protogen, encoding/jsonpb, encoding/textpb: rename packages

Rename encoding/*pb to follow the convention of prefixing package names
with 'proto':

	google.golang.org/protobuf/encoding/protojson
	google.golang.org/protobuf/encoding/prototext

Move protogen under a compiler/ directory, just in case we ever do add
more compiler-related packages.

	google.golang.org/protobuf/compiler/protogen

Change-Id: I31010cb5cabcea8274fffcac468477b58b56e8eb
Reviewed-on: https://go-review.googlesource.com/c/protobuf/+/177178
Reviewed-by: Joe Tsai <thebrokentoaster@gmail.com>
diff --git a/encoding/prototext/encode_test.go b/encoding/prototext/encode_test.go
new file mode 100644
index 0000000..b2fc57b
--- /dev/null
+++ b/encoding/prototext/encode_test.go
@@ -0,0 +1,1304 @@
+// Copyright 2018 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 prototext_test
+
+import (
+	"bytes"
+	"encoding/hex"
+	"math"
+	"strings"
+	"testing"
+
+	"github.com/google/go-cmp/cmp"
+	"github.com/google/go-cmp/cmp/cmpopts"
+	"google.golang.org/protobuf/encoding/prototext"
+	"google.golang.org/protobuf/internal/detrand"
+	"google.golang.org/protobuf/internal/encoding/pack"
+	"google.golang.org/protobuf/internal/encoding/wire"
+	pimpl "google.golang.org/protobuf/internal/impl"
+	"google.golang.org/protobuf/internal/scalar"
+	"google.golang.org/protobuf/proto"
+	preg "google.golang.org/protobuf/reflect/protoregistry"
+	"google.golang.org/protobuf/runtime/protoiface"
+
+	"google.golang.org/protobuf/encoding/testprotos/pb2"
+	"google.golang.org/protobuf/encoding/testprotos/pb3"
+	knownpb "google.golang.org/protobuf/types/known"
+)
+
+func init() {
+	// Disable detrand to enable direct comparisons on outputs.
+	detrand.Disable()
+}
+
+// splitLines is a cmpopts.Option for comparing strings with line breaks.
+var splitLines = cmpopts.AcyclicTransformer("SplitLines", func(s string) []string {
+	return strings.Split(s, "\n")
+})
+
+func pb2Enum(i int32) *pb2.Enum {
+	p := new(pb2.Enum)
+	*p = pb2.Enum(i)
+	return p
+}
+
+func pb2Enums_NestedEnum(i int32) *pb2.Enums_NestedEnum {
+	p := new(pb2.Enums_NestedEnum)
+	*p = pb2.Enums_NestedEnum(i)
+	return p
+}
+
+func setExtension(m proto.Message, xd *protoiface.ExtensionDescV1, val interface{}) {
+	knownFields := m.ProtoReflect().KnownFields()
+	extTypes := knownFields.ExtensionTypes()
+	extTypes.Register(xd.Type)
+	if val == nil {
+		return
+	}
+	pval := xd.Type.ValueOf(val)
+	knownFields.Set(wire.Number(xd.Field), pval)
+}
+
+// dhex decodes a hex-string and returns the bytes and panics if s is invalid.
+func dhex(s string) []byte {
+	b, err := hex.DecodeString(s)
+	if err != nil {
+		panic(err)
+	}
+	return b
+}
+
+func TestMarshal(t *testing.T) {
+	tests := []struct {
+		desc    string
+		mo      prototext.MarshalOptions
+		input   proto.Message
+		want    string
+		wantErr bool // TODO: Verify error message content.
+	}{{
+		desc:  "proto2 optional scalars not set",
+		input: &pb2.Scalars{},
+		want:  "\n",
+	}, {
+		desc:  "proto3 scalars not set",
+		input: &pb3.Scalars{},
+		want:  "\n",
+	}, {
+		desc: "proto2 optional scalars set to zero values",
+		input: &pb2.Scalars{
+			OptBool:     scalar.Bool(false),
+			OptInt32:    scalar.Int32(0),
+			OptInt64:    scalar.Int64(0),
+			OptUint32:   scalar.Uint32(0),
+			OptUint64:   scalar.Uint64(0),
+			OptSint32:   scalar.Int32(0),
+			OptSint64:   scalar.Int64(0),
+			OptFixed32:  scalar.Uint32(0),
+			OptFixed64:  scalar.Uint64(0),
+			OptSfixed32: scalar.Int32(0),
+			OptSfixed64: scalar.Int64(0),
+			OptFloat:    scalar.Float32(0),
+			OptDouble:   scalar.Float64(0),
+			OptBytes:    []byte{},
+			OptString:   scalar.String(""),
+		},
+		want: `opt_bool: false
+opt_int32: 0
+opt_int64: 0
+opt_uint32: 0
+opt_uint64: 0
+opt_sint32: 0
+opt_sint64: 0
+opt_fixed32: 0
+opt_fixed64: 0
+opt_sfixed32: 0
+opt_sfixed64: 0
+opt_float: 0
+opt_double: 0
+opt_bytes: ""
+opt_string: ""
+`,
+	}, {
+		desc: "proto3 scalars set to zero values",
+		input: &pb3.Scalars{
+			SBool:     false,
+			SInt32:    0,
+			SInt64:    0,
+			SUint32:   0,
+			SUint64:   0,
+			SSint32:   0,
+			SSint64:   0,
