Source: decode.go in package google.golang.org/protobuf/encoding/protojson


package protojson

import (
	"encoding/base64"
	"fmt"
	"math"
	"strconv"
	"strings"

	"google.golang.org/protobuf/internal/encoding/json"
	"google.golang.org/protobuf/internal/encoding/messageset"
	"google.golang.org/protobuf/internal/errors"
	"google.golang.org/protobuf/internal/flags"
	"google.golang.org/protobuf/internal/genid"
	"google.golang.org/protobuf/internal/pragma"
	"google.golang.org/protobuf/internal/set"
	"google.golang.org/protobuf/proto"
	pref "google.golang.org/protobuf/reflect/protoreflect"
	"google.golang.org/protobuf/reflect/protoregistry"
)

Unmarshal reads the given []byte into the given proto.Message.

func Unmarshal(b []byte, m proto.Message) error {
	return UnmarshalOptions{}.Unmarshal(b, m)
}

UnmarshalOptions is a configurable JSON format parser.

type UnmarshalOptions struct {
	pragma.NoUnkeyedLiterals

If AllowPartial is set, input for messages that will result in missing required fields will not return an error.

	AllowPartial bool

If DiscardUnknown is set, unknown fields are ignored.

	DiscardUnknown bool

Resolver is used for looking up types when unmarshaling google.protobuf.Any messages or extension fields. If nil, this defaults to using protoregistry.GlobalTypes.

	Resolver interface {
		protoregistry.MessageTypeResolver
		protoregistry.ExtensionTypeResolver
	}
}

Unmarshal reads the given []byte and populates the given proto.Message using options in UnmarshalOptions object. It will clear the message first before setting the fields. If it returns an error, the given message may be partially set.

func (o UnmarshalOptions) Unmarshal(b []byte, m proto.Message) error {
	return o.unmarshal(b, m)
}

unmarshal is a centralized function that all unmarshal operations go through. For profiling purposes, avoid changing the name of this function or introducing other code paths for unmarshal that do not go through this.

func (o UnmarshalOptions) unmarshal(b []byte, m proto.Message) error {
	proto.Reset(m)

	if o.Resolver == nil {
		o.Resolver = protoregistry.GlobalTypes
	}

	dec := decoder{json.NewDecoder(b), o}
	if err := dec.unmarshalMessage(m.ProtoReflect(), false); err != nil {
		return err
	}

Check for EOF.

	tok, err := dec.Read()
	if err != nil {
		return err
	}
	if tok.Kind() != json.EOF {
		return dec.unexpectedTokenError(tok)
	}

	if o.AllowPartial {
		return nil
	}
	return proto.CheckInitialized(m)
}

type decoder struct {
	*json.Decoder
	opts UnmarshalOptions
}

newError returns an error object with position info.

func (d decoder) newError(pos int, f string, x ...interface{}) error {
	line, column := d.Position(pos)
	head := fmt.Sprintf("(line %d:%d): ", line, column)
	return errors.New(head+f, x...)
}

unexpectedTokenError returns a syntax error for the given unexpected token.

func (d decoder) unexpectedTokenError(tok json.Token) error {
	return d.syntaxError(tok.Pos(), "unexpected token %s", tok.RawString())
}

syntaxError returns a syntax error for given position.

func (d decoder) syntaxError(pos int, f string, x ...interface{}) error {
	line, column := d.Position(pos)
	head := fmt.Sprintf("syntax error (line %d:%d): ", line, column)
	return errors.New(head+f, x...)
}

unmarshalMessage unmarshals a message into the given protoreflect.Message.

func (d decoder) unmarshalMessage(m pref.Message, skipTypeURL bool) error {
	if unmarshal := wellKnownTypeUnmarshaler(m.Descriptor().FullName()); unmarshal != nil {
		return unmarshal(d, m)
	}

	tok, err := d.Read()
	if err != nil {
		return err
	}
	if tok.Kind() != json.ObjectOpen {
		return d.unexpectedTokenError(tok)
	}

	if err := d.unmarshalFields(m, skipTypeURL); err != nil {
		return err
	}

	return nil
}

unmarshalFields unmarshals the fields into the given protoreflect.Message.

