encoding: unify MessageSet extension handling logic

This CL unifies common MessageSet logic in prototext and protojson
into the messageset package. While we are at it, also enable
MessageSet support only if the proto1_legacy build flag is enabled.

Change-Id: I1a7d475e8bb1dad61ecd286df45e4239e5bef072
Reviewed-on: https://go-review.googlesource.com/c/protobuf/+/185898
Reviewed-by: Damien Neil <dneil@google.com>

encoding/protojson/decode.go

@@ -12,7 +12,9 @@ import (
 	"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/pragma"
 	"google.golang.org/protobuf/internal/set"
 	"google.golang.org/protobuf/proto"
@@ -136,13 +138,14 @@ func (o UnmarshalOptions) unmarshalMessage(m pref.Message, skipTypeURL bool) err
 
 // unmarshalFields unmarshals the fields into the given protoreflect.Message.
 func (o UnmarshalOptions) unmarshalFields(m pref.Message, skipTypeURL bool) error {
+	messageDesc := m.Descriptor()
+	if !flags.Proto1Legacy && messageset.IsMessageSet(messageDesc) {
+		return errors.New("no support for proto1 MessageSets")
+	}
+
 	var seenNums set.Ints
 	var seenOneofs set.Ints
-
-	messageDesc := m.Descriptor()
 	fieldDescs := messageDesc.Fields()
-
-Loop:
 	for {
 		// Read field name.
 		jval, err := o.decoder.Read()
@@ -153,7 +156,7 @@ Loop:
 		default:
 			return unexpectedJSONError{jval}
 		case json.EndObject:
-			break Loop
+			return nil
 		case json.Name:
 			// Continue below.
 		}
@@ -243,8 +246,6 @@ Loop:
 			}
 		}
 	}
-
-	return nil
 }
 
 // findExtension returns protoreflect.ExtensionType from the resolver if found.
@@ -253,13 +254,7 @@ func (o UnmarshalOptions) findExtension(xtName pref.FullName) (pref.ExtensionTyp
 	if err == nil {
 		return xt, nil
 	}
-
-	// Check if this is a MessageSet extension field.
-	xt, err = o.Resolver.FindExtensionByName(xtName + ".message_set_extension")
-	if err == nil && isMessageSetExtension(xt) {
-		return xt, nil
-	}
-	return nil, protoregistry.NotFound
+	return messageset.FindMessageSetExtension(o.Resolver, xtName)
 }
 
 func isKnownValue(fd pref.FieldDescriptor) bool {

encoding/protojson/decode_test.go

@@ -1296,6 +1296,17 @@ func TestUnmarshal(t *testing.T) {
 		inputMessage: &pb2.Extensions{},
 		inputText:    `{ "[pb2.invalid_message_field]": true }`,
 		wantErr:      true,
+	}, {
+		desc:         "extensions of repeated field contains null",
+		inputMessage: &pb2.Extensions{},
+		inputText: `{
+  "[pb2.ExtensionsContainer.rpt_ext_nested]": [
+    {"optString": "one"},
+	null,
+    {"optString": "three"}
+  ],
+}`,
+		wantErr: true,
 	}, {
 		desc:         "MessageSet",
 		inputMessage: &pb2.MessageSet{},
@@ -1323,17 +1334,7 @@ func TestUnmarshal(t *testing.T) {
 			})
 			return m
 		}(),
-	}, {
-		desc:         "extensions of repeated field contains null",
-		inputMessage: &pb2.Extensions{},
-		inputText: `{
-  "[pb2.ExtensionsContainer.rpt_ext_nested]": [
-    {"optString": "one"},
-	null,
-    {"optString": "three"}
-  ],
-}`,
-		wantErr: true,
+		skip: !flags.Proto1Legacy,
 	}, {
 		desc:         "not real MessageSet 1",
 		inputMessage: &pb2.FakeMessageSet{},
@@ -1349,6 +1350,7 @@ func TestUnmarshal(t *testing.T) {
 			})
 			return m
 		}(),
+		skip: !flags.Proto1Legacy,
 	}, {
 		desc:         "not real MessageSet 2",
 		inputMessage: &pb2.FakeMessageSet{},
@@ -1358,6 +1360,7 @@ func TestUnmarshal(t *testing.T) {
   }
 }`,
 		wantErr: true,
+		skip:    !flags.Proto1Legacy,
 	}, {
 		desc:         "not real MessageSet 3",
 		inputMessage: &pb2.MessageSet{},
@@ -1373,6 +1376,7 @@ func TestUnmarshal(t *testing.T) {
 			})
 			return m
 		}(),
+		skip: !flags.Proto1Legacy,
 	}, {
 		desc:         "Empty",
 		inputMessage: &emptypb.Empty{},