+			SFixed32:  0,
+			SFixed64:  0,
+			SSfixed32: 0,
+			SSfixed64: 0,
+			SFloat:    0,
+			SDouble:   0,
+			SBytes:    []byte{},
+			SString:   "",
+		},
+		want: "\n",
+	}, {
+		desc: "proto2 optional scalars set to some values",
+		input: &pb2.Scalars{
+			OptBool:     scalar.Bool(true),
+			OptInt32:    scalar.Int32(0xff),
+			OptInt64:    scalar.Int64(0xdeadbeef),
+			OptUint32:   scalar.Uint32(47),
+			OptUint64:   scalar.Uint64(0xdeadbeef),
+			OptSint32:   scalar.Int32(-1001),
+			OptSint64:   scalar.Int64(-0xffff),
+			OptFixed64:  scalar.Uint64(64),
+			OptSfixed32: scalar.Int32(-32),
+			OptFloat:    scalar.Float32(1.02),
+			OptDouble:   scalar.Float64(1.0199999809265137),
+			OptBytes:    []byte("\xe8\xb0\xb7\xe6\xad\x8c"),
+			OptString:   scalar.String("谷歌"),
+		},
+		want: `opt_bool: true
+opt_int32: 255
+opt_int64: 3735928559
+opt_uint32: 47
+opt_uint64: 3735928559
+opt_sint32: -1001
+opt_sint64: -65535
+opt_fixed64: 64
+opt_sfixed32: -32
+opt_float: 1.02
+opt_double: 1.0199999809265137
+opt_bytes: "谷歌"
+opt_string: "谷歌"
+`,
+	}, {
+		desc: "string with invalid UTF-8",
+		input: &pb3.Scalars{
+			SString: "abc\xff",
+		},
+		want: `s_string: "abc\xff"
+`,
+		wantErr: true,
+	}, {
+		desc: "float nan",
+		input: &pb3.Scalars{
+			SFloat: float32(math.NaN()),
+		},
+		want: "s_float: nan\n",
+	}, {
+		desc: "float positive infinity",
+		input: &pb3.Scalars{
+			SFloat: float32(math.Inf(1)),
+		},
+		want: "s_float: inf\n",
+	}, {
+		desc: "float negative infinity",
+		input: &pb3.Scalars{
+			SFloat: float32(math.Inf(-1)),
+		},
+		want: "s_float: -inf\n",
+	}, {
+		desc: "double nan",
+		input: &pb3.Scalars{
+			SDouble: math.NaN(),
+		},
+		want: "s_double: nan\n",
+	}, {
+		desc: "double positive infinity",
+		input: &pb3.Scalars{
+			SDouble: math.Inf(1),
+		},
+		want: "s_double: inf\n",
+	}, {
+		desc: "double negative infinity",
+		input: &pb3.Scalars{
+			SDouble: math.Inf(-1),
+		},
+		want: "s_double: -inf\n",
+	}, {
+		desc:  "proto2 enum not set",
+		input: &pb2.Enums{},
+		want:  "\n",
+	}, {
+		desc: "proto2 enum set to zero value",
+		input: &pb2.Enums{
+			OptEnum:       pb2Enum(0),
+			OptNestedEnum: pb2Enums_NestedEnum(0),
+		},
+		want: `opt_enum: 0
+opt_nested_enum: 0
+`,
+	}, {
+		desc: "proto2 enum",
+		input: &pb2.Enums{
+			OptEnum:       pb2.Enum_ONE.Enum(),
+			OptNestedEnum: pb2.Enums_UNO.Enum(),
+		},
+		want: `opt_enum: ONE
+opt_nested_enum: UNO
+`,
+	}, {
+		desc: "proto2 enum set to numeric values",
+		input: &pb2.Enums{
+			OptEnum:       pb2Enum(2),
+			OptNestedEnum: pb2Enums_NestedEnum(2),
+		},
+		want: `opt_enum: TWO
+opt_nested_enum: DOS
+`,
+	}, {
+		desc: "proto2 enum set to unnamed numeric values",
+		input: &pb2.Enums{
+			OptEnum:       pb2Enum(101),
+			OptNestedEnum: pb2Enums_NestedEnum(-101),
+		},
+		want: `opt_enum: 101
+opt_nested_enum: -101
+`,
+	}, {
+		desc:  "proto3 enum not set",
+		input: &pb3.Enums{},
+		want:  "\n",
+	}, {
+		desc: "proto3 enum set to zero value",
+		input: &pb3.Enums{
+			SEnum:       pb3.Enum_ZERO,
+			SNestedEnum: pb3.Enums_CERO,
+		},
+		want: "\n",
+	}, {
+		desc: "proto3 enum",
+		input: &pb3.Enums{
+			SEnum:       pb3.Enum_ONE,
+			SNestedEnum: pb3.Enums_UNO,
+		},
+		want: `s_enum: ONE
+s_nested_enum: UNO
+`,
+	}, {
+		desc: "proto3 enum set to numeric values",
+		input: &pb3.Enums{
+			SEnum:       2,
+			SNestedEnum: 2,
+		},
+		want: `s_enum: TWO
+s_nested_enum: DOS
+`,
+	}, {
+		desc: "proto3 enum set to unnamed numeric values",
+		input: &pb3.Enums{
+			SEnum:       -47,
+			SNestedEnum: 47,
+		},
+		want: `s_enum: -47
+s_nested_enum: 47
+`,
+	}, {
+		desc:  "proto2 nested message not set",
+		input: &pb2.Nests{},
+		want:  "\n",
+	}, {
+		desc: "proto2 nested message set to empty",
+		input: &pb2.Nests{
+			OptNested: &pb2.Nested{},
+			Optgroup:  &pb2.Nests_OptGroup{},
+		},
+		want: `opt_nested: {}
+OptGroup: {}
+`,
+	}, {
+		desc: "proto2 nested messages",
+		input: &pb2.Nests{
+			OptNested: &pb2.Nested{
+				OptString: scalar.String("nested message"),
+				OptNested: &pb2.Nested{
+					OptString: scalar.String("another nested message"),
