com/util/codegen"
"tailscale.com/util/must"
)
const viewTemplateStr = `{{define "common"}}
// View returns a readonly view of {{.StructName}}.
func (p *{{.StructName}}{{.TypeParamNames}}) View() {{.ViewName}}{{.TypeParamNames}} {
return {{.ViewName}}{{.TypeParamNames}}{ж: p}
}
// {{.ViewName}}{{.TypeParamNames}} provides a read-only view over {{.StructName}}{{.TypeParamNames}}.
//
// Its methods should only be called if ` + "`Valid()`" + ` returns true.
type {{.ViewName}}{{.TypeParams}} struct {
// ж is the underlying mutable value, named with a hard-to-type
// character that looks pointy like a pointer.
// It is named distinctively to make you think of how dangerous it is to escape
// to callers. You must not let callers be able to mutate it.
ж *{{.StructName}}{{.TypeParamNames}}
}
// Valid reports whether underlying value is non-nil.
func (v {{.ViewName}}{{.TypeParamNames}}) Valid() bool { return v.ж != nil }
// AsStruct returns a clone of the underlying value which aliases no memory with
// the original.
func (v {{.ViewName}}{{.TypeParamNames}}) AsStruct() *{{.StructName}}{{.TypeParamNames}}{
if v.ж == nil {
return nil
}
return v.ж.Clone()
}
func (v {{.ViewName}}{{.TypeParamNames}}) MarshalJSON() ([]byte, error) { return json.Marshal(v.ж) }
func (v *{{.ViewName}}{{.TypeParamNames}}) UnmarshalJSON(b []byte) error {
if v.ж != nil {
return errors.New("already initialized")
}
if len(b) == 0 {
return nil
}
var x {{.StructName}}{{.TypeParamNames}}
if err := json.Unmarshal(b, &x); err != nil {
return err
}
v.ж=&x
return nil
}
{{end}}
{{define "valueField"}}func (v {{.ViewName}}{{.TypeParamNames}}) {{.FieldName}}() {{.FieldType}} { return v.ж.{{.FieldName}} }
{{end}}
{{define "byteSliceField"}}func (v {{.ViewName}}{{.TypeParamNames}}) {{.FieldName}}() views.ByteSlice[{{.FieldType}}] { return views.ByteSliceOf(v.ж.{{.FieldName}}) }
{{end}}
{{define "sliceField"}}func (v {{.ViewName}}{{.TypeParamNames}}) {{.FieldName}}() views.Slice[{{.FieldType}}] { return views.SliceOf(v.ж.{{.FieldName}}) }
{{end}}
{{define "viewSliceField"}}func (v {{.ViewName}}{{.TypeParamNames}}) {{.FieldName}}() views.SliceView[{{.FieldType}},{{.FieldViewName}}] { return views.SliceOfViews[{{.FieldType}},{{.FieldViewName}}](v.ж.{{.FieldName}}) }
{{end}}
{{define "viewField"}}func (v {{.ViewName}}{{.TypeParamNames}}) {{.FieldName}}() {{.FieldViewName}} { return v.ж.{{.FieldName}}.View() }
{{end}}
{{define "makeViewField"}}func (v {{.ViewName}}{{.TypeParamNames}}) {{.FieldName}}() {{.FieldViewName}} { return {{.MakeViewFnName}}(&v.ж.{{.FieldName}}) }
{{end}}
{{define "valuePointerField"}}func (v {{.ViewName}}{{.TypeParamNames}}) {{.FieldName}}() {{.FieldType}} {
if v.ж.{{.FieldName}} == nil {
return nil
}
x := *v.ж.{{.FieldName}}
return &x
}
{{end}}
{{define "mapField"}}
func(v {{.ViewName}}{{.TypeParamNames}}) {{.FieldName}}() views.Map[{{.MapKeyType}},{{.MapValueType}}] { return views.MapOf(v.ж.{{.FieldName}})}
{{end}}
{{define "mapFnField"}}
func(v {{.ViewName}}{{.TypeParamNames}}) {{.FieldName}}() views.MapFn[{{.MapKeyType}},{{.MapValueType}},{{.MapValueView}}] { return views.MapFnOf(v.ж.{{.FieldName}}, func (t {{.MapValueType}}) {{.MapValueView}} {
return {{.MapFn}}
})}
{{end}}
{{define "mapSliceField"}}
func(v {{.ViewName}}{{.TypeParamNames}}) {{.FieldName}}() views.MapSlice[{{.MapKeyType}},{{.MapValueType}}] { return views.MapSliceOf(v.ж.{{.FieldName}}) }
{{end}}
{{define "unsupportedField"}}func(v {{.ViewName}}{{.TypeParamNames}}) {{.FieldName}}() {{.FieldType}} {panic("unsupported")}
