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/protojson/encode_test.go b/encoding/protojson/encode_test.go
new file mode 100644
index 0000000..c652118
--- /dev/null
+++ b/encoding/protojson/encode_test.go
@@ -0,0 +1,1975 @@
+// Copyright 2019 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 protojson_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/protojson"
+	"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"
+)
+
+// 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      protojson.MarshalOptions
+		input   proto.Message
+		want    string
+		wantErr bool // TODO: Verify error message substring.
+	}{{
+		desc:  "proto2 optional scalars not set",
+		input: &pb2.Scalars{},
+		want:  "{}",
+	}, {
+		desc:  "proto3 scalars not set",
+		input: &pb3.Scalars{},
+		want:  "{}",
+	}, {
+		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: `{
+  "optBool": false,
+  "optInt32": 0,
+  "optInt64": "0",
+  "optUint32": 0,
+  "optUint64": "0",
+  "optSint32": 0,
+  "optSint64": "0",
+  "optFixed32": 0,
+  "optFixed64": "0",
+  "optSfixed32": 0,
+  "optSfixed64": "0",
+  "optFloat": 0,
+  "optDouble": 0,
+  "optBytes": "",
+  "optString": ""
+}`,
+	}, {
+		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(1.234),
+			OptBytes:    []byte("谷歌"),
+			OptString:   scalar.String("谷歌"),
+		},
+		want: `{
+  "optBool": true,
+  "optInt32": 255,
+  "optInt64": "3735928559",
+  "optUint32": 47,
+  "optUint64": "3735928559",
+  "optSint32": -1001,
+  "optSint64": "-65535",
+  "optFixed64": "64",
+  "optSfixed32": -32,
+  "optFloat": 1.02,
+  "optDouble": 1.234,
+  "optBytes": "6LC35q2M",
+  "optString": "谷歌"
+}`,
+	}, {
+		desc: "string",
+		input: &pb3.Scalars{
+			SString: "谷歌",
+		},
+		want: `{
+  "sString": "谷歌"
+}`,
+	}, {
+		desc: "string with invalid UTF8",
+		input: &pb3.Scalars{
+			SString: "abc\xff",
+		},
+		want:    "{\n  \"sString\": \"abc\xff\"\n}",
+		wantErr: true,
+	}, {
+		desc: "float nan",
+		input: &pb3.Scalars{
+			SFloat: float32(math.NaN()),
+		},
+		want: `{
+  "sFloat": "NaN"
+}`,
+	}, {
+		desc: "float positive infinity",
+		input: &pb3.Scalars{
+			SFloat: float32(math.Inf(1)),
+		},
+		want: `{
+  "sFloat": "Infinity"
+}`,
+	}, {
+		desc: "float negative infinity",
+		input: &pb3.Scalars{
+			SFloat: float32(math.Inf(-1)),
+		},
+		want: `{
+  "sFloat": "-Infinity"
+}`,
+	}, {
+		desc: "double nan",
+		input: &pb3.Scalars{
+			SDouble: math.NaN(),
+		},
+		want: `{
+  "sDouble": "NaN"
+}`,
+	}, {
+		desc: "double positive infinity",
+		input: &pb3.Scalars{
+			SDouble: math.Inf(1),
+		},
+		want: `{
+  "sDouble": "Infinity"
+}`,
+	}, {
+		desc: "double negative infinity",
+		input: &pb3.Scalars{
+			SDouble: math.Inf(-1),
+		},
+		want: `{
+  "sDouble": "-Infinity"
+}`,
+	}, {
+		desc:  "proto2 enum not set",
+		input: &pb2.Enums{},
+		want:  "{}",
+	}, {
+		desc: "proto2 enum set to zero value",
+		input: &pb2.Enums{
+			OptEnum:       pb2Enum(0),
+			OptNestedEnum: pb2Enums_NestedEnum(0),
+		},
+		want: `{
+  "optEnum": 0,
+  "optNestedEnum": 0
+}`,
+	}, {
+		desc: "proto2 enum",
+		input: &pb2.Enums{
+			OptEnum:       pb2.Enum_ONE.Enum(),
+			OptNestedEnum: pb2.Enums_UNO.Enum(),
+		},
+		want: `{
+  "optEnum": "ONE",
+  "optNestedEnum": "UNO"
+}`,
+	}, {
+		desc: "proto2 enum set to numeric values",
+		input: &pb2.Enums{
+			OptEnum:       pb2Enum(2),
+			OptNestedEnum: pb2Enums_NestedEnum(2),
+		},
+		want: `{
+  "optEnum": "TWO",
+  "optNestedEnum": "DOS"
+}`,
+	}, {
+		desc: "proto2 enum set to unnamed numeric values",
+		input: &pb2.Enums{
+			OptEnum:       pb2Enum(101),
+			OptNestedEnum: pb2Enums_NestedEnum(-101),
+		},
+		want: `{
+  "optEnum": 101,
+  "optNestedEnum": -101
+}`,
+	}, {
+		desc:  "proto3 enum not set",
+		input: &pb3.Enums{},
