cmd/viewer: add codegen tool for Views

Signed-off-by: Maisem Ali <maisem@tailscale.com>
bradfitz/dot
Maisem Ali 3 years ago committed by Maisem Ali
parent e409e59a54
commit c4e9739251

@ -125,8 +125,13 @@ func gen(buf *bytes.Buffer, it *codegen.ImportTracker, typ *types.Named) {
n := it.QualifiedName(ft.Elem())
writef("dst.%s = make([]%s, len(src.%s))", fname, n, fname)
writef("for i := range dst.%s {", fname)
if _, isPtr := ft.Elem().(*types.Pointer); isPtr {
if ptr, isPtr := ft.Elem().(*types.Pointer); isPtr {
if _, isBasic := ptr.Elem().Underlying().(*types.Basic); isBasic {
writef("\tx := *src.%s[i]", fname)
writef("\tdst.%s[i] = &x", fname)
} else {
writef("\tdst.%s[i] = src.%s[i].Clone()", fname, fname)
}
} else {
writef("\tdst.%s[i] = *src.%s[i].Clone()", fname, fname)
}

@ -0,0 +1,48 @@
// Copyright (c) 2022 Tailscale Inc & AUTHORS All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// Package tests serves a list of tests for tailscale.com/cmd/viewer.
package tests
import (
"fmt"
"inet.af/netaddr"
)
//go:generate go run tailscale.com/cmd/viewer --type=StructWithPtrs,StructWithoutPtrs,Map,StructWithSlices
type StructWithoutPtrs struct {
Int int
Pfx netaddr.IPPrefix
}
type Map struct {
M map[string]int
}
type StructWithPtrs struct {
Value *StructWithoutPtrs
Int *int
NoCloneValue *StructWithoutPtrs `codegen:"noclone"`
}
func (v *StructWithPtrs) String() string { return fmt.Sprintf("%v", v.Int) }
func (v *StructWithPtrs) Equal(v2 *StructWithPtrs) bool {
return v.Value == v2.Value
}
type StructWithSlices struct {
Values []StructWithoutPtrs
ValuePointers []*StructWithoutPtrs
StructPointers []*StructWithPtrs
Structs []StructWithPtrs
Ints []*int
Slice []string
Prefixes []netaddr.IPPrefix
Data []byte
}

@ -0,0 +1,120 @@
// Copyright (c) 2022 Tailscale Inc & AUTHORS All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// Code generated by tailscale.com/cmd/cloner; DO NOT EDIT.
package tests
import (
"inet.af/netaddr"
)
// Clone makes a deep copy of StructWithPtrs.
// The result aliases no memory with the original.
func (src *StructWithPtrs) Clone() *StructWithPtrs {
if src == nil {
return nil
}
dst := new(StructWithPtrs)
*dst = *src
if dst.Value != nil {
dst.Value = new(StructWithoutPtrs)
*dst.Value = *src.Value
}
if dst.Int != nil {
dst.Int = new(int)
*dst.Int = *src.Int
}
return dst
}
// A compilation failure here means this code must be regenerated, with the command at the top of this file.
var _StructWithPtrsCloneNeedsRegeneration = StructWithPtrs(struct {
Value *StructWithoutPtrs
Int *int
NoCloneValue *StructWithoutPtrs
}{})
// Clone makes a deep copy of StructWithoutPtrs.
// The result aliases no memory with the original.
func (src *StructWithoutPtrs) Clone() *StructWithoutPtrs {
if src == nil {
return nil
}
dst := new(StructWithoutPtrs)
*dst = *src
return dst
}
// A compilation failure here means this code must be regenerated, with the command at the top of this file.
var _StructWithoutPtrsCloneNeedsRegeneration = StructWithoutPtrs(struct {
Int int
Pfx netaddr.IPPrefix
}{})
// Clone makes a deep copy of Map.
// The result aliases no memory with the original.
func (src *Map) Clone() *Map {
if src == nil {
return nil
}
dst := new(Map)
*dst = *src
if dst.M != nil {
dst.M = map[string]int{}
for k, v := range src.M {
dst.M[k] = v
}
}
return dst
}
// A compilation failure here means this code must be regenerated, with the command at the top of this file.
var _MapCloneNeedsRegeneration = Map(struct {
M map[string]int
}{})
// Clone makes a deep copy of StructWithSlices.
