tailscale/cmd/viewer/viewer.go

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// 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"}}
func(v {{.ViewName}}) {{.FieldName}}() views.Map[{{.MapKeyType}},{{.MapValueType}}] { return views.MapOf(v.ж.{{.FieldName}})}
{{end}}
{{define "mapFnField"}}
func(v {{.ViewName}}) {{.FieldName}}() views.MapFn[{{.MapKeyType}},{{.MapValueType}},{{.MapValueView}}] { return views.MapFnOf(v.ж.{{.FieldName}}, func (t {{.MapValueType}}) {{.MapValueView}} {
return {{.MapFn}}
})}
{{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
MapKeyType string
MapValueType string
MapValueView string
MapFn 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/netip.Prefix", "net/netip.Prefix":
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, *types.Named:
strucT := underlying
args.FieldType = it.QualifiedName(fieldType)
if codegen.ContainsPointers(strucT) {
writeTemplate("viewField")
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 = 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:
args.MapValueView = fmt.Sprintf("views.Slice[%v]", sElem)
args.MapValueType = "[]" + sElem.String()
args.MapFn = "views.SliceOf(t)"
template = "mapFnField"
case *types.Pointer:
ptr := x
pElem := ptr.Elem()
switch pElem.(type) {
case *types.Struct, *types.Named:
ptrType := it.QualifiedName(ptr)
viewType := 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"
}
default:
template = "unsupportedField"
}
case *types.Pointer:
ptr := u
pElem := ptr.Elem()
switch pElem.(type) {
case *types.Struct, *types.Named:
args.MapValueType = it.QualifiedName(ptr)
args.MapValueView = it.QualifiedName(pElem) + "View"
args.MapFn = "t.View()"
template = "mapFnField"
default:
template = "unsupportedField"
}
default:
template = "unsupportedField"
}
writeTemplate(template)
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")
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")
)
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.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")
}
}