+		want:  "{}",
+	}, {
+		desc: "proto3 enum set to zero value",
+		input: &pb3.Enums{
+			SEnum:       pb3.Enum_ZERO,
+			SNestedEnum: pb3.Enums_CERO,
+		},
+		want: "{}",
+	}, {
+		desc: "proto3 enum",
+		input: &pb3.Enums{
+			SEnum:       pb3.Enum_ONE,
+			SNestedEnum: pb3.Enums_UNO,
+		},
+		want: `{
+  "sEnum": "ONE",
+  "sNestedEnum": "UNO"
+}`,
+	}, {
+		desc: "proto3 enum set to numeric values",
+		input: &pb3.Enums{
+			SEnum:       2,
+			SNestedEnum: 2,
+		},
+		want: `{
+  "sEnum": "TWO",
+  "sNestedEnum": "DOS"
+}`,
+	}, {
+		desc: "proto3 enum set to unnamed numeric values",
+		input: &pb3.Enums{
+			SEnum:       -47,
+			SNestedEnum: 47,
+		},
+		want: `{
+  "sEnum": -47,
+  "sNestedEnum": 47
+}`,
+	}, {
+		desc:  "proto2 nested message not set",
+		input: &pb2.Nests{},
+		want:  "{}",
+	}, {
+		desc: "proto2 nested message set to empty",
+		input: &pb2.Nests{
+			OptNested: &pb2.Nested{},
+			Optgroup:  &pb2.Nests_OptGroup{},
+		},
+		want: `{
+  "optNested": {},
+  "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: `{
+  "optNested": {
+    "optString": "nested message",
+    "optNested": {
+      "optString": "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": {
+    "optString": "inside a group",
+    "optNested": {
+      "optString": "nested message inside a group"
+    },
+    "optnestedgroup": {
+      "optFixed32": 47
+    }
+  }
+}`,
+	}, {
+		desc:  "proto3 nested message not set",
+		input: &pb3.Nests{},
+		want:  "{}",
+	}, {
+		desc: "proto3 nested message set to empty",
+		input: &pb3.Nests{
+			SNested: &pb3.Nested{},
+		},
+		want: `{
+  "sNested": {}
+}`,
+	}, {
+		desc: "proto3 nested message",
+		input: &pb3.Nests{
+			SNested: &pb3.Nested{
+				SString: "nested message",
+				SNested: &pb3.Nested{
+					SString: "another nested message",
+				},
+			},
+		},
+		want: `{
+  "sNested": {
+    "sString": "nested message",
+    "sNested": {
+      "sString": "another nested message"
+    }
+  }
+}`,
+	}, {
+		desc:  "oneof not set",
+		input: &pb3.Oneofs{},
+		want:  "{}",
+	}, {
+		desc: "oneof set to empty string",
+		input: &pb3.Oneofs{
+			Union: &pb3.Oneofs_OneofString{},
+		},
+		want: `{
+  "oneofString": ""
+}`,
+	}, {
+		desc: "oneof set to string",
+		input: &pb3.Oneofs{
+			Union: &pb3.Oneofs_OneofString{
+				OneofString: "hello",
+			},
+		},
+		want: `{
+  "oneofString": "hello"
+}`,
+	}, {
+		desc: "oneof set to enum",
+		input: &pb3.Oneofs{
+			Union: &pb3.Oneofs_OneofEnum{
+				OneofEnum: pb3.Enum_ZERO,
+			},
+		},
+		want: `{
+  "oneofEnum": "ZERO"
+}`,
+	}, {
+		desc: "oneof set to empty message",
+		input: &pb3.Oneofs{
+			Union: &pb3.Oneofs_OneofNested{
+				OneofNested: &pb3.Nested{},
+			},
+		},
+		want: `{
+  "oneofNested": {}
+}`,
+	}, {
+		desc: "oneof set to message",
+		input: &pb3.Oneofs{
+			Union: &pb3.Oneofs_OneofNested{
+				OneofNested: &pb3.Nested{
+					SString: "nested message",
+				},
+			},
+		},
+		want: `{
+  "oneofNested": {
+    "sString": "nested message"
+  }
+}`,
+	}, {
+		desc:  "repeated fields not set",
+		input: &pb2.Repeats{},
+		want:  "{}",
+	}, {
+		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: "{}",
+	}, {
+		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: `{
+  "rptBool": [
+    true,
+    false,
+    true,
+    true
+  ],
+  "rptInt32": [
+    1,
+    6,
+    0,
+    0
+  ],
+  "rptInt64": [
+    "-64",
+    "47"
+  ],
+  "rptUint32": [
+    255,
+    65535
+  ],
+  "rptUint64": [
+    "3735928559"
+  ],
+  "rptFloat": [
+    "NaN",
+    "Infinity",
+    "-Infinity",
+    1.034
+  ],
+  "rptDouble": [
+    "NaN",
+    "Infinity",
+    "-Infinity",
+    1.23e-308
+  ],
+  "rptString": [
+    "hello",
+    "世界"
+  ],
+  "rptBytes": [
+    "aGVsbG8=",
+    "5LiW55WM"
+  ]