{{end}}
{{define "stringFunc"}}func(v {{.ViewName}}{{.TypeParamNames}}) String() string { return v.ж.String() }
{{end}}
{{define "equalFunc"}}func(v {{.ViewName}}{{.TypeParamNames}}) Equal(v2 {{.ViewName}}{{.TypeParamNames}}) bool { return v.ж.Equal(v2.ж) }
{{end}}
`
var viewTemplate *template.Template
func init() {
viewTemplate = template.Must(template.New("view").Parse(viewTemplateStr))
}
func requiresCloning(t types.Type) (shallow, deep bool, base types.Type) {
switch v := t.(type) {
case *types.Pointer:
_, deep, base = requiresCloning(v.Elem())
return true, deep, base
case *types.Slice:
_, deep, base = requiresCloning(v.Elem())
return true, deep, base
}
p := codegen.ContainsPointers(t)
return p, p, t
}
func genView(buf *bytes.Buffer, it *codegen.ImportTracker, typ *types.Named, thisPkg *types.Package) {
t, ok := typ.Underlying().(*types.Struct)
if !ok || codegen.IsViewType(t) {
return
}
it.Import("encoding/json")
it.Import("errors")
args := struct {
StructName string
ViewName string
TypeParams string // e.g. [T constraints.Integer]
TypeParamNames string // e.g. [T]
FieldName string
FieldType string
FieldViewName string
MapKeyType string
MapValueType string
MapValueView string
MapFn string
// MakeViewFnName is the name of the function that accepts a value and returns a readonly view of it.
MakeViewFnName string
}{
StructName: typ.Obj().Name(),
ViewName: typ.Origin().Obj().Name() + "View",
}
typeParams := typ.Origin().TypeParams()
args.TypeParams, args.TypeParamNames = codegen.FormatTypeParams(typeParams, it)
writeTemplate := func(name string) {
if err := viewTemplate.ExecuteTemplate(buf, name, args); err != nil {
log.Fatal(err)
}
}
writeTemplate("common")
for i := range t.NumFields() {
f := t.Field(i)
fname := f.Name()
if !f.Exported() {
continue
}
args.FieldName = fname
fieldType := f.Type()
if codegen.IsInvalid(fieldType) {
continue
}
if !codegen.ContainsPointers(fieldType) || codegen.IsViewType(fieldType) || codegen.HasNoClone(t.Tag(i)) {
args.FieldType = it.QualifiedName(fieldType)
writeTemplate("valueField")
continue
}
switch underlying := fieldType.Underlying().(type) {
case *types.Slice:
slice := underlying
elem := slice.Elem()
switch elem.String() {
case "byte":
args.FieldType = it.QualifiedName(fieldType)
it.Import("tailscale.com/types/views")
writeTemplate("byteSliceField")
default:
args.FieldType = it.QualifiedName(elem)
it.Import("tailscale.com/types/views")
shallow, deep, base := requiresCloning(elem)
if deep {
switch elem.Underlying().(type) {
case *types.Pointer:
if _, isIface := base.Underlying().(*types.Interface); !isIface {
args.FieldViewName = appendNameSuffix(it.QualifiedName(base), "View")
writeTemplate("viewSliceField")
} else {
writeTemplate("unsupportedField")
}
continue
case *types.Interface:
if viewType := viewTypeForValueType(elem); viewType != nil {
args.FieldViewName = it.QualifiedName(viewType)
writeTemplate("viewSliceField")
continue
}
}
writeTemplate("unsupportedField")
continue
} else if shallow {
switch base.Underlying().(type) {
case *types.Basic, *types.Interface:
writeTemplate("unsupportedField")
default:
if _, isIface := base.Underlying().(*types.Interface); !isIface {
args.FieldViewName = appendNameSuffix(it.QualifiedName(base), "View")
writeTemplate("viewSliceField")
} else {
writeTemplate("unsupportedField")
}
}
continue
}
writeTemplate("sliceField")
}
continue
case *types.Struct, *types.Named:
strucT := underlying
args.FieldType = it.QualifiedName(fieldType)
if codegen.ContainsPointers(strucT) {