func (d decoder) unmarshalFields(m pref.Message, skipTypeURL bool) error {
	messageDesc := m.Descriptor()
	if !flags.ProtoLegacy && messageset.IsMessageSet(messageDesc) {
		return errors.New("no support for proto1 MessageSets")
	}

	var seenNums set.Ints
	var seenOneofs set.Ints
	fieldDescs := messageDesc.Fields()

Read field name.

		tok, err := d.Read()
		if err != nil {
			return err
		}
		switch tok.Kind() {
		default:
			return d.unexpectedTokenError(tok)
		case json.ObjectClose:
			return nil

Continue below.

Unmarshaling a non-custom embedded message in Any will contain the JSON field "@type" which should be skipped because it is not a field of the embedded message, but simply an artifact of the Any format.

		if skipTypeURL && name == "@type" {
			d.Read()
			continue
		}

Get the FieldDescriptor.

		var fd pref.FieldDescriptor

Only extension names are in [name] format.

			extName := pref.FullName(name[1 : len(name)-1])
			extType, err := d.findExtension(extName)
			if err != nil && err != protoregistry.NotFound {
				return d.newError(tok.Pos(), "unable to resolve %s: %v", tok.RawString(), err)
			}
			if extType != nil {
				fd = extType.TypeDescriptor()
				if !messageDesc.ExtensionRanges().Has(fd.Number()) || fd.ContainingMessage().FullName() != messageDesc.FullName() {
					return d.newError(tok.Pos(), "message %v cannot be extended by %v", messageDesc.FullName(), fd.FullName())
				}
			}

The name can either be the JSON name or the proto field name.

			fd = fieldDescs.ByJSONName(name)
			if fd == nil {
				fd = fieldDescs.ByName(pref.Name(name))

The proto name of a group field is in all lowercase, while the textual field name is the group message name.

					gd := fieldDescs.ByName(pref.Name(strings.ToLower(name)))
					if gd != nil && gd.Kind() == pref.GroupKind && gd.Message().Name() == pref.Name(name) {
						fd = gd
					}
				} else if fd.Kind() == pref.GroupKind && fd.Message().Name() != pref.Name(name) {
					fd = nil // reset since field name is actually the message name
				}
			}
		}
		if flags.ProtoLegacy {
			if fd != nil && fd.IsWeak() && fd.Message().IsPlaceholder() {
				fd = nil // reset since the weak reference is not linked in
			}
		}

Field is unknown.

			if d.opts.DiscardUnknown {
				if err := d.skipJSONValue(); err != nil {
					return err
				}
				continue
			}
			return d.newError(tok.Pos(), "unknown field %v", tok.RawString())
		}

Do not allow duplicate fields.

		num := uint64(fd.Number())
		if seenNums.Has(num) {
			return d.newError(tok.Pos(), "duplicate field %v", tok.RawString())
		}
		seenNums.Set(num)

No need to set values for JSON null unless the field type is google.protobuf.Value or google.protobuf.NullValue.

		if tok, _ := d.Peek(); tok.Kind() == json.Null && !isKnownValue(fd) && !isNullValue(fd) {
			d.Read()
			continue
		}

		switch {
		case fd.IsList():
			list := m.Mutable(fd).List()
			if err := d.unmarshalList(list, fd); err != nil {
				return err
			}
		case fd.IsMap():
			mmap := m.Mutable(fd).Map()
			if err := d.unmarshalMap(mmap, fd); err != nil {
				return err
			}

If field is a oneof, check if it has already been set.

			if od := fd.ContainingOneof(); od != nil {
				idx := uint64(od.Index())
				if seenOneofs.Has(idx) {
					return d.newError(tok.Pos(), "error parsing %s, oneof %v is already set", tok.RawString(), od.FullName())
				}
				seenOneofs.Set(idx)
			}

Required or optional fields.

			if err := d.unmarshalSingular(m, fd); err != nil {
				return err
			}
		}
	}
}

findExtension returns protoreflect.ExtensionType from the resolver if found.