+}`,
+	}, {
+		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: `{
+  "rptEnum": [
+    "ONE",
+    "TWO",
+    "TEN",
+    42
+  ],
+  "rptNestedEnum": [
+    "DOS",
+    47,
+    "DIEZ"
+  ]
+}`,
+	}, {
+		desc: "repeated messages set to empty",
+		input: &pb2.Nests{
+			RptNested: []*pb2.Nested{},
+			Rptgroup:  []*pb2.Nests_RptGroup{},
+		},
+		want: "{}",
+	}, {
+		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: `{
+  "rptNested": [
+    {
+      "optString": "repeat nested one"
+    },
+    {
+      "optString": "repeat nested two",
+      "optNested": {
+        "optString": "inside repeat nested two"
+      }
+    },
+    {}
+  ]
+}`,
+	}, {
+		desc: "repeated messages contains nil value",
+		input: &pb2.Nests{
+			RptNested: []*pb2.Nested{nil, {}},
+		},
+		want: `{
+  "rptNested": [
+    {},
+    {}
+  ]
+}`,
+	}, {
+		desc: "repeated groups",
+		input: &pb2.Nests{
+			Rptgroup: []*pb2.Nests_RptGroup{
+				{
+					RptString: []string{"hello", "world"},
+				},
+				{},
+				nil,
+			},
+		},
+		want: `{
+  "rptgroup": [
+    {
+      "rptString": [
+        "hello",
+        "world"
+      ]
+    },
+    {},
+    {}
+  ]
+}`,
+	}, {
+		desc:  "map fields not set",
+		input: &pb3.Maps{},
+		want:  "{}",
+	}, {
+		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: "{}",
+	}, {
+		desc: "map fields 1",
+		input: &pb3.Maps{
+			BoolToUint32: map[bool]uint32{
+				true:  42,
+				false: 101,
+			},
+		},
+		want: `{
+  "boolToUint32": {
+    "false": 101,
+    "true": 42
+  }
+}`,
+	}, {
+		desc: "map fields 2",
+		input: &pb3.Maps{
+			Int32ToStr: map[int32]string{
+				-101: "-101",
+				0xff: "0xff",
+				0:    "zero",
+			},
+		},
+		want: `{
+  "int32ToStr": {
+    "-101": "-101",
+    "0": "zero",
+    "255": "0xff"
+  }
+}`,
+	}, {
+		desc: "map fields 3",
+		input: &pb3.Maps{
+			Uint64ToEnum: map[uint64]pb3.Enum{
+				1:  pb3.Enum_ONE,
+				2:  pb3.Enum_TWO,
+				10: pb3.Enum_TEN,
+				47: 47,
+			},
+		},
+		want: `{
+  "uint64ToEnum": {
+    "1": "ONE",
+    "2": "TWO",
+    "10": "TEN",
+    "47": 47
+  }
+}`,
+	}, {
+		desc: "map fields 4",
+		input: &pb3.Maps{
+			StrToNested: map[string]*pb3.Nested{
+				"nested": &pb3.Nested{
+					SString: "nested in a map",
+				},
+			},
+		},
+		want: `{
+  "strToNested": {
+    "nested": {
+      "sString": "nested in a map"
+    }
+  }
+}`,
+	}, {
+		desc: "map fields 5",
+		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: `{
+  "strToOneofs": {
+    "nested": {
+      "oneofNested": {
+        "sString": "nested oneof in map field value"
+      }
+    },
+    "string": {
+      "oneofString": "hello"
+    }
+  }
+}`,
+	}, {
+		desc: "map field contains nil value",
+		input: &pb3.Maps{
+			StrToNested: map[string]*pb3.Nested{
+				"nil": nil,
+			},
+		},
+		want: `{
+  "strToNested": {
+    "nil": {}
+  }
+}`,
+	}, {
+		desc:    "required fields not set",
+		input:   &pb2.Requireds{},
+		want:    `{}`,
+		wantErr: true,
+	}, {
+		desc: "required fields partially set",
+		input: &pb2.Requireds{
+			ReqBool:     scalar.Bool(false),
+			ReqSfixed64: scalar.Int64(0),
+			ReqDouble:   scalar.Float64(1.23),
+			ReqString:   scalar.String("hello"),
+			ReqEnum:     pb2.Enum_ONE.Enum(),
+		},
+		want: `{
+  "reqBool": false,
+  "reqSfixed64": "0",
+  "reqDouble": 1.23,
+  "reqString": "hello",
+  "reqEnum": "ONE"
+}`,
+		wantErr: true,
+	}, {
+		desc: "required fields not set with AllowPartial",
+		mo:   protojson.MarshalOptions{AllowPartial: true},
+		input: &pb2.Requireds{
+			ReqBool:     scalar.Bool(false),
+			ReqSfixed64: scalar.Int64(0),
+			ReqDouble:   scalar.Float64(1.23),
+			ReqString:   scalar.String("hello"),
+			ReqEnum:     pb2.Enum_ONE.Enum(),
+		},
+		want: `{
+  "reqBool": false,
+  "reqSfixed64": "0",