// The result aliases no memory with the original.
func (src *StructWithSlices) Clone() *StructWithSlices {
if src == nil {
return nil
}
dst := new(StructWithSlices)
*dst = *src
dst.Values = append(src.Values[:0:0], src.Values...)
dst.ValuePointers = make([]*StructWithoutPtrs, len(src.ValuePointers))
for i := range dst.ValuePointers {
dst.ValuePointers[i] = src.ValuePointers[i].Clone()
}
dst.StructPointers = make([]*StructWithPtrs, len(src.StructPointers))
for i := range dst.StructPointers {
dst.StructPointers[i] = src.StructPointers[i].Clone()
}
dst.Structs = make([]StructWithPtrs, len(src.Structs))
for i := range dst.Structs {
dst.Structs[i] = *src.Structs[i].Clone()
}
dst.Ints = make([]*int, len(src.Ints))
for i := range dst.Ints {
x := *src.Ints[i]
dst.Ints[i] = &x
}
dst.Slice = append(src.Slice[:0:0], src.Slice...)
dst.Prefixes = append(src.Prefixes[:0:0], src.Prefixes...)
dst.Data = append(src.Data[:0:0], src.Data...)
return dst
}
// A compilation failure here means this code must be regenerated, with the command at the top of this file.
var _StructWithSlicesCloneNeedsRegeneration = StructWithSlices(struct {
Values []StructWithoutPtrs
ValuePointers []*StructWithoutPtrs
StructPointers []*StructWithPtrs
Structs []StructWithPtrs
Ints []*int
Slice []string
Prefixes []netaddr.IPPrefix
Data []byte
}{})

@ -0,0 +1,268 @@
// Copyright (c) 2022 Tailscale Inc & AUTHORS All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// Code generated by tailscale/cmd/viewer; DO NOT EDIT.
package tests
import (
"encoding/json"
"errors"
"go4.org/mem"
"inet.af/netaddr"
"tailscale.com/types/views"
)
//go:generate go run tailscale.com/cmd/cloner -clonefunc=false -type=StructWithPtrs,StructWithoutPtrs,Map,StructWithSlices
// View returns a readonly view of StructWithPtrs.
func (p *StructWithPtrs) View() StructWithPtrsView {
return StructWithPtrsView{ж: p}
}
// StructWithPtrsView provides a read-only view over StructWithPtrs.
//
// Its methods should only be called if `Valid()` returns true.
type StructWithPtrsView 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 *StructWithPtrs
}
// Valid reports whether underlying value is non-nil.
func (v StructWithPtrsView) Valid() bool { return v.ж != nil }
// AsStruct returns a clone of the underlying value which aliases no memory with
// the original.
func (v StructWithPtrsView) AsStruct() *StructWithPtrs {
if v.ж == nil {
return nil
}
return v.ж.Clone()
}
func (v StructWithPtrsView) MarshalJSON() ([]byte, error) { return json.Marshal(v.ж) }
func (v *StructWithPtrsView) UnmarshalJSON(b []byte) error {
if v.ж != nil {
return errors.New("already initialized")
}
if len(b) == 0 {
return nil
}
var x StructWithPtrs
if err := json.Unmarshal(b, &x); err != nil {
return err
}
v.ж = &x
return nil
}
func (v StructWithPtrsView) Value() *StructWithoutPtrs {
if v.ж.Value == nil {
return nil
}
x := *v.ж.Value
return &x
}
func (v StructWithPtrsView) Int() *int {
if v.ж.Int == nil {
return nil
}
x := *v.ж.Int
return &x
}
func (v StructWithPtrsView) NoCloneValue() *StructWithoutPtrs { return v.ж.NoCloneValue }
func (v StructWithPtrsView) String() string { return v.ж.String() }
func (v StructWithPtrsView) Equal(v2 StructWithPtrsView) bool { return v.ж.Equal(v2.ж) }
// A compilation failure here means this code must be regenerated, with the command at the top of this file.
var _StructWithPtrsViewNeedsRegeneration = StructWithPtrs(struct {
Value *StructWithoutPtrs
Int *int
NoCloneValue *StructWithoutPtrs
}{})
// View returns a readonly view of StructWithoutPtrs.
func (p *StructWithoutPtrs) View() StructWithoutPtrsView {
return StructWithoutPtrsView{ж: p}
}
// StructWithoutPtrsView provides a read-only view over StructWithoutPtrs.