+				},
+			},
+		},
+		want: `opt_nested: {
+  opt_string: "nested message"
+  opt_nested: {
+    opt_string: "another nested message"
+  }
+}
+`,
+	}, {
+		desc: "proto2 groups",
+		input: &pb2.Nests{
+			Optgroup: &pb2.Nests_OptGroup{
+				OptString: scalar.String("inside a group"),
+				OptNested: &pb2.Nested{
+					OptString: scalar.String("nested message inside a group"),
+				},
+				Optnestedgroup: &pb2.Nests_OptGroup_OptNestedGroup{
+					OptFixed32: scalar.Uint32(47),
+				},
+			},
+		},
+		want: `OptGroup: {
+  opt_string: "inside a group"
+  opt_nested: {
+    opt_string: "nested message inside a group"
+  }
+  OptNestedGroup: {
+    opt_fixed32: 47
+  }
+}
+`,
+	}, {
+		desc:  "proto3 nested message not set",
+		input: &pb3.Nests{},
+		want:  "\n",
+	}, {
+		desc: "proto3 nested message set to empty",
+		input: &pb3.Nests{
+			SNested: &pb3.Nested{},
+		},
+		want: "s_nested: {}\n",
+	}, {
+		desc: "proto3 nested message",
+		input: &pb3.Nests{
+			SNested: &pb3.Nested{
+				SString: "nested message",
+				SNested: &pb3.Nested{
+					SString: "another nested message",
+				},
+			},
+		},
+		want: `s_nested: {
+  s_string: "nested message"
+  s_nested: {
+    s_string: "another nested message"
+  }
+}
+`,
+	}, {
+		desc: "proto3 nested message contains invalid UTF-8",
+		input: &pb3.Nests{
+			SNested: &pb3.Nested{
+				SString: "abc\xff",
+			},
+		},
+		want: `s_nested: {
+  s_string: "abc\xff"
+}
+`,
+		wantErr: true,
+	}, {
+		desc:  "oneof not set",
+		input: &pb3.Oneofs{},
+		want:  "\n",
+	}, {
+		desc: "oneof set to empty string",
+		input: &pb3.Oneofs{
+			Union: &pb3.Oneofs_OneofString{},
+		},
+		want: `oneof_string: ""
+`,
+	}, {
+		desc: "oneof set to string",
+		input: &pb3.Oneofs{
+			Union: &pb3.Oneofs_OneofString{
+				OneofString: "hello",
+			},
+		},
+		want: `oneof_string: "hello"
+`,
+	}, {
+		desc: "oneof set to enum",
+		input: &pb3.Oneofs{
+			Union: &pb3.Oneofs_OneofEnum{
+				OneofEnum: pb3.Enum_ZERO,
+			},
+		},
+		want: `oneof_enum: ZERO
+`,
+	}, {
+		desc: "oneof set to empty message",
+		input: &pb3.Oneofs{
+			Union: &pb3.Oneofs_OneofNested{
+				OneofNested: &pb3.Nested{},
+			},
+		},
+		want: "oneof_nested: {}\n",
+	}, {
+		desc: "oneof set to message",
+		input: &pb3.Oneofs{
+			Union: &pb3.Oneofs_OneofNested{
+				OneofNested: &pb3.Nested{
+					SString: "nested message",
+				},
+			},
+		},
+		want: `oneof_nested: {
+  s_string: "nested message"
+}
+`,
+	}, {
+		desc:  "repeated fields not set",
+		input: &pb2.Repeats{},
+		want:  "\n",
+	}, {
+		desc: "repeated fields set to empty slices",
+		input: &pb2.Repeats{
+			RptBool:   []bool{},
+			RptInt32:  []int32{},
+			RptInt64:  []int64{},
+			RptUint32: []uint32{},
+			RptUint64: []uint64{},
+			RptFloat:  []float32{},
+			RptDouble: []float64{},
+			RptBytes:  [][]byte{},
+		},
+		want: "\n",
+	}, {
+		desc: "repeated fields set to some values",
+		input: &pb2.Repeats{
+			RptBool:   []bool{true, false, true, true},
+			RptInt32:  []int32{1, 6, 0, 0},
+			RptInt64:  []int64{-64, 47},
+			RptUint32: []uint32{0xff, 0xffff},
+			RptUint64: []uint64{0xdeadbeef},
+			RptFloat:  []float32{float32(math.NaN()), float32(math.Inf(1)), float32(math.Inf(-1)), 1.034},
+			RptDouble: []float64{math.NaN(), math.Inf(1), math.Inf(-1), 1.23e-308},
+			RptString: []string{"hello", "世界"},
+			RptBytes: [][]byte{
+				[]byte("hello"),
+				[]byte("\xe4\xb8\x96\xe7\x95\x8c"),
+			},
+		},
+		want: `rpt_bool: true
+rpt_bool: false
+rpt_bool: true
+rpt_bool: true
+rpt_int32: 1
+rpt_int32: 6
+rpt_int32: 0
+rpt_int32: 0
+rpt_int64: -64
+rpt_int64: 47
+rpt_uint32: 255
+rpt_uint32: 65535
+rpt_uint64: 3735928559
+rpt_float: nan
+rpt_float: inf
+rpt_float: -inf
+rpt_float: 1.034
+rpt_double: nan
+rpt_double: inf
+rpt_double: -inf
+rpt_double: 1.23e-308
+rpt_string: "hello"
+rpt_string: "世界"
+rpt_bytes: "hello"
+rpt_bytes: "世界"
+`,
+	}, {
+		desc: "repeated contains invalid UTF-8",
+		input: &pb2.Repeats{
+			RptString: []string{"abc\xff"},
+		},
+		want: `rpt_string: "abc\xff"
+`,
+		wantErr: true,
+	}, {
+		desc: "repeated enums",