encoding/protojson/encode.go

@@ -10,6 +10,9 @@ import (
 	"sort"
 
 	"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/pragma"
 	"google.golang.org/protobuf/proto"
 	pref "google.golang.org/protobuf/reflect/protoreflect"
@@ -84,8 +87,13 @@ func (o MarshalOptions) marshalMessage(m pref.Message) error {
 
 // marshalFields marshals the fields in the given protoreflect.Message.
 func (o MarshalOptions) marshalFields(m pref.Message) error {
+	messageDesc := m.Descriptor()
+	if !flags.Proto1Legacy && messageset.IsMessageSet(messageDesc) {
+		return errors.New("no support for proto1 MessageSets")
+	}
+
 	// Marshal out known fields.
-	fieldDescs := m.Descriptor().Fields()
+	fieldDescs := messageDesc.Fields()
 	for i := 0; i < fieldDescs.Len(); i++ {
 		fd := fieldDescs.Get(i)
 		if !m.Has(fd) {
@@ -257,10 +265,10 @@ func (o MarshalOptions) marshalExtensions(m pref.Message) error {
 			return true
 		}
 
-		// If extended type is a MessageSet, set field name to be the message type name.
+		// For MessageSet extensions, the name used is the parent message.
 		name := fd.FullName()
-		if isMessageSetExtension(fd) {
-			name = fd.Message().FullName()
+		if messageset.IsMessageSetExtension(fd) {
+			name = name.Parent()
 		}
 
 		// Use [name] format for JSON field name.
@@ -291,19 +299,3 @@ func (o MarshalOptions) marshalExtensions(m pref.Message) error {
 	}
 	return nil
 }
-
-// isMessageSetExtension reports whether extension extends a message set.
-func isMessageSetExtension(fd pref.FieldDescriptor) bool {
-	if fd.Name() != "message_set_extension" {
-		return false
-	}
-	md := fd.Message()
-	if md == nil {
-		return false
-	}
-	if fd.FullName().Parent() != md.FullName() {
-		return false
-	}
-	xmd, ok := fd.ContainingMessage().(interface{ IsMessageSet() bool })
-	return ok && xmd.IsMessageSet()
-}

encoding/protojson/encode_test.go

@@ -12,6 +12,7 @@ import (
 	"github.com/google/go-cmp/cmp"
 	"google.golang.org/protobuf/encoding/protojson"
 	"google.golang.org/protobuf/internal/encoding/pack"
+	"google.golang.org/protobuf/internal/flags"
 	pimpl "google.golang.org/protobuf/internal/impl"
 	"google.golang.org/protobuf/proto"
 	preg "google.golang.org/protobuf/reflect/protoregistry"
@@ -40,6 +41,7 @@ func TestMarshal(t *testing.T) {
 		input   proto.Message
 		want    string
 		wantErr bool // TODO: Verify error message substring.
+		skip    bool
 	}{{
 		desc:  "proto2 optional scalars not set",
 		input: &pb2.Scalars{},
@@ -1038,6 +1040,7 @@ func TestMarshal(t *testing.T) {
     "optString": "not a messageset extension"
   }
 }`,
+		skip: !flags.Proto1Legacy,
 	}, {
 		desc: "not real MessageSet 1",
 		input: func() proto.Message {
@@ -1052,6 +1055,7 @@ func TestMarshal(t *testing.T) {
     "optString": "not a messageset extension"
   }
 }`,
+		skip: !flags.Proto1Legacy,
 	}, {
 		desc: "not real MessageSet 2",
 		input: func() proto.Message {
@@ -1066,6 +1070,7 @@ func TestMarshal(t *testing.T) {
     "optString": "another not a messageset extension"
   }
 }`,
+		skip: !flags.Proto1Legacy,
 	}, {
 		desc:  "BoolValue empty",
 		input: &wrapperspb.BoolValue{},
@@ -1898,6 +1903,9 @@ func TestMarshal(t *testing.T) {
 