if viewType := viewTypeForValueType(fieldType); viewType != nil {
args.FieldViewName = it.QualifiedName(viewType)
writeTemplate("viewField")
continue
}
if viewType, makeViewFn := viewTypeForContainerType(fieldType); viewType != nil {
args.FieldViewName = it.QualifiedName(viewType)
args.MakeViewFnName = it.PackagePrefix(makeViewFn.Pkg()) + makeViewFn.Name()
writeTemplate("makeViewField")
continue
}
writeTemplate("unsupportedField")
continue
}
writeTemplate("valueField")
continue
case *types.Map:
m := underlying
args.FieldType = it.QualifiedName(fieldType)
shallow, deep, key := requiresCloning(m.Key())
if shallow || deep {
writeTemplate("unsupportedField")
continue
}
args.MapKeyType = it.QualifiedName(key)
mElem := m.Elem()
var template string
switch u := mElem.(type) {
case *types.Struct, *types.Named:
strucT := u
args.FieldType = it.QualifiedName(fieldType)
if codegen.ContainsPointers(strucT) {
args.MapFn = "t.View()"
template = "mapFnField"
args.MapValueType = it.QualifiedName(mElem)
args.MapValueView = appendNameSuffix(args.MapValueType, "View")
} else {
template = "mapField"
args.MapValueType = it.QualifiedName(mElem)
}
case *types.Basic:
template = "mapField"
args.MapValueType = it.QualifiedName(mElem)
case *types.Slice:
slice := u
sElem := slice.Elem()
switch x := sElem.(type) {
case *types.Basic, *types.Named:
sElem := it.QualifiedName(sElem)
args.MapValueView = fmt.Sprintf("views.Slice[%v]", sElem)
args.MapValueType = sElem
template = "mapSliceField"
case *types.Pointer:
ptr := x
pElem := ptr.Elem()
template = "unsupportedField"
if _, isIface := pElem.Underlying().(*types.Interface); !isIface {
switch pElem.(type) {
case *types.Struct, *types.Named:
ptrType := it.QualifiedName(ptr)
viewType := appendNameSuffix(it.QualifiedName(pElem), "View")
args.MapFn = fmt.Sprintf("views.SliceOfViews[%v,%v](t)", ptrType, viewType)
args.MapValueView = fmt.Sprintf("views.SliceView[%v,%v]", ptrType, viewType)
args.MapValueType = "[]" + ptrType
template = "mapFnField"
default:
template = "unsupportedField"
}
} else {
template = "unsupportedField"
}
default:
template = "unsupportedField"
}
case *types.Pointer:
ptr := u
pElem := ptr.Elem()
if _, isIface := pElem.Underlying().(*types.Interface); !isIface {
switch pElem.(type) {
case *types.Struct, *types.Named:
args.MapValueType = it.QualifiedName(ptr)
args.MapValueView = appendNameSuffix(it.QualifiedName(pElem), "View")
args.MapFn = "t.View()"
template = "mapFnField"
default:
template = "unsupportedField"
}
} else {
template = "unsupportedField"
}
case *types.Interface, *types.TypeParam:
if viewType := viewTypeForValueType(u); viewType != nil {
args.MapValueType = it.QualifiedName(u)
args.MapValueView = it.QualifiedName(viewType)
args.MapFn = "t.View()"
template = "mapFnField"
} else if !codegen.ContainsPointers(u) {
args.MapValueType = it.QualifiedName(mElem)
template = "mapField"
} else {
template = "unsupportedField"
}
default:
template = "unsupportedField"
}
writeTemplate(template)
continue
case *types.Pointer:
ptr := underlying
_, deep, base := requiresCloning(ptr)
if deep {
if _, isIface := base.Underlying().(*types.Interface); !isIface {
args.FieldType = it.QualifiedName(base)
args.FieldViewName = appendNameSuffix(args.FieldType, "View")
writeTemplate("viewField")
} else {
writeTemplate("unsupportedField")
}
} else {
args.FieldType = it.QualifiedName(ptr)
writeTemplate("valuePointerField")
}
continue
case *types.Interface:
// If fieldType is an interface with a "View() {ViewType}" method, it can be used to clone the field.