+		input: &pb2.Enums{
+			RptEnum:       []pb2.Enum{pb2.Enum_ONE, 2, pb2.Enum_TEN, 42},
+			RptNestedEnum: []pb2.Enums_NestedEnum{2, 47, 10},
+		},
+		want: `rpt_enum: ONE
+rpt_enum: TWO
+rpt_enum: TEN
+rpt_enum: 42
+rpt_nested_enum: DOS
+rpt_nested_enum: 47
+rpt_nested_enum: DIEZ
+`,
+	}, {
+		desc: "repeated messages set to empty",
+		input: &pb2.Nests{
+			RptNested: []*pb2.Nested{},
+			Rptgroup:  []*pb2.Nests_RptGroup{},
+		},
+		want: "\n",
+	}, {
+		desc: "repeated messages",
+		input: &pb2.Nests{
+			RptNested: []*pb2.Nested{
+				{
+					OptString: scalar.String("repeat nested one"),
+				},
+				{
+					OptString: scalar.String("repeat nested two"),
+					OptNested: &pb2.Nested{
+						OptString: scalar.String("inside repeat nested two"),
+					},
+				},
+				{},
+			},
+		},
+		want: `rpt_nested: {
+  opt_string: "repeat nested one"
+}
+rpt_nested: {
+  opt_string: "repeat nested two"
+  opt_nested: {
+    opt_string: "inside repeat nested two"
+  }
+}
+rpt_nested: {}
+`,
+	}, {
+		desc: "repeated messages contains nil value",
+		input: &pb2.Nests{
+			RptNested: []*pb2.Nested{nil, {}},
+		},
+		want: `rpt_nested: {}
+rpt_nested: {}
+`,
+	}, {
+		desc: "repeated groups",
+		input: &pb2.Nests{
+			Rptgroup: []*pb2.Nests_RptGroup{
+				{
+					RptString: []string{"hello", "world"},
+				},
+				{},
+				nil,
+			},
+		},
+		want: `RptGroup: {
+  rpt_string: "hello"
+  rpt_string: "world"
+}
+RptGroup: {}
+RptGroup: {}
+`,
+	}, {
+		desc:  "map fields not set",
+		input: &pb3.Maps{},
+		want:  "\n",
+	}, {
+		desc: "map fields set to empty",
+		input: &pb3.Maps{
+			Int32ToStr:   map[int32]string{},
+			BoolToUint32: map[bool]uint32{},
+			Uint64ToEnum: map[uint64]pb3.Enum{},
+			StrToNested:  map[string]*pb3.Nested{},
+			StrToOneofs:  map[string]*pb3.Oneofs{},
+		},
+		want: "\n",
+	}, {
+		desc: "map fields 1",
+		input: &pb3.Maps{
+			Int32ToStr: map[int32]string{
+				-101: "-101",
+				0xff: "0xff",
+				0:    "zero",
+			},
+			BoolToUint32: map[bool]uint32{
+				true:  42,
+				false: 101,
+			},
+		},
+		want: `int32_to_str: {
+  key: -101
+  value: "-101"
+}
+int32_to_str: {
+  key: 0
+  value: "zero"
+}
+int32_to_str: {
+  key: 255
+  value: "0xff"
+}
+bool_to_uint32: {
+  key: false
+  value: 101
+}
+bool_to_uint32: {
+  key: true
+  value: 42
+}
+`,
+	}, {
+		desc: "map fields 2",
+		input: &pb3.Maps{
+			Uint64ToEnum: map[uint64]pb3.Enum{
+				1:  pb3.Enum_ONE,
+				2:  pb3.Enum_TWO,
+				10: pb3.Enum_TEN,
+				47: 47,
+			},
+		},
+		want: `uint64_to_enum: {
+  key: 1
+  value: ONE
+}
+uint64_to_enum: {
+  key: 2
+  value: TWO
+}
+uint64_to_enum: {
+  key: 10
+  value: TEN
+}
+uint64_to_enum: {
+  key: 47
+  value: 47
+}
+`,
+	}, {
+		desc: "map fields 3",
+		input: &pb3.Maps{
+			StrToNested: map[string]*pb3.Nested{
+				"nested": &pb3.Nested{
+					SString: "nested in a map",
+				},
+			},
+		},
+		want: `str_to_nested: {
+  key: "nested"
+  value: {
+    s_string: "nested in a map"
+  }
+}
+`,
+	}, {
+		desc: "map fields 4",
+		input: &pb3.Maps{
+			StrToOneofs: map[string]*pb3.Oneofs{
+				"string": &pb3.Oneofs{
+					Union: &pb3.Oneofs_OneofString{
+						OneofString: "hello",
+					},
+				},
+				"nested": &pb3.Oneofs{
+					Union: &pb3.Oneofs_OneofNested{
+						OneofNested: &pb3.Nested{
+							SString: "nested oneof in map field value",
+						},
+					},
+				},
+			},
+		},
+		want: `str_to_oneofs: {
+  key: "nested"
+  value: {
+    oneof_nested: {
+      s_string: "nested oneof in map field value"
+    }
+  }
+}
+str_to_oneofs: {
+  key: "string"
+  value: {
+    oneof_string: "hello"
+  }
+}
+`,
+	}, {
+		desc: "map field value contains invalid UTF-8",
+		input: &pb3.Maps{
+			Int32ToStr: map[int32]string{
+				101: "abc\xff",
+			},
+		},
+		want: `int32_to_str: {
+  key: 101
+  value: "abc\xff"
+}
+`,
+		wantErr: true,
+	}, {
+		desc: "map field key contains invalid UTF-8",
+		input: &pb3.Maps{
+			StrToNested: map[string]*pb3.Nested{
+				"abc\xff": {},
+			},
+		},
+		want: `str_to_nested: {
+  key: "abc\xff"
+  value: {}
+}
+`,
+		wantErr: true,
+	}, {
+		desc: "map field contains nil value",