 	for _, tt := range tests {
 		tt := tt
+		if tt.skip {
+			continue
+		}
 		t.Run(tt.desc, func(t *testing.T) {
 			// Use 2-space indentation on all MarshalOptions.
 			tt.mo.Indent = "  "

encoding/prototext/decode.go

@@ -9,9 +9,11 @@ import (
 	"strings"
 	"unicode/utf8"
 
+	"google.golang.org/protobuf/internal/encoding/messageset"
 	"google.golang.org/protobuf/internal/encoding/text"
 	"google.golang.org/protobuf/internal/errors"
 	"google.golang.org/protobuf/internal/fieldnum"
+	"google.golang.org/protobuf/internal/flags"
 	"google.golang.org/protobuf/internal/pragma"
 	"google.golang.org/protobuf/internal/set"
 	"google.golang.org/protobuf/proto"
@@ -74,17 +76,18 @@ func (o UnmarshalOptions) Unmarshal(b []byte, m proto.Message) error {
 // unmarshalMessage unmarshals a [][2]text.Value message into the given protoreflect.Message.
 func (o UnmarshalOptions) unmarshalMessage(tmsg [][2]text.Value, m pref.Message) error {
 	messageDesc := m.Descriptor()
+	if !flags.Proto1Legacy && messageset.IsMessageSet(messageDesc) {
+		return errors.New("no support for proto1 MessageSets")
+	}
 
 	// Handle expanded Any message.
 	if messageDesc.FullName() == "google.protobuf.Any" && isExpandedAny(tmsg) {
 		return o.unmarshalAny(tmsg[0], m)
 	}
 
-	fieldDescs := messageDesc.Fields()
-	reservedNames := messageDesc.ReservedNames()
 	var seenNums set.Ints
 	var seenOneofs set.Ints
-
+	fieldDescs := messageDesc.Fields()
 	for _, tfield := range tmsg {
 		tkey := tfield[0]
 		tval := tfield[1]
@@ -128,7 +131,7 @@ func (o UnmarshalOptions) unmarshalMessage(tmsg [][2]text.Value, m pref.Message)
 
 		if fd == nil {
 			// Ignore reserved names.
-			if reservedNames.Has(name) {
+			if messageDesc.ReservedNames().Has(name) {
 				continue
 			}
 			// TODO: Can provide option to ignore unknown message fields.
@@ -193,13 +196,7 @@ func (o UnmarshalOptions) findExtension(xtName pref.FullName) (pref.ExtensionTyp
 	if err == nil {
 		return xt, nil
 	}
-
-	// Check if this is a MessageSet extension field.
-	xt, err = o.Resolver.FindExtensionByName(xtName + ".message_set_extension")
-	if err == nil && isMessageSetExtension(xt) {
-		return xt, nil
-	}
-	return nil, protoregistry.NotFound
+	return messageset.FindMessageSetExtension(o.Resolver, xtName)
 }
 
 // unmarshalSingular unmarshals given text.Value into the non-repeated field.