+  "reqDouble": 1.23,
+  "reqString": "hello",
+  "reqEnum": "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("hello"),
+			ReqEnum:     pb2.Enum_ONE.Enum(),
+			ReqNested:   &pb2.Nested{},
+		},
+		want: `{
+  "reqBool": false,
+  "reqSfixed64": "0",
+  "reqDouble": 1.23,
+  "reqString": "hello",
+  "reqEnum": "ONE",
+  "reqNested": {}
+}`,
+	}, {
+		desc: "indirect required field",
+		input: &pb2.IndirectRequired{
+			OptNested: &pb2.NestedWithRequired{},
+		},
+		want: `{
+  "optNested": {}
+}`,
+		wantErr: true,
+	}, {
+		desc: "indirect required field with AllowPartial",
+		mo:   protojson.MarshalOptions{AllowPartial: true},
+		input: &pb2.IndirectRequired{
+			OptNested: &pb2.NestedWithRequired{},
+		},
+		want: `{
+  "optNested": {}
+}`,
+	}, {
+		desc: "indirect required field in empty repeated",
+		input: &pb2.IndirectRequired{
+			RptNested: []*pb2.NestedWithRequired{},
+		},
+		want: `{}`,
+	}, {
+		desc: "indirect required field in repeated",
+		input: &pb2.IndirectRequired{
+			RptNested: []*pb2.NestedWithRequired{
+				&pb2.NestedWithRequired{},
+			},
+		},
+		want: `{
+  "rptNested": [
+    {}
+  ]
+}`,
+		wantErr: true,
+	}, {
+		desc: "indirect required field in repeated with AllowPartial",
+		mo:   protojson.MarshalOptions{AllowPartial: true},
+		input: &pb2.IndirectRequired{
+			RptNested: []*pb2.NestedWithRequired{
+				&pb2.NestedWithRequired{},
+			},
+		},
+		want: `{
+  "rptNested": [
+    {}
+  ]
+}`,
+	}, {
+		desc: "indirect required field in empty map",
+		input: &pb2.IndirectRequired{
+			StrToNested: map[string]*pb2.NestedWithRequired{},
+		},
+		want: "{}",
+	}, {
+		desc: "indirect required field in map",
+		input: &pb2.IndirectRequired{
+			StrToNested: map[string]*pb2.NestedWithRequired{
+				"fail": &pb2.NestedWithRequired{},
+			},
+		},
+		want: `{
+  "strToNested": {
+    "fail": {}
+  }
+}`,
+		wantErr: true,
+	}, {
+		desc: "indirect required field in map with AllowPartial",
+		mo:   protojson.MarshalOptions{AllowPartial: true},
+		input: &pb2.IndirectRequired{
+			StrToNested: map[string]*pb2.NestedWithRequired{
+				"fail": &pb2.NestedWithRequired{},
+			},
+		},
+		want: `{
+  "strToNested": {
+    "fail": {}
+  }
+}`,
+	}, {
+		desc: "indirect required field in oneof",
+		input: &pb2.IndirectRequired{
+			Union: &pb2.IndirectRequired_OneofNested{
+				OneofNested: &pb2.NestedWithRequired{},
+			},
+		},
+		want: `{
+  "oneofNested": {}
+}`,
+		wantErr: true,
+	}, {
+		desc: "indirect required field in oneof with AllowPartial",
+		mo:   protojson.MarshalOptions{AllowPartial: true},
+		input: &pb2.IndirectRequired{
+			Union: &pb2.IndirectRequired_OneofNested{
+				OneofNested: &pb2.NestedWithRequired{},
+			},
+		},
+		want: `{
+  "oneofNested": {}
+}`,
+	}, {
+		desc: "unknown fields are ignored",
+		input: &pb2.Scalars{
+			OptString: scalar.String("no unknowns"),
+			XXX_unrecognized: pack.Message{
+				pack.Tag{101, pack.BytesType}, pack.String("hello world"),
+			}.Marshal(),
+		},
+		want: `{
+  "optString": "no unknowns"
+}`,
+	}, {
+		desc: "json_name",
+		input: &pb3.JSONNames{
+			SString: "json_name",
+		},
+		want: `{
+  "foo_bar": "json_name"
+}`,
+	}, {
+		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: `{
+  "optString": "non-extension field",
+  "optBool": true,
+  "optInt32": 42,
+  "[pb2.opt_ext_bool]": true,
+  "[pb2.opt_ext_enum]": "TEN",
+  "[pb2.opt_ext_nested]": {
+    "optString": "nested in an extension",
+    "optNested": {
+      "optString": "another nested in an extension"
+    }
+  },
+  "[pb2.opt_ext_string]": "extension field"
+}`,
+	}, {
+		desc: "extension message field set to nil",
+		input: func() proto.Message {
+			m := &pb2.Extensions{}
+			setExtension(m, pb2.E_OptExtNested, nil)
+			return m