+		input: &pb3.Maps{
+			StrToNested: map[string]*pb3.Nested{
+				"nil": nil,
+			},
+		},
+		want: `str_to_nested: {
+  key: "nil"
+  value: {}
+}
+`,
+	}, {
+		desc:    "required fields not set",
+		input:   &pb2.Requireds{},
+		want:    "\n",
+		wantErr: true,
+	}, {
+		desc: "required fields partially set",
+		input: &pb2.Requireds{
+			ReqBool:     scalar.Bool(false),
+			ReqSfixed64: scalar.Int64(0xbeefcafe),
+			ReqDouble:   scalar.Float64(math.NaN()),
+			ReqString:   scalar.String("hello"),
+			ReqEnum:     pb2.Enum_ONE.Enum(),
+		},
+		want: `req_bool: false
+req_sfixed64: 3203386110
+req_double: nan
+req_string: "hello"
+req_enum: ONE
+`,
+		wantErr: true,
+	}, {
+		desc: "required fields not set with AllowPartial",
+		mo:   prototext.MarshalOptions{AllowPartial: true},
+		input: &pb2.Requireds{
+			ReqBool:     scalar.Bool(false),
+			ReqSfixed64: scalar.Int64(0xbeefcafe),
+			ReqDouble:   scalar.Float64(math.NaN()),
+			ReqString:   scalar.String("hello"),
+			ReqEnum:     pb2.Enum_ONE.Enum(),
+		},
+		want: `req_bool: false
+req_sfixed64: 3203386110
+req_double: nan
+req_string: "hello"
+req_enum: ONE
+`,
+	}, {
+		desc: "required fields all set",
+		input: &pb2.Requireds{
+			ReqBool:     scalar.Bool(false),
+			ReqSfixed64: scalar.Int64(0),
+			ReqDouble:   scalar.Float64(1.23),
+			ReqString:   scalar.String(""),
+			ReqEnum:     pb2.Enum_ONE.Enum(),
+			ReqNested:   &pb2.Nested{},
+		},
+		want: `req_bool: false
+req_sfixed64: 0
+req_double: 1.23
+req_string: ""
+req_enum: ONE
+req_nested: {}
+`,
+	}, {
+		desc: "indirect required field",
+		input: &pb2.IndirectRequired{
+			OptNested: &pb2.NestedWithRequired{},
+		},
+		want:    "opt_nested: {}\n",
+		wantErr: true,
+	}, {
+		desc: "indirect required field with AllowPartial",
+		mo:   prototext.MarshalOptions{AllowPartial: true},
+		input: &pb2.IndirectRequired{
+			OptNested: &pb2.NestedWithRequired{},
+		},
+		want: "opt_nested: {}\n",
+	}, {
+		desc: "indirect required field in empty repeated",
+		input: &pb2.IndirectRequired{
+			RptNested: []*pb2.NestedWithRequired{},
+		},
+		want: "\n",
+	}, {
+		desc: "indirect required field in repeated",
+		input: &pb2.IndirectRequired{
+			RptNested: []*pb2.NestedWithRequired{
+				&pb2.NestedWithRequired{},
+			},
+		},
+		want:    "rpt_nested: {}\n",
+		wantErr: true,
+	}, {
+		desc: "indirect required field in repeated with AllowPartial",
+		mo:   prototext.MarshalOptions{AllowPartial: true},
+		input: &pb2.IndirectRequired{
+			RptNested: []*pb2.NestedWithRequired{
+				&pb2.NestedWithRequired{},
+			},
+		},
+		want: "rpt_nested: {}\n",
+	}, {
+		desc: "indirect required field in empty map",
+		input: &pb2.IndirectRequired{
+			StrToNested: map[string]*pb2.NestedWithRequired{},
+		},
+		want: "\n",
+	}, {
+		desc: "indirect required field in map",
+		input: &pb2.IndirectRequired{
+			StrToNested: map[string]*pb2.NestedWithRequired{
+				"fail": &pb2.NestedWithRequired{},
+			},
+		},
+		want: `str_to_nested: {
+  key: "fail"
+  value: {}
+}
+`,
+		wantErr: true,
+	}, {
+		desc: "indirect required field in map with AllowPartial",
+		mo:   prototext.MarshalOptions{AllowPartial: true},
+		input: &pb2.IndirectRequired{
+			StrToNested: map[string]*pb2.NestedWithRequired{
+				"fail": &pb2.NestedWithRequired{},
+			},
+		},
+		want: `str_to_nested: {
+  key: "fail"
+  value: {}
+}
+`,
+	}, {
+		desc: "indirect required field in oneof",
+		input: &pb2.IndirectRequired{
+			Union: &pb2.IndirectRequired_OneofNested{
+				OneofNested: &pb2.NestedWithRequired{},
+			},
+		},
+		want:    "oneof_nested: {}\n",
+		wantErr: true,
+	}, {
+		desc: "indirect required field in oneof with AllowPartial",
+		mo:   prototext.MarshalOptions{AllowPartial: true},
+		input: &pb2.IndirectRequired{
+			Union: &pb2.IndirectRequired_OneofNested{
+				OneofNested: &pb2.NestedWithRequired{},
+			},
+		},
+		want: "oneof_nested: {}\n",
+	}, {
+		desc: "unknown varint and fixed types",
+		input: &pb2.Scalars{
+			OptString: scalar.String("this message contains unknown fields"),
+			XXX_unrecognized: pack.Message{