//
// Its methods should only be called if `Valid()` returns true.
type StructWithoutPtrsView 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 *StructWithoutPtrs
}
// Valid reports whether underlying value is non-nil.
func (v StructWithoutPtrsView) Valid() bool { return v.ж != nil }
// AsStruct returns a clone of the underlying value which aliases no memory with
// the original.
func (v StructWithoutPtrsView) AsStruct() *StructWithoutPtrs {
if v.ж == nil {
return nil
}
return v.ж.Clone()
}
func (v StructWithoutPtrsView) MarshalJSON() ([]byte, error) { return json.Marshal(v.ж) }
func (v *StructWithoutPtrsView) UnmarshalJSON(b []byte) error {
if v.ж != nil {
return errors.New("already initialized")
}
if len(b) == 0 {
return nil
}
var x StructWithoutPtrs
if err := json.Unmarshal(b, &x); err != nil {
return err
}
v.ж = &x
return nil
}
func (v StructWithoutPtrsView) Int() int { return v.ж.Int }
func (v StructWithoutPtrsView) Pfx() netaddr.IPPrefix { return v.ж.Pfx }
// A compilation failure here means this code must be regenerated, with the command at the top of this file.
var _StructWithoutPtrsViewNeedsRegeneration = StructWithoutPtrs(struct {
Int int
Pfx netaddr.IPPrefix
}{})
// View returns a readonly view of Map.
func (p *Map) View() MapView {
return MapView{ж: p}
}
// MapView provides a read-only view over Map.
//
// Its methods should only be called if `Valid()` returns true.
type MapView 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 *Map
}
// Valid reports whether underlying value is non-nil.
func (v MapView) Valid() bool { return v.ж != nil }
// AsStruct returns a clone of the underlying value which aliases no memory with
// the original.
func (v MapView) AsStruct() *Map {
if v.ж == nil {
return nil
}
return v.ж.Clone()
}
func (v MapView) MarshalJSON() ([]byte, error) { return json.Marshal(v.ж) }
func (v *MapView) UnmarshalJSON(b []byte) error {
if v.ж != nil {
return errors.New("already initialized")
}
if len(b) == 0 {
return nil
}
var x Map
if err := json.Unmarshal(b, &x); err != nil {
return err
}
v.ж = &x
return nil
}
// A compilation failure here means this code must be regenerated, with the command at the top of this file.
var _MapViewNeedsRegeneration = Map(struct {
M map[string]int
}{})
// View returns a readonly view of StructWithSlices.
func (p *StructWithSlices) View() StructWithSlicesView {
return StructWithSlicesView{ж: p}
}
// StructWithSlicesView provides a read-only view over StructWithSlices.
//
// Its methods should only be called if `Valid()` returns true.
type StructWithSlicesView 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 *StructWithSlices
}
// Valid reports whether underlying value is non-nil.
func (v StructWithSlicesView) Valid() bool { return v.ж != nil }
// AsStruct returns a clone of the underlying value which aliases no memory with
// the original.
func (v StructWithSlicesView) AsStruct() *StructWithSlices {
if v.ж == nil {
return nil
}
return v.ж.Clone()
}
func (v StructWithSlicesView) MarshalJSON() ([]byte, error) { return json.Marshal(v.ж) }
func (v *StructWithSlicesView) UnmarshalJSON(b []byte) error {
if v.ж != nil {
return errors.New("already initialized")
}
if len(b) == 0 {
return nil
}
var x StructWithSlices
if err := json.Unmarshal(b, &x); err != nil {
return err
}
v.ж = &x
return nil
}
func (v StructWithSlicesView) Values() views.Slice[StructWithoutPtrs] {
return views.SliceOf(v.ж.Values)
}
func (v StructWithSlicesView) ValuePointers() views.SliceView[*StructWithoutPtrs, StructWithoutPtrsView] {
return views.SliceOfViews[*StructWithoutPtrs, StructWithoutPtrsView](v.ж.ValuePointers)
}
func (v StructWithSlicesView) StructPointers() views.SliceView[*StructWithPtrs, StructWithPtrsView] {
return views.SliceOfViews[*StructWithPtrs, StructWithPtrsView](v.ж.StructPointers)
}
func (v StructWithSlicesView) Structs() StructWithPtrs { panic("unsupported") }
func (v StructWithSlicesView) Ints() *int { panic("unsupported") }
func (v StructWithSlicesView) Slice() views.Slice[string] { return views.SliceOf(v.ж.Slice) }
func (v StructWithSlicesView) Prefixes() views.IPPrefixSlice {
return views.IPPrefixSliceOf(v.ж.Prefixes)
}
func (v StructWithSlicesView) Data() mem.RO { return mem.B(v.ж.Data) }
// A compilation failure here means this code must be regenerated, with the command at the top of this file.
var _StructWithSlicesViewNeedsRegeneration = StructWithSlices(struct {
Values []StructWithoutPtrs
ValuePointers []*StructWithoutPtrs
StructPointers []*StructWithPtrs
Structs []StructWithPtrs
Ints []*int
Slice []string
Prefixes []netaddr.IPPrefix
Data []byte
}{})

@ -0,0 +1,316 @@
// Copyright (c) 2022 Tailscale Inc & AUTHORS All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// 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"
"strings"
"tailscale.com/util/codegen"
)
const viewTemplateStr = `{{define "common"}}
// View returns a readonly view of {{.StructName}}.
func (p *{{.StructName}}) View() {{.ViewName}} {
return {{.ViewName}}{ж: p}
}
// {{.ViewName}} provides a read-only view over {{.StructName}}.