// This includes scenarios where fieldType is a constrained type parameter.
if viewType := viewTypeForValueType(underlying); viewType != nil {
args.FieldViewName = it.QualifiedName(viewType)
writeTemplate("viewField")
continue
}
}
writeTemplate("unsupportedField")
}
for i := range typ.NumMethods() {
f := typ.Method(i)
if !f.Exported() {
continue
}
sig, ok := f.Type().(*types.Signature)
if !ok {
continue
}
switch f.Name() {
case "Clone", "View":
continue // "AsStruct"
case "String":
writeTemplate("stringFunc")
continue
case "Equal":
if sig.Results().Len() == 1 && sig.Results().At(0).Type().String() == "bool" {
writeTemplate("equalFunc")
continue
}
}
}
fmt.Fprintf(buf, "\n")
buf.Write(codegen.AssertStructUnchanged(t, args.StructName, typeParams, "View", it))
}
func appendNameSuffix(name, suffix string) string {
if idx := strings.IndexRune(name, '['); idx != -1 {
// Insert suffix after the type name, but before type parameters.
return name[:idx] + suffix + name[idx:]
}
return name + suffix
}
func viewTypeForValueType(typ types.Type) types.Type {
if ptr, ok := typ.(*types.Pointer); ok {
return viewTypeForValueType(ptr.Elem())
}
viewMethod := codegen.LookupMethod(typ, "View")
if viewMethod == nil {
return nil
}
sig, ok := viewMethod.Type().(*types.Signature)
if !ok || sig.Results().Len() != 1 {
return nil
}
return sig.Results().At(0).Type()
}
func viewTypeForContainerType(typ types.Type) (*types.Named, *types.Func) {
// The container type should be an instantiated generic type,
// with its first type parameter specifying the element type.
containerType, ok := typ.(*types.Named)
if !ok || containerType.TypeArgs().Len() == 0 {
return nil, nil
}
// Look up the view type for the container type.
// It must include an additional type parameter specifying the element's view type.
// For example, Container[T] => ContainerView[T, V].
containerViewTypeName := containerType.Obj().Name() + "View"
containerViewTypeObj, ok := containerType.Obj().Pkg().Scope().Lookup(containerViewTypeName).(*types.TypeName)
if !ok {
return nil, nil
}
containerViewGenericType, ok := containerViewTypeObj.Type().(*types.Named)
if !ok || containerViewGenericType.TypeParams().Len() != containerType.TypeArgs().Len()+1 {
return nil, nil
}
// Create a list of type arguments for instantiating the container view type.
// Include all type arguments specified for the container type...
containerViewTypeArgs := make([]types.Type, containerViewGenericType.TypeParams().Len())
for i := range containerType.TypeArgs().Len() {
containerViewTypeArgs[i] = containerType.TypeArgs().At(i)
}
// ...and add the element view type.
// For that, we need to first determine the named elem type...
elemType, ok := baseType(containerType.TypeArgs().At(containerType.TypeArgs().Len() - 1)).(*types.Named)
if !ok {
return nil, nil
}
// ...then infer the view type from it.
var elemViewType *types.Named
elemTypeName := elemType.Obj().Name()
elemViewTypeBaseName := elemType.Obj().Name() + "View"
if elemViewTypeName, ok := elemType.Obj().Pkg().Scope().Lookup(elemViewTypeBaseName).(*types.TypeName); ok {
// The elem's view type is already defined in the same package as the elem type.
elemViewType = elemViewTypeName.Type().(*types.Named)
} else if slices.Contains(typeNames, elemTypeName) {
// The elem's view type has not been generated yet, but we can define
// and use a blank type with the expected view type name.
elemViewTypeName = types.NewTypeName(0, elemType.Obj().Pkg(), elemViewTypeBaseName, nil)
elemViewType = types.NewNamed(elemViewTypeName, types.NewStruct(nil, nil), nil)
if elemTypeParams := elemType.TypeParams(); elemTypeParams != nil {
elemViewType.SetTypeParams(collectTypeParams(elemTypeParams))
}
} else {
// The elem view type does not exist and won't be generated.
return nil, nil
}
// If elemType is an instantiated generic type, instantiate the elemViewType as well.
if elemTypeArgs := elemType.TypeArgs(); elemTypeArgs != nil {
elemViewType = must.Get(types.Instantiate(nil, elemViewType, collectTypes(elemTypeArgs), false)).(*types.Named)
}
// And finally set the elemViewType as the last type argument.
containerViewTypeArgs[len(containerViewTypeArgs)-1] = elemViewType
// Instantiate the container view type with the specified type arguments.
containerViewType := must.Get(types.Instantiate(nil, containerViewGenericType, containerViewTypeArgs, false))
// Look up a function to create a view of a container.