+				pack.Tag{101, pack.VarintType}, pack.Bool(true),
+				pack.Tag{102, pack.VarintType}, pack.Varint(0xff),
+				pack.Tag{103, pack.Fixed32Type}, pack.Uint32(47),
+				pack.Tag{104, pack.Fixed64Type}, pack.Int64(0xdeadbeef),
+			}.Marshal(),
+		},
+		want: `opt_string: "this message contains unknown fields"
+101: 1
+102: 255
+103: 47
+104: 3735928559
+`,
+	}, {
+		desc: "unknown length-delimited",
+		input: &pb2.Scalars{
+			XXX_unrecognized: pack.Message{
+				pack.Tag{101, pack.BytesType}, pack.LengthPrefix{pack.Bool(true), pack.Bool(false)},
+				pack.Tag{102, pack.BytesType}, pack.String("hello world"),
+				pack.Tag{103, pack.BytesType}, pack.Bytes("\xe4\xb8\x96\xe7\x95\x8c"),
+			}.Marshal(),
+		},
+		want: `101: "\x01\x00"
+102: "hello world"
+103: "世界"
+`,
+	}, {
+		desc: "unknown group type",
+		input: &pb2.Scalars{
+			XXX_unrecognized: pack.Message{
+				pack.Tag{101, pack.StartGroupType}, pack.Tag{101, pack.EndGroupType},
+				pack.Tag{102, pack.StartGroupType},
+				pack.Tag{101, pack.VarintType}, pack.Bool(false),
+				pack.Tag{102, pack.BytesType}, pack.String("inside a group"),
+				pack.Tag{102, pack.EndGroupType},
+			}.Marshal(),
+		},
+		want: `101: {}
+102: {
+  101: 0
+  102: "inside a group"
+}
+`,
+	}, {
+		desc: "unknown unpack repeated field",
+		input: &pb2.Scalars{
+			XXX_unrecognized: pack.Message{
+				pack.Tag{101, pack.BytesType}, pack.LengthPrefix{pack.Bool(true), pack.Bool(false), pack.Bool(true)},
+				pack.Tag{102, pack.BytesType}, pack.String("hello"),
+				pack.Tag{101, pack.VarintType}, pack.Bool(true),
+				pack.Tag{102, pack.BytesType}, pack.String("世界"),
+			}.Marshal(),
+		},
+		want: `101: "\x01\x00\x01"
+101: 1
+102: "hello"
+102: "世界"
+`,
+	}, {
+		desc: "extensions of non-repeated fields",
+		input: func() proto.Message {
+			m := &pb2.Extensions{
+				OptString: scalar.String("non-extension field"),
+				OptBool:   scalar.Bool(true),
+				OptInt32:  scalar.Int32(42),
+			}
+			setExtension(m, pb2.E_OptExtBool, true)
+			setExtension(m, pb2.E_OptExtString, "extension field")
+			setExtension(m, pb2.E_OptExtEnum, pb2.Enum_TEN)
+			setExtension(m, pb2.E_OptExtNested, &pb2.Nested{
+				OptString: scalar.String("nested in an extension"),
+				OptNested: &pb2.Nested{
+					OptString: scalar.String("another nested in an extension"),
+				},
+			})
+			return m
+		}(),
+		want: `opt_string: "non-extension field"
+opt_bool: true
+opt_int32: 42
+[pb2.opt_ext_bool]: true
+[pb2.opt_ext_enum]: TEN
+[pb2.opt_ext_nested]: {
+  opt_string: "nested in an extension"
+  opt_nested: {
+    opt_string: "another nested in an extension"
+  }
+}
+[pb2.opt_ext_string]: "extension field"
+`,
+	}, {
+		desc: "extension field contains invalid UTF-8",
+		input: func() proto.Message {
+			m := &pb2.Extensions{}
+			setExtension(m, pb2.E_OptExtString, "abc\xff")
+			return m
+		}(),
+		want: `[pb2.opt_ext_string]: "abc\xff"
+`,
+		wantErr: true,
+	}, {
+		desc: "extension partial returns error",
+		input: func() proto.Message {
+			m := &pb2.Extensions{}
+			setExtension(m, pb2.E_OptExtPartial, &pb2.PartialRequired{
+				OptString: scalar.String("partial1"),
+			})
+			setExtension(m, pb2.E_ExtensionsContainer_OptExtPartial, &pb2.PartialRequired{
+				OptString: scalar.String("partial2"),
+			})
+			return m
+		}(),
+		want: `[pb2.ExtensionsContainer.opt_ext_partial]: {
+  opt_string: "partial2"
+}
+[pb2.opt_ext_partial]: {
+  opt_string: "partial1"
+}
+`,
+		wantErr: true,
+	}, {
+		desc: "extension partial with AllowPartial",
+		mo:   prototext.MarshalOptions{AllowPartial: true},
+		input: func() proto.Message {
+			m := &pb2.Extensions{}
+			setExtension(m, pb2.E_OptExtPartial, &pb2.PartialRequired{
+				OptString: scalar.String("partial1"),
+			})
+			return m
+		}(),
+		want: `[pb2.opt_ext_partial]: {
+  opt_string: "partial1"
+}
+`,
+	}, {
+		desc: "extension message field set to nil",
+		input: func() proto.Message {
+			m := &pb2.Extensions{}
+			setExtension(m, pb2.E_OptExtNested, nil)
+			return m
+		}(),
+		want: "\n",
+	}, {
+		desc: "extensions of repeated fields",
+		input: func() proto.Message {