+		}(),
+		want: "{}",
+	}, {
+		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",
+    101,
+    "ONE"
+  ],
+  "[pb2.rpt_ext_fixed32]": [
+    42,
+    47
+  ],
+  "[pb2.rpt_ext_nested]": [
+    {
+      "optString": "one"
+    },
+    {
+      "optString": "two"
+    },
+    {
+      "optString": "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]": {
+    "optString": "nested in an extension",
+    "optNested": {
+      "optString": "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: `{
+  "optString": "non-extension field",
+  "optBool": true,
+  "optInt32": 42,
+  "[pb2.ExtensionsContainer.rpt_ext_enum]": [
+    "TEN",
+    101,
+    "ONE"
+  ],
+  "[pb2.ExtensionsContainer.rpt_ext_nested]": [
+    {
+      "optString": "one"
+    },
+    {
+      "optString": "two"
+    },
+    {
+      "optString": "three"
+    }
+  ],
+  "[pb2.ExtensionsContainer.rpt_ext_string]": [
+    "hello",
+    "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]": {
+    "optString": "a messageset extension"
+  },
+  "[pb2.MessageSetExtension.ext_nested]": {
+    "optString": "just a regular extension"
+  },
+  "[pb2.MessageSetExtension.not_message_set_extension]": {
+    "optString": "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]": {
+    "optString": "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]": {
+    "optString": "another not a messageset extension"
+  }
+}`,
+	}, {
+		desc:  "BoolValue empty",
+		input: &knownpb.BoolValue{},
+		want:  `false`,
+	}, {
+		desc:  "BoolValue",
+		input: &knownpb.BoolValue{Value: true},
+		want:  `true`,
+	}, {
+		desc:  "Int32Value empty",
+		input: &knownpb.Int32Value{},
+		want:  `0`,
+	}, {
+		desc:  "Int32Value",
+		input: &knownpb.Int32Value{Value: 42},
+		want:  `42`,
+	}, {
+		desc:  "Int64Value",
+		input: &knownpb.Int64Value{Value: 42},
+		want:  `"42"`,
+	}, {
+		desc:  "UInt32Value",
+		input: &knownpb.UInt32Value{Value: 42},
+		want:  `42`,
+	}, {
+		desc:  "UInt64Value",
+		input: &knownpb.UInt64Value{Value: 42},
+		want:  `"42"`,
+	}, {
+		desc:  "FloatValue",
+		input: &knownpb.FloatValue{Value: 1.02},
+		want:  `1.02`,
+	}, {
+		desc:  "FloatValue Infinity",
+		input: &knownpb.FloatValue{Value: float32(math.Inf(-1))},
+		want:  `"-Infinity"`,
+	}, {
+		desc:  "DoubleValue",
+		input: &knownpb.DoubleValue{Value: 1.02},
+		want:  `1.02`,
+	}, {
+		desc:  "DoubleValue NaN",
+		input: &knownpb.DoubleValue{Value: math.NaN()},
+		want:  `"NaN"`,
+	}, {
+		desc:  "StringValue empty",
+		input: &knownpb.StringValue{},
+		want:  `""`,
+	}, {
+		desc:  "StringValue",
+		input: &knownpb.StringValue{Value: "谷歌"},
+		want:  `"谷歌"`,
+	}, {
+		desc:    "StringValue with invalid UTF8 error",
+		input:   &knownpb.StringValue{Value: "abc\xff"},
+		want:    "\"abc\xff\"",
+		wantErr: true,
+	}, {
+		desc: "StringValue field with invalid UTF8 error",
+		input: &pb2.KnownTypes{
+			OptString: &knownpb.StringValue{Value: "abc\xff"},
+		},
+		want:    "{\n  \"optString\": \"abc\xff\"\n}",
+		wantErr: true,
+	}, {
+		desc:  "BytesValue",
+		input: &knownpb.BytesValue{Value: []byte("hello")},
+		want:  `"aGVsbG8="`,
+	}, {
+		desc:  "Empty",
+		input: &knownpb.Empty{},
+		want:  `{}`,
+	}, {
+		desc:  "NullValue field",
+		input: &pb2.KnownTypes{OptNull: new(knownpb.NullValue)},
+		want: `{
+  "optNull": null
+}`,
+	}, {
+		desc:    "Value empty",
+		input:   &knownpb.Value{},
+		wantErr: true,
+	}, {
+		desc: "Value empty field",
+		input: &pb2.KnownTypes{
+			OptValue: &knownpb.Value{},
+		},
+		wantErr: true,
+	}, {
+		desc:  "Value contains NullValue",
+		input: &knownpb.Value{Kind: &knownpb.Value_NullValue{}},
+		want:  `null`,
+	}, {
+		desc:  "Value contains BoolValue",
+		input: &knownpb.Value{Kind: &knownpb.Value_BoolValue{}},