func (d decoder) findExtension(xtName pref.FullName) (pref.ExtensionType, error) {
	xt, err := d.opts.Resolver.FindExtensionByName(xtName)
	if err == nil {
		return xt, nil
	}
	return messageset.FindMessageSetExtension(d.opts.Resolver, xtName)
}

func isKnownValue(fd pref.FieldDescriptor) bool {
	md := fd.Message()
	return md != nil && md.FullName() == genid.Value_message_fullname
}

func isNullValue(fd pref.FieldDescriptor) bool {
	ed := fd.Enum()
	return ed != nil && ed.FullName() == genid.NullValue_enum_fullname
}

unmarshalSingular unmarshals to the non-repeated field specified by the given FieldDescriptor.

func (d decoder) unmarshalSingular(m pref.Message, fd pref.FieldDescriptor) error {
	var val pref.Value
	var err error
	switch fd.Kind() {
	case pref.MessageKind, pref.GroupKind:
		val = m.NewField(fd)
		err = d.unmarshalMessage(val.Message(), false)
	default:
		val, err = d.unmarshalScalar(fd)
	}

	if err != nil {
		return err
	}
	m.Set(fd, val)
	return nil
}

unmarshalScalar unmarshals to a scalar/enum protoreflect.Value specified by the given FieldDescriptor.

func (d decoder) unmarshalScalar(fd pref.FieldDescriptor) (pref.Value, error) {
	const b32 int = 32
	const b64 int = 64

	tok, err := d.Read()
	if err != nil {
		return pref.Value{}, err
	}

	kind := fd.Kind()
	switch kind {
	case pref.BoolKind:
		if tok.Kind() == json.Bool {
			return pref.ValueOfBool(tok.Bool()), nil
		}

	case pref.Int32Kind, pref.Sint32Kind, pref.Sfixed32Kind:
		if v, ok := unmarshalInt(tok, b32); ok {
			return v, nil
		}

	case pref.Int64Kind, pref.Sint64Kind, pref.Sfixed64Kind:
		if v, ok := unmarshalInt(tok, b64); ok {
			return v, nil
		}

	case pref.Uint32Kind, pref.Fixed32Kind:
		if v, ok := unmarshalUint(tok, b32); ok {
			return v, nil
		}

	case pref.Uint64Kind, pref.Fixed64Kind:
		if v, ok := unmarshalUint(tok, b64); ok {
			return v, nil
		}

	case pref.FloatKind:
		if v, ok := unmarshalFloat(tok, b32); ok {
			return v, nil
		}

	case pref.DoubleKind:
		if v, ok := unmarshalFloat(tok, b64); ok {
			return v, nil
		}

	case pref.StringKind:
		if tok.Kind() == json.String {
			return pref.ValueOfString(tok.ParsedString()), nil
		}

	case pref.BytesKind:
		if v, ok := unmarshalBytes(tok); ok {
			return v, nil
		}

	case pref.EnumKind:
		if v, ok := unmarshalEnum(tok, fd); ok {
			return v, nil
		}

	default:
		panic(fmt.Sprintf("unmarshalScalar: invalid scalar kind %v", kind))
	}

	return pref.Value{}, d.newError(tok.Pos(), "invalid value for %v type: %v", kind, tok.RawString())
}

func unmarshalInt(tok json.Token, bitSize int) (pref.Value, bool) {
	switch tok.Kind() {
	case json.Number:
		return getInt(tok, bitSize)

Decode number from string.

		s := strings.TrimSpace(tok.ParsedString())
		if len(s) != len(tok.ParsedString()) {
			return pref.Value{}, false
		}
		dec := json.NewDecoder([]byte(s))
		tok, err := dec.Read()
		if err != nil {
			return pref.Value{}, false
		}
		return getInt(tok, bitSize)
	}
	return pref.Value{}, false
}

func getInt(tok json.Token, bitSize int) (pref.Value, bool) {
	n, ok := tok.Int(bitSize)
	if !ok {
		return pref.Value{}, false
	}
	if bitSize == 32 {
		return pref.ValueOfInt32(int32(n)), true
	}
	return pref.ValueOfInt64(n), true
}

func unmarshalUint(tok json.Token, bitSize int) (pref.Value, bool) {
	switch tok.Kind() {
	case json.Number:
		return getUint(tok, bitSize)