//
// Its methods should only be called if ` + "`Valid()`" + ` returns true.
type {{.ViewName}} 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}}
}
// Valid reports whether underlying value is non-nil.
func (v {{.ViewName}}) Valid() bool { return v.ж != nil }
// AsStruct returns a clone of the underlying value which aliases no memory with
// the original.
func (v {{.ViewName}}) AsStruct() *{{.StructName}}{
if v.ж == nil {
return nil
}
return v.ж.Clone()
}
func (v {{.ViewName}}) MarshalJSON() ([]byte, error) { return json.Marshal(v.ж) }
func (v *{{.ViewName}}) UnmarshalJSON(b []byte) error {
if v.ж != nil {
return errors.New("already initialized")
}
if len(b) == 0 {
return nil
}
var x {{.StructName}}
if err := json.Unmarshal(b, &x); err != nil {
return err
}
v.ж=&x
return nil
}
{{end}}
{{define "valueField"}}func (v {{.ViewName}}) {{.FieldName}}() {{.FieldType}} { return v.ж.{{.FieldName}} }
{{end}}
{{define "byteSliceField"}}func (v {{.ViewName}}) {{.FieldName}}() mem.RO { return mem.B(v.ж.{{.FieldName}}) }
{{end}}
{{define "ipPrefixSliceField"}}func (v {{.ViewName}}) {{.FieldName}}() views.IPPrefixSlice { return views.IPPrefixSliceOf(v.ж.{{.FieldName}}) }
{{end}}
{{define "sliceField"}}func (v {{.ViewName}}) {{.FieldName}}() views.Slice[{{.FieldType}}] { return views.SliceOf(v.ж.{{.FieldName}}) }
{{end}}
{{define "viewSliceField"}}func (v {{.ViewName}}) {{.FieldName}}() views.SliceView[{{.FieldType}},{{.FieldViewName}}] { return views.SliceOfViews[{{.FieldType}},{{.FieldViewName}}](v.ж.{{.FieldName}}) }
{{end}}
{{define "viewField"}}func (v {{.ViewName}}) {{.FieldName}}() {{.FieldType}}View { return v.ж.{{.FieldName}}.View() }
{{end}}
{{define "valuePointerField"}}func (v {{.ViewName}}) {{.FieldName}}() {{.FieldType}} {
if v.ж.{{.FieldName}} == nil {
return nil
}
x := *v.ж.{{.FieldName}}
return &x
}
{{end}}
{{define "mapField"}}
// Unsupported, panics.
func(v {{.ViewName}}) {{.FieldName}}() {{.FieldType}} {panic("unsupported")}
{{end}}
{{define "unsupportedField"}}func(v {{.ViewName}}) {{.FieldName}}() {{.FieldType}} {panic("unsupported")}
{{end}}
{{define "stringFunc"}}func(v {{.ViewName}}) String() string { return v.ж.String() }
{{end}}
{{define "equalFunc"}}func(v {{.ViewName}}) Equal(v2 {{.ViewName}}) 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
FieldName string
FieldType string
FieldViewName string
}{
StructName: typ.Obj().Name(),
ViewName: typ.Obj().Name() + "View",
}
writeTemplate := func(name string) {
if err := viewTemplate.ExecuteTemplate(buf, name, args); err != nil {
log.Fatal(err)
}
}
writeTemplate("common")
for i := 0; i < t.NumFields(); i++ {
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()
args.FieldType = it.QualifiedName(elem)
switch elem.String() {
case "byte":
it.Import("go4.org/mem")
writeTemplate("byteSliceField")
case "inet.af/netaddr.IPPrefix":
it.Import("tailscale.com/types/views")
writeTemplate("ipPrefixSliceField")
default:
it.Import("tailscale.com/types/views")
shallow, deep, base := requiresCloning(elem)
if deep {
if _, isPtr := elem.(*types.Pointer); isPtr {
args.FieldViewName = it.QualifiedName(base) + "View"
writeTemplate("viewSliceField")
} else {
writeTemplate("unsupportedField")
}
continue
} else if shallow {
if _, isBasic := base.(*types.Basic); isBasic {
writeTemplate("unsupportedField")
} else {
args.FieldViewName = it.QualifiedName(base) + "View"
writeTemplate("viewSliceField")
}
continue
}
writeTemplate("sliceField")
}
continue
case *types.Struct:
strucT := underlying
args.FieldType = it.QualifiedName(fieldType)
if codegen.ContainsPointers(strucT) {
writeTemplate("viewField")
continue
}
writeTemplate("valueField")
continue
case *types.Map:
// TODO(maisem): support this.