+			m := &pb2.Extensions{}
+			setExtension(m, pb2.E_RptExtEnum, &[]pb2.Enum{pb2.Enum_TEN, 101, pb2.Enum_ONE})
+			setExtension(m, pb2.E_RptExtFixed32, &[]uint32{42, 47})
+			setExtension(m, pb2.E_RptExtNested, &[]*pb2.Nested{
+				&pb2.Nested{OptString: scalar.String("one")},
+				&pb2.Nested{OptString: scalar.String("two")},
+				&pb2.Nested{OptString: scalar.String("three")},
+			})
+			return m
+		}(),
+		want: `[pb2.rpt_ext_enum]: TEN
+[pb2.rpt_ext_enum]: 101
+[pb2.rpt_ext_enum]: ONE
+[pb2.rpt_ext_fixed32]: 42
+[pb2.rpt_ext_fixed32]: 47
+[pb2.rpt_ext_nested]: {
+  opt_string: "one"
+}
+[pb2.rpt_ext_nested]: {
+  opt_string: "two"
+}
+[pb2.rpt_ext_nested]: {
+  opt_string: "three"
+}
+`,
+	}, {
+		desc: "extensions of non-repeated fields in another message",
+		input: func() proto.Message {
+			m := &pb2.Extensions{}
+			setExtension(m, pb2.E_ExtensionsContainer_OptExtBool, true)
+			setExtension(m, pb2.E_ExtensionsContainer_OptExtString, "extension field")
+			setExtension(m, pb2.E_ExtensionsContainer_OptExtEnum, pb2.Enum_TEN)
+			setExtension(m, pb2.E_ExtensionsContainer_OptExtNested, &pb2.Nested{
+				OptString: scalar.String("nested in an extension"),
+				OptNested: &pb2.Nested{
+					OptString: scalar.String("another nested in an extension"),
+				},
+			})
+			return m
+		}(),
+		want: `[pb2.ExtensionsContainer.opt_ext_bool]: true
+[pb2.ExtensionsContainer.opt_ext_enum]: TEN
+[pb2.ExtensionsContainer.opt_ext_nested]: {
+  opt_string: "nested in an extension"
+  opt_nested: {
+    opt_string: "another nested in an extension"
+  }
+}
+[pb2.ExtensionsContainer.opt_ext_string]: "extension field"
+`,
+	}, {
+		desc: "extensions of repeated fields in another message",
+		input: func() proto.Message {
+			m := &pb2.Extensions{
+				OptString: scalar.String("non-extension field"),
+				OptBool:   scalar.Bool(true),
+				OptInt32:  scalar.Int32(42),
+			}
+			setExtension(m, pb2.E_ExtensionsContainer_RptExtEnum, &[]pb2.Enum{pb2.Enum_TEN, 101, pb2.Enum_ONE})
+			setExtension(m, pb2.E_ExtensionsContainer_RptExtString, &[]string{"hello", "world"})
+			setExtension(m, pb2.E_ExtensionsContainer_RptExtNested, &[]*pb2.Nested{
+				&pb2.Nested{OptString: scalar.String("one")},
+				&pb2.Nested{OptString: scalar.String("two")},
+				&pb2.Nested{OptString: scalar.String("three")},
+			})
+			return m
+		}(),
+		want: `opt_string: "non-extension field"
+opt_bool: true
+opt_int32: 42
+[pb2.ExtensionsContainer.rpt_ext_enum]: TEN
+[pb2.ExtensionsContainer.rpt_ext_enum]: 101
+[pb2.ExtensionsContainer.rpt_ext_enum]: ONE
+[pb2.ExtensionsContainer.rpt_ext_nested]: {
+  opt_string: "one"
+}
+[pb2.ExtensionsContainer.rpt_ext_nested]: {
+  opt_string: "two"
+}
+[pb2.ExtensionsContainer.rpt_ext_nested]: {
+  opt_string: "three"
+}
+[pb2.ExtensionsContainer.rpt_ext_string]: "hello"
+[pb2.ExtensionsContainer.rpt_ext_string]: "world"
+`,
+	}, {
+		desc: "MessageSet",
+		input: func() proto.Message {
+			m := &pb2.MessageSet{}
+			setExtension(m, pb2.E_MessageSetExtension_MessageSetExtension, &pb2.MessageSetExtension{
+				OptString: scalar.String("a messageset extension"),
+			})
+			setExtension(m, pb2.E_MessageSetExtension_NotMessageSetExtension, &pb2.MessageSetExtension{
+				OptString: scalar.String("not a messageset extension"),
+			})
+			setExtension(m, pb2.E_MessageSetExtension_ExtNested, &pb2.Nested{
+				OptString: scalar.String("just a regular extension"),
+			})
+			return m
+		}(),
+		want: `[pb2.MessageSetExtension]: {
+  opt_string: "a messageset extension"
+}
+[pb2.MessageSetExtension.ext_nested]: {
+  opt_string: "just a regular extension"
+}
+[pb2.MessageSetExtension.not_message_set_extension]: {
+  opt_string: "not a messageset extension"
+}
+`,
+	}, {
+		desc: "not real MessageSet 1",
+		input: func() proto.Message {
+			m := &pb2.FakeMessageSet{}
+			setExtension(m, pb2.E_FakeMessageSetExtension_MessageSetExtension, &pb2.FakeMessageSetExtension{
+				OptString: scalar.String("not a messageset extension"),
+			})
+			return m
+		}(),
+		want: `[pb2.FakeMessageSetExtension.message_set_extension]: {
+  opt_string: "not a messageset extension"