Decode number from string.

		s := strings.TrimSpace(tok.ParsedString())
		if len(s) != len(tok.ParsedString()) {
			return pref.Value{}, false
		}
		dec := json.NewDecoder([]byte(s))
		tok, err := dec.Read()
		if err != nil {
			return pref.Value{}, false
		}
		return getUint(tok, bitSize)
	}
	return pref.Value{}, false
}

func getUint(tok json.Token, bitSize int) (pref.Value, bool) {
	n, ok := tok.Uint(bitSize)
	if !ok {
		return pref.Value{}, false
	}
	if bitSize == 32 {
		return pref.ValueOfUint32(uint32(n)), true
	}
	return pref.ValueOfUint64(n), true
}

func unmarshalFloat(tok json.Token, bitSize int) (pref.Value, bool) {
	switch tok.Kind() {
	case json.Number:
		return getFloat(tok, bitSize)

	case json.String:
		s := tok.ParsedString()
		switch s {
		case "NaN":
			if bitSize == 32 {
				return pref.ValueOfFloat32(float32(math.NaN())), true
			}
			return pref.ValueOfFloat64(math.NaN()), true
		case "Infinity":
			if bitSize == 32 {
				return pref.ValueOfFloat32(float32(math.Inf(+1))), true
			}
			return pref.ValueOfFloat64(math.Inf(+1)), true
		case "-Infinity":
			if bitSize == 32 {
				return pref.ValueOfFloat32(float32(math.Inf(-1))), true
			}
			return pref.ValueOfFloat64(math.Inf(-1)), true
		}

Decode number from string.

		if len(s) != len(strings.TrimSpace(s)) {
			return pref.Value{}, false
		}
		dec := json.NewDecoder([]byte(s))
		tok, err := dec.Read()
		if err != nil {
			return pref.Value{}, false
		}
		return getFloat(tok, bitSize)
	}
	return pref.Value{}, false
}

func getFloat(tok json.Token, bitSize int) (pref.Value, bool) {
	n, ok := tok.Float(bitSize)
	if !ok {
		return pref.Value{}, false
	}
	if bitSize == 32 {
		return pref.ValueOfFloat32(float32(n)), true
	}
	return pref.ValueOfFloat64(n), true
}

func unmarshalBytes(tok json.Token) (pref.Value, bool) {
	if tok.Kind() != json.String {
		return pref.Value{}, false
	}

	s := tok.ParsedString()
	enc := base64.StdEncoding
	if strings.ContainsAny(s, "-_") {
		enc = base64.URLEncoding
	}
	if len(s)%4 != 0 {
		enc = enc.WithPadding(base64.NoPadding)
	}
	b, err := enc.DecodeString(s)
	if err != nil {
		return pref.Value{}, false
	}
	return pref.ValueOfBytes(b), true
}

func unmarshalEnum(tok json.Token, fd pref.FieldDescriptor) (pref.Value, bool) {
	switch tok.Kind() {

Lookup EnumNumber based on name.

		s := tok.ParsedString()
		if enumVal := fd.Enum().Values().ByName(pref.Name(s)); enumVal != nil {
			return pref.ValueOfEnum(enumVal.Number()), true
		}

	case json.Number:
		if n, ok := tok.Int(32); ok {
			return pref.ValueOfEnum(pref.EnumNumber(n)), true
		}

This is only valid for google.protobuf.NullValue.