encoding/prototext/decode_test.go

@@ -1310,6 +1310,7 @@ opt_int32: 42
 			})
 			return m
 		}(),
+		skip: !flags.Proto1Legacy,
 	}, {
 		desc:         "not real MessageSet 1",
 		inputMessage: &pb2.FakeMessageSet{},
@@ -1325,6 +1326,7 @@ opt_int32: 42
 			})
 			return m
 		}(),
+		skip: !flags.Proto1Legacy,
 	}, {
 		desc:         "not real MessageSet 2",
 		inputMessage: &pb2.FakeMessageSet{},
@@ -1334,6 +1336,7 @@ opt_int32: 42
 }
 `,
 		wantErr: true,
+		skip:    !flags.Proto1Legacy,
 	}, {
 		desc:         "not real MessageSet 3",
 		inputMessage: &pb2.MessageSet{},
@@ -1348,6 +1351,7 @@ opt_int32: 42
 			})
 			return m
 		}(),
+		skip: !flags.Proto1Legacy,
 	}, {
 		desc:         "Any not expanded",
 		inputMessage: &anypb.Any{},

encoding/prototext/encode.go

@@ -9,10 +9,12 @@ import (
 	"sort"
 	"unicode/utf8"
 
+	"google.golang.org/protobuf/internal/encoding/messageset"
 	"google.golang.org/protobuf/internal/encoding/text"
 	"google.golang.org/protobuf/internal/encoding/wire"
 	"google.golang.org/protobuf/internal/errors"
 	"google.golang.org/protobuf/internal/fieldnum"
+	"google.golang.org/protobuf/internal/flags"
 	"google.golang.org/protobuf/internal/mapsort"
 	"google.golang.org/protobuf/internal/pragma"
 	"google.golang.org/protobuf/proto"
@@ -72,8 +74,10 @@ func (o MarshalOptions) Marshal(m proto.Message) ([]byte, error) {
 
 // marshalMessage converts a protoreflect.Message to a text.Value.
 func (o MarshalOptions) marshalMessage(m pref.Message) (text.Value, error) {
-	var msgFields [][2]text.Value
 	messageDesc := m.Descriptor()
+	if !flags.Proto1Legacy && messageset.IsMessageSet(messageDesc) {
+		return text.Value{}, errors.New("no support for proto1 MessageSets")
+	}
 
 	// Handle Any expansion.
 	if messageDesc.FullName() == "google.protobuf.Any" {
@@ -85,6 +89,7 @@ func (o MarshalOptions) marshalMessage(m pref.Message) (text.Value, error) {
 	}
 
 	// Handle known fields.
+	var msgFields [][2]text.Value
 	fieldDescs := messageDesc.Fields()
 	size := fieldDescs.Len()
 	for i := 0; i < size; i++ {
@@ -253,10 +258,10 @@ func (o MarshalOptions) appendExtensions(msgFields [][2]text.Value, m pref.Messa
 			return true
 		}
 
-		// If extended type is a MessageSet, set field name to be the message type name.
+		// For MessageSet extensions, the name used is the parent message.
 		name := fd.FullName()
-		if isMessageSetExtension(fd) {
-			name = fd.Message().FullName()
+		if messageset.IsMessageSetExtension(fd) {
+			name = name.Parent()
 		}
 
 		// Use string type to produce [name] format.
@@ -279,22 +284,6 @@ func (o MarshalOptions) appendExtensions(msgFields [][2]text.Value, m pref.Messa
 	return append(msgFields, entries...), nil
 }
 
-// isMessageSetExtension reports whether extension extends a message set.
-func isMessageSetExtension(fd pref.FieldDescriptor) bool {
-	if fd.Name() != "message_set_extension" {
-		return false
-	}
-	md := fd.Message()
-	if md == nil {
-		return false
-	}
-	if fd.FullName().Parent() != md.FullName() {
-		return false
-	}
-	xmd, ok := fd.ContainingMessage().(interface{ IsMessageSet() bool })
-	return ok && xmd.IsMessageSet()
-}
-
 // appendUnknown parses the given []byte and appends field(s) into the given fields slice.
 // This function assumes proper encoding in the given []byte.
 func appendUnknown(fields [][2]text.Value, b []byte) [][2]text.Value {

