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// Copyright 2020 The Go 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 protorange provides functionality to traverse a message value.
package protorange
import (
"bytes"
"errors"
"google.golang.org/protobuf/internal/genid"
"google.golang.org/protobuf/internal/order"
"google.golang.org/protobuf/proto"
"google.golang.org/protobuf/reflect/protopath"
"google.golang.org/protobuf/reflect/protoreflect"
"google.golang.org/protobuf/reflect/protoregistry"
)
var (
// Break breaks traversal of children in the current value.
// It has no effect when traversing values that are not composite types
// (e.g., messages, lists, and maps).
Break = errors.New("break traversal of children in current value")
// Terminate terminates the entire range operation.
// All necessary Pop operations continue to be called.
Terminate = errors.New("terminate range operation")
)
// Range performs a depth-first traversal over reachable values in a message.
//
// See Options.Range for details.
func Range(m protoreflect.Message, f func(protopath.Values) error) error {
return Options{}.Range(m, f, nil)
}
// Options configures traversal of a message value tree.
type Options struct {
// Stable specifies whether to visit message fields and map entries
// in a stable ordering. If false, then the ordering is undefined and
// may be non-deterministic.
//
// Message fields are visited in ascending order by field number.
// Map entries are visited in ascending order, where
// boolean keys are ordered such that false sorts before true,
// numeric keys are ordered based on the numeric value, and
// string keys are lexicographically ordered by Unicode codepoints.
Stable bool
// Resolver is used for looking up types when expanding google.protobuf.Any
// messages. If nil, this defaults to using protoregistry.GlobalTypes.
// To prevent expansion of Any messages, pass an empty protoregistry.Types:
//
// Options{Resolver: (*protoregistry.Types)(nil)}
//
Resolver interface {
protoregistry.ExtensionTypeResolver
protoregistry.MessageTypeResolver
}
}
// Range performs a depth-first traversal over reachable values in a message.
// The first push and the last pop are to push/pop a protopath.Root step.
// If push or pop return any non-nil error (other than Break or Terminate),
// it terminates the traversal and is returned by Range.
//
// The rules for traversing a message is as follows:
//
// • For messages, iterate over every populated known and extension field.
// Each field is preceded by a push of a protopath.FieldAccess step,
// followed by recursive application of the rules on the field value,
// and succeeded by a pop of that step.
// If the message has unknown fields, then push an protopath.UnknownAccess step
// followed immediately by pop of that step.
//
// • As an exception to the above rule, if the current message is a
// google.protobuf.Any message, expand the underlying message (if resolvable).
// The expanded message is preceded by a push of a protopath.AnyExpand step,
// followed by recursive application of the rules on the underlying message,
// and succeeded by a pop of that step. Mutations to the expanded message
// are written back to the Any message when popping back out.
//
// • For lists, iterate over every element. Each element is preceded by a push
// of a protopath.ListIndex step, followed by recursive application of the rules
// on the list element, and succeeded by a pop of that step.
//
// • For maps, iterate over every entry. Each entry is preceded by a push
// of a protopath.MapIndex step, followed by recursive application of the rules
// on the map entry value, and succeeded by a pop of that step.
//
// Mutations should only be made to the last value, otherwise the effects on
// traversal will be undefined. If the mutation is made to the last value
// during to a push, then the effects of the mutation will affect traversal.
// For example, if the last value is currently a message, and the push function
// populates a few fields in that message, then the newly modified fields
// will be traversed.
//
// The protopath.Values provided to push functions is only valid until the
// corresponding pop call and the values provided to a pop call is only valid
// for the duration of the pop call itself.