		if isNullValue(fd) {
			return pref.ValueOfEnum(0), true
		}
	}

	return pref.Value{}, false
}

func (d decoder) unmarshalList(list pref.List, fd pref.FieldDescriptor) error {
	tok, err := d.Read()
	if err != nil {
		return err
	}
	if tok.Kind() != json.ArrayOpen {
		return d.unexpectedTokenError(tok)
	}

	switch fd.Kind() {
	case pref.MessageKind, pref.GroupKind:
		for {
			tok, err := d.Peek()
			if err != nil {
				return err
			}

			if tok.Kind() == json.ArrayClose {
				d.Read()
				return nil
			}

			val := list.NewElement()
			if err := d.unmarshalMessage(val.Message(), false); err != nil {
				return err
			}
			list.Append(val)
		}
	default:
		for {
			tok, err := d.Peek()
			if err != nil {
				return err
			}

			if tok.Kind() == json.ArrayClose {
				d.Read()
				return nil
			}

			val, err := d.unmarshalScalar(fd)
			if err != nil {
				return err
			}
			list.Append(val)
		}
	}

	return nil
}

func (d decoder) unmarshalMap(mmap pref.Map, fd pref.FieldDescriptor) error {
	tok, err := d.Read()
	if err != nil {
		return err
	}
	if tok.Kind() != json.ObjectOpen {
		return d.unexpectedTokenError(tok)
	}

Determine ahead whether map entry is a scalar type or a message type in order to call the appropriate unmarshalMapValue func inside the for loop below.

	var unmarshalMapValue func() (pref.Value, error)
	switch fd.MapValue().Kind() {
	case pref.MessageKind, pref.GroupKind:
		unmarshalMapValue = func() (pref.Value, error) {
			val := mmap.NewValue()
			if err := d.unmarshalMessage(val.Message(), false); err != nil {
				return pref.Value{}, err
			}
			return val, nil
		}
	default:
		unmarshalMapValue = func() (pref.Value, error) {
			return d.unmarshalScalar(fd.MapValue())
		}
	}

Loop:

Read field name.

		tok, err := d.Read()
		if err != nil {
			return err
		}
		switch tok.Kind() {
		default:
			return d.unexpectedTokenError(tok)
		case json.ObjectClose:
			break Loop

Continue.

Unmarshal field name.

		pkey, err := d.unmarshalMapKey(tok, fd.MapKey())
		if err != nil {
			return err
		}

Check for duplicate field name.

		if mmap.Has(pkey) {
			return d.newError(tok.Pos(), "duplicate map key %v", tok.RawString())
		}

Read and unmarshal field value.

		pval, err := unmarshalMapValue()
		if err != nil {
			return err
		}

		mmap.Set(pkey, pval)
	}

	return nil
}

unmarshalMapKey converts given token of Name kind into a protoreflect.MapKey. A map key type is any integral or string type.

func (d decoder) unmarshalMapKey(tok json.Token, fd pref.FieldDescriptor) (pref.MapKey, error) {
	const b32 = 32
	const b64 = 64
	const base10 = 10

	name := tok.Name()
	kind := fd.Kind()
	switch kind {
	case pref.StringKind:
		return pref.ValueOfString(name).MapKey(), nil

	case pref.BoolKind:
		switch name {
		case "true":
			return pref.ValueOfBool(true).MapKey(), nil
		case "false":
			return pref.ValueOfBool(false).MapKey(), nil
		}

	case pref.Int32Kind, pref.Sint32Kind, pref.Sfixed32Kind:
		if n, err := strconv.ParseInt(name, base10, b32); err == nil {
			return pref.ValueOfInt32(int32(n)).MapKey(), nil
		}

	case pref.Int64Kind, pref.Sint64Kind, pref.Sfixed64Kind:
		if n, err := strconv.ParseInt(name, base10, b64); err == nil {
			return pref.ValueOfInt64(int64(n)).MapKey(), nil
		}

	case pref.Uint32Kind, pref.Fixed32Kind:
		if n, err := strconv.ParseUint(name, base10, b32); err == nil {
			return pref.ValueOfUint32(uint32(n)).MapKey(), nil
		}

	case pref.Uint64Kind, pref.Fixed64Kind:
		if n, err := strconv.ParseUint(name, base10, b64); err == nil {
			return pref.ValueOfUint64(uint64(n)).MapKey(), nil
		}

	default:
		panic(fmt.Sprintf("invalid kind for map key: %v", kind))
	}

	return pref.MapKey{}, d.newError(tok.Pos(), "invalid value for %v key: %s", kind, tok.RawString())