encoding/prototext/encode_test.go

@@ -12,6 +12,7 @@ import (
 	"google.golang.org/protobuf/encoding/prototext"
 	"google.golang.org/protobuf/internal/detrand"
 	"google.golang.org/protobuf/internal/encoding/pack"
+	"google.golang.org/protobuf/internal/flags"
 	pimpl "google.golang.org/protobuf/internal/impl"
 	"google.golang.org/protobuf/proto"
 	preg "google.golang.org/protobuf/reflect/protoregistry"
@@ -39,6 +40,7 @@ func TestMarshal(t *testing.T) {
 		input   proto.Message
 		want    string
 		wantErr bool // TODO: Verify error message content.
+		skip    bool
 	}{{
 		desc:  "proto2 optional scalars not set",
 		input: &pb2.Scalars{},
@@ -1082,6 +1084,7 @@ opt_int32: 42
   opt_string: "not a messageset extension"
 }
 `,
+		skip: !flags.Proto1Legacy,
 	}, {
 		desc: "not real MessageSet 1",
 		input: func() proto.Message {
@@ -1095,6 +1098,7 @@ opt_int32: 42
   opt_string: "not a messageset extension"
 }
 `,
+		skip: !flags.Proto1Legacy,
 	}, {
 		desc: "not real MessageSet 2",
 		input: func() proto.Message {
@@ -1108,6 +1112,7 @@ opt_int32: 42
   opt_string: "another not a messageset extension"
 }
 `,
+		skip: !flags.Proto1Legacy,
 	}, {
 		desc: "Any not expanded",
 		mo: prototext.MarshalOptions{
@@ -1201,6 +1206,9 @@ value: "\x80"
 
 	for _, tt := range tests {
 		tt := tt
+		if tt.skip {
+			continue
+		}
 		t.Run(tt.desc, func(t *testing.T) {
 			// Use 2-space indentation on all MarshalOptions.
 			tt.mo.Indent = "  "

internal/encoding/messageset/messageset.go

@@ -9,6 +9,7 @@ import (
 	"google.golang.org/protobuf/internal/encoding/wire"
 	"google.golang.org/protobuf/internal/errors"
 	pref "google.golang.org/protobuf/reflect/protoreflect"
+	preg "google.golang.org/protobuf/reflect/protoregistry"
 )
 
 // The MessageSet wire format is equivalent to a message defiend as follows,
@@ -28,12 +29,48 @@ const (
 	FieldMessage = wire.Number(3)
 )
 
+// ExtensionName is the field name for extensions of MessageSet.
+//
+// A valid MessageSet extension must be of the form:
+//	message MyMessage {
+//		extend proto2.bridge.MessageSet {
+//			optional MyMessage message_set_extension = 1234;
+//		}
+//		...
+//	}
+const ExtensionName = "message_set_extension"
+
 // IsMessageSet returns whether the message uses the MessageSet wire format.
 func IsMessageSet(md pref.MessageDescriptor) bool {
 	xmd, ok := md.(interface{ IsMessageSet() bool })
 	return ok && xmd.IsMessageSet()
 }
 
+// IsMessageSetExtension reports this field extends a MessageSet.
+func IsMessageSetExtension(fd pref.FieldDescriptor) bool {
+	if fd.Name() != ExtensionName {
+		return false
+	}
+	if fd.FullName().Parent() != fd.Message().FullName() {
+		return false
+	}
+	return IsMessageSet(fd.ContainingMessage())
+}
+
+// FindMessageSetExtension locates a MessageSet extension field by name.
+// In text and JSON formats, the extension name used is the message itself.
+// The extension field name is derived by appending ExtensionName.
+func FindMessageSetExtension(r preg.ExtensionTypeResolver, s pref.FullName) (pref.ExtensionType, error) {
+	xt, err := r.FindExtensionByName(s.Append(ExtensionName))
+	if err != nil {
+		return nil, err
+	}
+	if !IsMessageSetExtension(xt) {
+		return nil, preg.NotFound
+	}
+	return xt, nil
+}
+
 // SizeField returns the size of a MessageSet item field containing an extension
 // with the given field number, not counting the contents of the message subfield.
 func SizeField(num wire.Number) int {