+}
+`,
+	}, {
+		desc: "not real MessageSet 2",
+		input: func() proto.Message {
+			m := &pb2.MessageSet{}
+			setExtension(m, pb2.E_MessageSetExtension, &pb2.FakeMessageSetExtension{
+				OptString: scalar.String("another not a messageset extension"),
+			})
+			return m
+		}(),
+		want: `[pb2.message_set_extension]: {
+  opt_string: "another not a messageset extension"
+}
+`,
+	}, {
+		desc: "Any not expanded",
+		mo: prototext.MarshalOptions{
+			Resolver: preg.NewTypes(),
+		},
+		input: func() proto.Message {
+			m := &pb2.Nested{
+				OptString: scalar.String("embedded inside Any"),
+				OptNested: &pb2.Nested{
+					OptString: scalar.String("inception"),
+				},
+			}
+			b, err := proto.MarshalOptions{Deterministic: true}.Marshal(m)
+			if err != nil {
+				t.Fatalf("error in binary marshaling message for Any.value: %v", err)
+			}
+			return &knownpb.Any{
+				TypeUrl: "pb2.Nested",
+				Value:   b,
+			}
+		}(),
+		want: `type_url: "pb2.Nested"
+value: "\n\x13embedded inside Any\x12\x0b\n\tinception"
+`,
+	}, {
+		desc: "Any expanded",
+		mo: prototext.MarshalOptions{
+			Resolver: preg.NewTypes(pimpl.Export{}.MessageTypeOf(&pb2.Nested{})),
+		},
+		input: func() proto.Message {
+			m := &pb2.Nested{
+				OptString: scalar.String("embedded inside Any"),
+				OptNested: &pb2.Nested{
+					OptString: scalar.String("inception"),
+				},
+			}
+			b, err := proto.MarshalOptions{Deterministic: true}.Marshal(m)
+			if err != nil {
+				t.Fatalf("error in binary marshaling message for Any.value: %v", err)
+			}
+			return &knownpb.Any{
+				TypeUrl: "foo/pb2.Nested",
+				Value:   b,
+			}
+		}(),
+		want: `[foo/pb2.Nested]: {
+  opt_string: "embedded inside Any"
+  opt_nested: {
+    opt_string: "inception"
+  }
+}
+`,
+	}, {
+		desc: "Any expanded with missing required error",
+		mo: prototext.MarshalOptions{
+			Resolver: preg.NewTypes(pimpl.Export{}.MessageTypeOf(&pb2.PartialRequired{})),
+		},
+		input: func() proto.Message {
+			m := &pb2.PartialRequired{
+				OptString: scalar.String("embedded inside Any"),
+			}
+			b, err := proto.MarshalOptions{
+				AllowPartial:  true,
+				Deterministic: true,
+			}.Marshal(m)
+			if err != nil {
+				t.Fatalf("error in binary marshaling message for Any.value: %v", err)
+			}
+			return &knownpb.Any{
+				TypeUrl: string(m.ProtoReflect().Descriptor().FullName()),
+				Value:   b,
+			}
+		}(),
+		want: `[pb2.PartialRequired]: {
+  opt_string: "embedded inside Any"
+}
+`,
+		wantErr: true,
+	}, {
+		desc: "Any with invalid UTF-8",
+		mo: prototext.MarshalOptions{
+			Resolver: preg.NewTypes(pimpl.Export{}.MessageTypeOf(&pb3.Nested{})),
+		},
+		input: func() proto.Message {
+			m := &pb3.Nested{
+				SString: "abcd",
+			}
+			b, err := proto.MarshalOptions{Deterministic: true}.Marshal(m)
+			if err != nil {
+				t.Fatalf("error in binary marshaling message for Any.value: %v", err)
+			}
+			return &knownpb.Any{
+				TypeUrl: string(m.ProtoReflect().Descriptor().FullName()),
+				Value:   bytes.Replace(b, []byte("abcd"), []byte("abc\xff"), -1),
+			}
+		}(),
+		want: `[pb3.Nested]: {
+  s_string: "abc\xff"
+}
+`,
+		wantErr: true,
+	}, {
+		desc: "Any with invalid value",
+		mo: prototext.MarshalOptions{
+			Resolver: preg.NewTypes(pimpl.Export{}.MessageTypeOf(&pb2.Nested{})),
+		},
+		input: &knownpb.Any{
+			TypeUrl: "foo/pb2.Nested",
+			Value:   dhex("80"),
+		},
+		want: `type_url: "foo/pb2.Nested"
+value: "\x80"
+`,
+	}}
+
+	for _, tt := range tests {
+		tt := tt
+		t.Run(tt.desc, func(t *testing.T) {
+			// Use 2-space indentation on all MarshalOptions.
+			tt.mo.Indent = "  "
+			b, err := tt.mo.Marshal(tt.input)
+			if err != nil && !tt.wantErr {
+				t.Errorf("Marshal() returned error: %v\n", err)
+			}
+			if err == nil && tt.wantErr {
+				t.Error("Marshal() got nil error, want error\n")
+			}
+			got := string(b)
+			if tt.want != "" && got != tt.want {
+				t.Errorf("Marshal()\n<got>\n%v\n<want>\n%v\n", got, tt.want)
+				if diff := cmp.Diff(tt.want, got, splitLines); diff != "" {
+					t.Errorf("Marshal() diff -want +got\n%v\n", diff)
+				}
+			}
+		})
+	}
+}