// args.FieldType = importedName(ft)
// writeTemplate("mapField")
continue
case *types.Pointer:
ptr := underlying
_, deep, base := requiresCloning(ptr)
if deep {
args.FieldType = it.QualifiedName(base)
writeTemplate("viewField")
} else {
args.FieldType = it.QualifiedName(ptr)
writeTemplate("valuePointerField")
}
continue
}
writeTemplate("unsupportedField")
}
for i := 0; i < typ.NumMethods(); i++ {
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, "View", it))
}
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")
)
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)
buf := new(bytes.Buffer)
fmt.Fprintf(buf, `//go:generate go run tailscale.com/cmd/cloner %s`, strings.Join(flagArgs, " "))
fmt.Fprintln(buf)
runCloner := false
for _, typeName := range typeNames {
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.go"
if err := codegen.WritePackageFile("tailscale/cmd/viewer", pkg, out, it, buf); err != nil {
log.Fatal(err)
}
if runCloner {
// When a new pacakge 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")
}
}

@ -14,6 +14,78 @@ import (
"tailscale.com/net/tsaddr"
)
func unmarshalJSON[T any](b []byte, x *[]T) error {
if *x != nil {
return errors.New("already initialized")
}
if len(b) == 0 {
return nil
}
return json.Unmarshal(b, x)
}
// StructView represents the corresponding StructView of a Viewable. The concrete types are
// typically generated by tailscale.com/cmd/viewer.
type StructView[T any] interface {
// Valid reports whether the underlying Viewable is nil.
Valid() bool
// AsStruct returns a deep-copy of the underlying value.
// It returns nil, if Valid() is false.
AsStruct() T
}
// ViewCloner is any type that has had View and Clone funcs generated using
// tailscale.com/cmd/viewer.
type ViewCloner[T any, V StructView[T]] interface {
// View returns a read-only view of Viewable.
// If Viewable is nil, View().Valid() reports false.
View() V
// Clone returns a deep-clone of Viewable.
// It returns nil, when Viewable is nil.
Clone() T
}
// SliceOfViews returns a ViewSlice for x.
func SliceOfViews[T ViewCloner[T, V], V StructView[T]](x []T) SliceView[T, V] {
return SliceView[T, V]{x}
}
// SliceView is a read-only wrapper around a struct which should only be exposed
// as a View.
type SliceView[T ViewCloner[T, V], V StructView[T]] struct {
// 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 []T
}
// MarshalJSON implements json.Marshaler.
func (v SliceView[T, V]) MarshalJSON() ([]byte, error) { return json.Marshal(v.ж) }
// UnmarshalJSON implements json.Unmarshaler.
func (v *SliceView[T, V]) UnmarshalJSON(b []byte) error { return unmarshalJSON(b, &v.ж) }
// IsNil reports whether the underlying slice is nil.
func (v SliceView[T, V]) IsNil() bool { return v.ж == nil }
// Len returns the length of the slice.
func (v SliceView[T, V]) Len() int { return len(v.ж) }
// At returns a View of the element at index `i` of the slice.
func (v SliceView[T, V]) At(i int) V { return v.ж[i].View() }
// AppendTo appends the underlying slice values to dst.
func (v SliceView[T, V]) AppendTo(dst []V) []V {
for _, x := range v.ж {
dst = append(dst, x.View())
}
return dst
}
// AsSlice returns a copy of underlying slice.
func (v SliceView[T, V]) AsSlice() []V {
return v.AppendTo(nil)
}
// Slice is a read-only accessor for a slice.
type Slice[T any] struct {
// It is named distinctively to make you think of how dangerous it is to escape
@ -31,16 +103,7 @@ func (v Slice[T]) MarshalJSON() ([]byte, error) {
// UnmarshalJSON implements json.Unmarshaler.
func (v *Slice[T]) UnmarshalJSON(b []byte) error {
if v.ж != nil {
return errors.New("Slice is already initialized")
}
if len(b) == 0 {
return nil
}
if err := json.Unmarshal(b, &v.ж); err != nil {
return err
}
return nil
return unmarshalJSON(b, &v.ж)
}
// IsNil reports whether the underlying slice is nil.

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