+		want:  `false`,
+	}, {
+		desc:  "Value contains NumberValue",
+		input: &knownpb.Value{Kind: &knownpb.Value_NumberValue{1.02}},
+		want:  `1.02`,
+	}, {
+		desc:  "Value contains StringValue",
+		input: &knownpb.Value{Kind: &knownpb.Value_StringValue{"hello"}},
+		want:  `"hello"`,
+	}, {
+		desc:    "Value contains StringValue with invalid UTF8",
+		input:   &knownpb.Value{Kind: &knownpb.Value_StringValue{"\xff"}},
+		want:    "\"\xff\"",
+		wantErr: true,
+	}, {
+		desc: "Value contains Struct",
+		input: &knownpb.Value{
+			Kind: &knownpb.Value_StructValue{
+				&knownpb.Struct{
+					Fields: map[string]*knownpb.Value{
+						"null":   {Kind: &knownpb.Value_NullValue{}},
+						"number": {Kind: &knownpb.Value_NumberValue{}},
+						"string": {Kind: &knownpb.Value_StringValue{}},
+						"struct": {Kind: &knownpb.Value_StructValue{}},
+						"list":   {Kind: &knownpb.Value_ListValue{}},
+						"bool":   {Kind: &knownpb.Value_BoolValue{}},
+					},
+				},
+			},
+		},
+		want: `{
+  "bool": false,
+  "list": [],
+  "null": null,
+  "number": 0,
+  "string": "",
+  "struct": {}
+}`,
+	}, {
+		desc: "Value contains ListValue",
+		input: &knownpb.Value{
+			Kind: &knownpb.Value_ListValue{
+				&knownpb.ListValue{
+					Values: []*knownpb.Value{
+						{Kind: &knownpb.Value_BoolValue{}},
+						{Kind: &knownpb.Value_NullValue{}},
+						{Kind: &knownpb.Value_NumberValue{}},
+						{Kind: &knownpb.Value_StringValue{}},
+						{Kind: &knownpb.Value_StructValue{}},
+						{Kind: &knownpb.Value_ListValue{}},
+					},
+				},
+			},
+		},
+		want: `[
+  false,
+  null,
+  0,
+  "",
+  {},
+  []
+]`,
+	}, {
+		desc:  "Struct with nil map",
+		input: &knownpb.Struct{},
+		want:  `{}`,
+	}, {
+		desc: "Struct with empty map",
+		input: &knownpb.Struct{
+			Fields: map[string]*knownpb.Value{},
+		},
+		want: `{}`,
+	}, {
+		desc: "Struct",
+		input: &knownpb.Struct{
+			Fields: map[string]*knownpb.Value{
+				"bool":   {Kind: &knownpb.Value_BoolValue{true}},
+				"null":   {Kind: &knownpb.Value_NullValue{}},
+				"number": {Kind: &knownpb.Value_NumberValue{3.1415}},
+				"string": {Kind: &knownpb.Value_StringValue{"hello"}},
+				"struct": {
+					Kind: &knownpb.Value_StructValue{
+						&knownpb.Struct{
+							Fields: map[string]*knownpb.Value{
+								"string": {Kind: &knownpb.Value_StringValue{"world"}},
+							},
+						},
+					},
+				},
+				"list": {
+					Kind: &knownpb.Value_ListValue{
+						&knownpb.ListValue{
+							Values: []*knownpb.Value{
+								{Kind: &knownpb.Value_BoolValue{}},
+								{Kind: &knownpb.Value_NullValue{}},
+								{Kind: &knownpb.Value_NumberValue{}},
+							},
+						},
+					},
+				},
+			},
+		},
+		want: `{
+  "bool": true,
+  "list": [
+    false,
+    null,
+    0
+  ],
+  "null": null,
+  "number": 3.1415,
+  "string": "hello",
+  "struct": {
+    "string": "world"
+  }
+}`,
+	}, {
+		desc: "Struct message with invalid UTF8 string",
+		input: &knownpb.Struct{
+			Fields: map[string]*knownpb.Value{
+				"string": {Kind: &knownpb.Value_StringValue{"\xff"}},
+			},
+		},
+		want:    "{\n  \"string\": \"\xff\"\n}",
+		wantErr: true,
+	}, {
+		desc:  "ListValue with nil values",
+		input: &knownpb.ListValue{},
+		want:  `[]`,
+	}, {
+		desc: "ListValue with empty values",
+		input: &knownpb.ListValue{
+			Values: []*knownpb.Value{},
+		},
+		want: `[]`,
+	}, {
+		desc: "ListValue",
+		input: &knownpb.ListValue{
+			Values: []*knownpb.Value{
+				{Kind: &knownpb.Value_BoolValue{true}},
+				{Kind: &knownpb.Value_NullValue{}},
+				{Kind: &knownpb.Value_NumberValue{3.1415}},
+				{Kind: &knownpb.Value_StringValue{"hello"}},
+				{
+					Kind: &knownpb.Value_ListValue{
+						&knownpb.ListValue{
+							Values: []*knownpb.Value{
+								{Kind: &knownpb.Value_BoolValue{}},