// It should be in the same package as the container type, named {ViewType}Of,
// and have a signature like {ViewType}Of(c *Container[T]) ContainerView[T, V].
makeContainerView, ok := containerType.Obj().Pkg().Scope().Lookup(containerViewTypeName + "Of").(*types.Func)
if !ok {
return nil, nil
}
return containerViewType.(*types.Named), makeContainerView
}
func baseType(typ types.Type) types.Type {
if ptr, ok := typ.(*types.Pointer); ok {
return ptr.Elem()
}
return typ
}
func collectTypes(list *types.TypeList) []types.Type {
// TODO(nickkhyl): use slices.Collect in Go 1.23?
if list.Len() == 0 {
return nil
}
res := make([]types.Type, list.Len())
for i := range res {
res[i] = list.At(i)
}
return res
}
func collectTypeParams(list *types.TypeParamList) []*types.TypeParam {
if list.Len() == 0 {
return nil
}
res := make([]*types.TypeParam, list.Len())
for i := range res {
p := list.At(i)
res[i] = types.NewTypeParam(p.Obj(), p.Constraint())
}
return res
}
var (
flagTypes = flag.String("type", "", "comma-separated list of types; required")
flagBuildTags = flag.String("tags", "", "compiler build tags to apply")
flagCloneFunc = flag.Bool("clonefunc", false, "add a top-level Clone func")
flagCloneOnlyTypes = flag.String("clone-only-type", "", "comma-separated list of types (a subset of --type) that should only generate a go:generate clone line and not actual views")
typeNames []string
)
func main() {
log.SetFlags(0)
log.SetPrefix("viewer: ")
flag.Parse()
if len(*flagTypes) == 0 {
flag.Usage()
os.Exit(2)
}
typeNames = strings.Split(*flagTypes, ",")
var flagArgs []string
flagArgs = append(flagArgs, fmt.Sprintf("-clonefunc=%v", *flagCloneFunc))
if *flagTypes != "" {
flagArgs = append(flagArgs, "-type="+*flagTypes)
}
if *flagBuildTags != "" {
flagArgs = append(flagArgs, "-tags="+*flagBuildTags)
}
pkg, namedTypes, err := codegen.LoadTypes(*flagBuildTags, ".")
if err != nil {
log.Fatal(err)
}
it := codegen.NewImportTracker(pkg.Types)
cloneOnlyType := map[string]bool{}
for _, t := range strings.Split(*flagCloneOnlyTypes, ",") {
cloneOnlyType[t] = true
}
buf := new(bytes.Buffer)
fmt.Fprintf(buf, "//go:generate go run tailscale.com/cmd/cloner %s\n\n", strings.Join(flagArgs, " "))
runCloner := false
for _, typeName := range typeNames {
if cloneOnlyType[typeName] {
continue
}
typ, ok := namedTypes[typeName]
if !ok {
log.Fatalf("could not find type %s", typeName)
}
var hasClone bool
for i, n := 0, typ.NumMethods(); i < n; i++ {
if typ.Method(i).Name() == "Clone" {
hasClone = true
break
}
}
if !hasClone {
runCloner = true
}
genView(buf, it, typ, pkg.Types)
}
out := pkg.Name + "_view"
if *flagBuildTags == "test" {
out += "_test"
}
out += ".go"
if err := codegen.WritePackageFile("tailscale/cmd/viewer", pkg, out, it, buf); err != nil {
log.Fatal(err)
}
if runCloner {
// When a new package is added or when existing generated files have
// been deleted, we might run into a case where tailscale.com/cmd/cloner
// has not run yet. We detect this by verifying that all the structs we
// interacted with have had Clone method already generated. If they
// haven't we ask the caller to rerun generation again so that those get
// generated.
log.Printf("%v requires regeneration. Please run go generate again", pkg.Name+"_clone.go")
}
}