func (o Options) Range(m protoreflect.Message, push, pop func(protopath.Values) error) error {
var err error
p := new(protopath.Values)
if o.Resolver == nil {
o.Resolver = protoregistry.GlobalTypes
}
pushStep(p, protopath.Root(m.Descriptor()), protoreflect.ValueOfMessage(m))
if push != nil {
err = amendError(err, push(*p))
}
if err == nil {
err = o.rangeMessage(p, m, push, pop)
}
if pop != nil {
err = amendError(err, pop(*p))
}
popStep(p)
if err == Break || err == Terminate {
err = nil
}
return err
}
func (o Options) rangeMessage(p *protopath.Values, m protoreflect.Message, push, pop func(protopath.Values) error) (err error) {
if ok, err := o.rangeAnyMessage(p, m, push, pop); ok {
return err
}
fieldOrder := order.AnyFieldOrder
if o.Stable {
fieldOrder = order.NumberFieldOrder
}
order.RangeFields(m, fieldOrder, func(fd protoreflect.FieldDescriptor, v protoreflect.Value) bool {
pushStep(p, protopath.FieldAccess(fd), v)
if push != nil {
err = amendError(err, push(*p))
}
if err == nil {
switch {
case fd.IsMap():
err = o.rangeMap(p, fd, v.Map(), push, pop)
case fd.IsList():
err = o.rangeList(p, fd, v.List(), push, pop)
case fd.Message() != nil:
err = o.rangeMessage(p, v.Message(), push, pop)
}
}
if pop != nil {
err = amendError(err, pop(*p))
}
popStep(p)
return err == nil
})
if b := m.GetUnknown(); len(b) > 0 && err == nil {
pushStep(p, protopath.UnknownAccess(), protoreflect.ValueOfBytes(b))
if push != nil {
err = amendError(err, push(*p))
}
if pop != nil {
err = amendError(err, pop(*p))
}
popStep(p)
}
if err == Break {
err = nil
}
return err
}
func (o Options) rangeAnyMessage(p *protopath.Values, m protoreflect.Message, push, pop func(protopath.Values) error) (ok bool, err error) {
md := m.Descriptor()
if md.FullName() != "google.protobuf.Any" {
return false, nil
}
fds := md.Fields()
url := m.Get(fds.ByNumber(genid.Any_TypeUrl_field_number)).String()
val := m.Get(fds.ByNumber(genid.Any_Value_field_number)).Bytes()
mt, errFind := o.Resolver.FindMessageByURL(url)
if errFind != nil {
return false, nil
}
// Unmarshal the raw encoded message value into a structured message value.
m2 := mt.New()
errUnmarshal := proto.UnmarshalOptions{
Merge: true,
AllowPartial: true,
Resolver: o.Resolver,
}.Unmarshal(val, m2.Interface())
if errUnmarshal != nil {
// If the the underlying message cannot be unmarshaled,
// then just treat this as an normal message type.
return false, nil
}
// Marshal Any before ranging to detect possible mutations.
b1, errMarshal := proto.MarshalOptions{
AllowPartial: true,
Deterministic: true,
}.Marshal(m2.Interface())
if errMarshal != nil {
return true, errMarshal
}
pushStep(p, protopath.AnyExpand(m2.Descriptor()), protoreflect.ValueOfMessage(m2))
if push != nil {
err = amendError(err, push(*p))
}
if err == nil {
err = o.rangeMessage(p, m2, push, pop)
}
if pop != nil {
err = amendError(err, pop(*p))
}
popStep(p)
// Marshal Any after ranging to detect possible mutations.
b2, errMarshal := proto.MarshalOptions{
AllowPartial: true,
Deterministic: true,
}.Marshal(m2.Interface())
if errMarshal != nil {
return true, errMarshal
}
// Mutations detected, write the new sequence of bytes to the Any message.
if !bytes.Equal(b1, b2) {
m.Set(fds.ByNumber(genid.Any_Value_field_number), protoreflect.ValueOfBytes(b2))
}
if err == Break {
err = nil
}
return true, err
}
func (o Options) rangeList(p *protopath.Values, fd protoreflect.FieldDescriptor, ls protoreflect.List, push, pop func(protopath.Values) error) (err error) {
for i := 0; i < ls.Len() && err == nil; i++ {
v := ls.Get(i)
pushStep(p, protopath.ListIndex(i), v)
if push != nil {
err = amendError(err, push(*p))
}
if err == nil && fd.Message() != nil {
err = o.rangeMessage(p, v.Message(), push, pop)
}
if pop != nil {
err = amendError(err, pop(*p))
}
popStep(p)
}
if err == Break {
err = nil
}
return err
}
func (o Options) rangeMap(p *protopath.Values, fd protoreflect.FieldDescriptor, ms protoreflect.Map, push, pop func(protopath.Values) error) (err error) {
keyOrder := order.AnyKeyOrder
if o.Stable {
keyOrder = order.GenericKeyOrder
}
order.RangeEntries(ms, keyOrder, func(k protoreflect.MapKey, v protoreflect.Value) bool {
pushStep(p, protopath.MapIndex(k), v)
if push != nil {
err = amendError(err, push(*p))
}
if err == nil && fd.MapValue().Message() != nil {
err = o.rangeMessage(p, v.Message(), push, pop)
}
if pop != nil {
err = amendError(err, pop(*p))
}
popStep(p)
return err == nil
})
if err == Break {
err = nil
}
return err
}
func pushStep(p *protopath.Values, s protopath.Step, v protoreflect.Value) {
p.Path = append(p.Path, s)
p.Values = append(p.Values, v)
}
func popStep(p *protopath.Values) {
p.Path = p.Path[:len(p.Path)-1]
p.Values = p.Values[:len(p.Values)-1]
}
// amendErrors amends the previous error with the current error if it is
// considered more serious. The precedence order for errors is:
// nil < Break < Terminate < previous non-nil < current non-nil
func amendError(prev, curr error) error {
switch {
case curr == nil:
return prev
case curr == Break && prev != nil:
return prev
case curr == Terminate && prev != nil && prev != Break:
return prev
default:
return curr
}
}