+								{Kind: &knownpb.Value_NullValue{}},
+								{Kind: &knownpb.Value_NumberValue{}},
+							},
+						},
+					},
+				},
+				{
+					Kind: &knownpb.Value_StructValue{
+						&knownpb.Struct{
+							Fields: map[string]*knownpb.Value{
+								"string": {Kind: &knownpb.Value_StringValue{"world"}},
+							},
+						},
+					},
+				},
+			},
+		},
+		want: `[
+  true,
+  null,
+  3.1415,
+  "hello",
+  [
+    false,
+    null,
+    0
+  ],
+  {
+    "string": "world"
+  }
+]`,
+	}, {
+		desc: "ListValue with invalid UTF8 string",
+		input: &knownpb.ListValue{
+			Values: []*knownpb.Value{
+				{Kind: &knownpb.Value_StringValue{"\xff"}},
+			},
+		},
+		want:    "[\n  \"\xff\"\n]",
+		wantErr: true,
+	}, {
+		desc:  "Duration empty",
+		input: &knownpb.Duration{},
+		want:  `"0s"`,
+	}, {
+		desc:  "Duration with secs",
+		input: &knownpb.Duration{Seconds: 3},
+		want:  `"3s"`,
+	}, {
+		desc:  "Duration with -secs",
+		input: &knownpb.Duration{Seconds: -3},
+		want:  `"-3s"`,
+	}, {
+		desc:  "Duration with nanos",
+		input: &knownpb.Duration{Nanos: 1e6},
+		want:  `"0.001s"`,
+	}, {
+		desc:  "Duration with -nanos",
+		input: &knownpb.Duration{Nanos: -1e6},
+		want:  `"-0.001s"`,
+	}, {
+		desc:  "Duration with large secs",
+		input: &knownpb.Duration{Seconds: 1e10, Nanos: 1},
+		want:  `"10000000000.000000001s"`,
+	}, {
+		desc:  "Duration with 6-digit nanos",
+		input: &knownpb.Duration{Nanos: 1e4},
+		want:  `"0.000010s"`,
+	}, {
+		desc:  "Duration with 3-digit nanos",
+		input: &knownpb.Duration{Nanos: 1e6},
+		want:  `"0.001s"`,
+	}, {
+		desc:  "Duration with -secs -nanos",
+		input: &knownpb.Duration{Seconds: -123, Nanos: -450},
+		want:  `"-123.000000450s"`,
+	}, {
+		desc:  "Duration max value",
+		input: &knownpb.Duration{Seconds: 315576000000, Nanos: 999999999},
+		want:  `"315576000000.999999999s"`,
+	}, {
+		desc:  "Duration min value",
+		input: &knownpb.Duration{Seconds: -315576000000, Nanos: -999999999},
+		want:  `"-315576000000.999999999s"`,
+	}, {
+		desc:    "Duration with +secs -nanos",
+		input:   &knownpb.Duration{Seconds: 1, Nanos: -1},
+		wantErr: true,
+	}, {
+		desc:    "Duration with -secs +nanos",
+		input:   &knownpb.Duration{Seconds: -1, Nanos: 1},
+		wantErr: true,
+	}, {
+		desc:    "Duration with +secs out of range",
+		input:   &knownpb.Duration{Seconds: 315576000001},
+		wantErr: true,
+	}, {
+		desc:    "Duration with -secs out of range",
+		input:   &knownpb.Duration{Seconds: -315576000001},
+		wantErr: true,
+	}, {
+		desc:    "Duration with +nanos out of range",
+		input:   &knownpb.Duration{Seconds: 0, Nanos: 1e9},
+		wantErr: true,
+	}, {
+		desc:    "Duration with -nanos out of range",
+		input:   &knownpb.Duration{Seconds: 0, Nanos: -1e9},
+		wantErr: true,
+	}, {
+		desc:  "Timestamp zero",
+		input: &knownpb.Timestamp{},
+		want:  `"1970-01-01T00:00:00Z"`,
+	}, {
+		desc:  "Timestamp",
+		input: &knownpb.Timestamp{Seconds: 1553036601},
+		want:  `"2019-03-19T23:03:21Z"`,
+	}, {
+		desc:  "Timestamp with nanos",
+		input: &knownpb.Timestamp{Seconds: 1553036601, Nanos: 1},
+		want:  `"2019-03-19T23:03:21.000000001Z"`,
+	}, {
+		desc:  "Timestamp with 6-digit nanos",
+		input: &knownpb.Timestamp{Nanos: 1e3},
+		want:  `"1970-01-01T00:00:00.000001Z"`,
+	}, {
+		desc:  "Timestamp with 3-digit nanos",
+		input: &knownpb.Timestamp{Nanos: 1e7},
+		want:  `"1970-01-01T00:00:00.010Z"`,
+	}, {
+		desc:  "Timestamp max value",
+		input: &knownpb.Timestamp{Seconds: 253402300799, Nanos: 999999999},
+		want:  `"9999-12-31T23:59:59.999999999Z"`,
+	}, {
+		desc:  "Timestamp min value",
+		input: &knownpb.Timestamp{Seconds: -62135596800},
+		want:  `"0001-01-01T00:00:00Z"`,
+	}, {
+		desc:    "Timestamp with +secs out of range",
+		input:   &knownpb.Timestamp{Seconds: 253402300800},
+		wantErr: true,
+	}, {
+		desc:    "Timestamp with -secs out of range",
+		input:   &knownpb.Timestamp{Seconds: -62135596801},
+		wantErr: true,
+	}, {
+		desc:    "Timestamp with -nanos",
+		input:   &knownpb.Timestamp{Nanos: -1},
+		wantErr: true,
+	}, {
+		desc:    "Timestamp with +nanos out of range",
+		input:   &knownpb.Timestamp{Nanos: 1e9},
+		wantErr: true,
+	}, {
+		desc:  "FieldMask empty",
+		input: &knownpb.FieldMask{},
+		want:  `""`,
+	}, {
+		desc: "FieldMask",
+		input: &knownpb.FieldMask{
+			Paths: []string{
+				"foo",
+				"foo_bar",
+				"foo.bar_qux",
+				"_foo",
+			},
+		},
+		want: `"foo,fooBar,foo.barQux,Foo"`,
+	}, {
+		desc: "FieldMask error 1",
+		input: &knownpb.FieldMask{
+			Paths: []string{"foo_"},
+		},
+		wantErr: true,
+	}, {
+		desc: "FieldMask error 2",
+		input: &knownpb.FieldMask{
+			Paths: []string{"foo__bar"},
+		},
+		wantErr: true,
+	}, {
+		desc:  "Any empty",
+		input: &knownpb.Any{},
+		want:  `{}`,
+	}, {
+		desc: "Any with non-custom message",
+		mo: protojson.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: `{
+  "@type": "foo/pb2.Nested",
+  "optString": "embedded inside Any",
+  "optNested": {
+    "optString": "inception"
+  }
+}`,
+	}, {
+		desc: "Any with empty embedded message",
+		mo: protojson.MarshalOptions{
+			Resolver: preg.NewTypes(pimpl.Export{}.MessageTypeOf(&pb2.Nested{})),
+		},
+		input: &knownpb.Any{TypeUrl: "foo/pb2.Nested"},
+		want: `{
+  "@type": "foo/pb2.Nested"
+}`,
+	}, {
+		desc:    "Any without registered type",
+		mo:      protojson.MarshalOptions{Resolver: preg.NewTypes()},
+		input:   &knownpb.Any{TypeUrl: "foo/pb2.Nested"},
+		wantErr: true,
+	}, {
+		desc: "Any with missing required error",
+		mo: protojson.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: `{
+  "@type": "pb2.PartialRequired",
+  "optString": "embedded inside Any"
+}`,
+		wantErr: true,
+	}, {
+		desc: "Any with partial required and AllowPartial",
+		mo: protojson.MarshalOptions{
+			AllowPartial: true,
+			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: `{
+  "@type": "pb2.PartialRequired",
+  "optString": "embedded inside Any"
+}`,
+	}, {
+		desc: "Any with invalid UTF8",
+		mo: protojson.MarshalOptions{
+			Resolver: preg.NewTypes(pimpl.Export{}.MessageTypeOf(&pb2.Nested{})),
+		},
+		input: func() proto.Message {
+			m := &pb2.Nested{
+				OptString: scalar.String("abc\xff"),
+			}
+			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: `{
+  "@type": "foo/pb2.Nested",
+  "optString": "` + "abc\xff" + `"
+}`,
+		wantErr: true,
+	}, {
+		desc: "Any with invalid value",
+		mo: protojson.MarshalOptions{
+			Resolver: preg.NewTypes(pimpl.Export{}.MessageTypeOf(&pb2.Nested{})),
+		},
+		input: &knownpb.Any{
+			TypeUrl: "foo/pb2.Nested",
+			Value:   dhex("80"),
+		},
+		wantErr: true,
+	}, {
+		desc: "Any with BoolValue",
+		mo: protojson.MarshalOptions{
+			Resolver: preg.NewTypes(pimpl.Export{}.MessageTypeOf(&knownpb.BoolValue{})),
+		},
+		input: func() proto.Message {
+			m := &knownpb.BoolValue{Value: true}
+			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: "type.googleapis.com/google.protobuf.BoolValue",
+				Value:   b,
+			}
+		}(),
+		want: `{
+  "@type": "type.googleapis.com/google.protobuf.BoolValue",
+  "value": true
+}`,
+	}, {
+		desc: "Any with Empty",
+		mo: protojson.MarshalOptions{
+			Resolver: preg.NewTypes(pimpl.Export{}.MessageTypeOf(&knownpb.Empty{})),
+		},
+		input: func() proto.Message {
+			m := &knownpb.Empty{}
+			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: "type.googleapis.com/google.protobuf.Empty",
+				Value:   b,
+			}
+		}(),
+		want: `{
+  "@type": "type.googleapis.com/google.protobuf.Empty",
+  "value": {}
+}`,
+	}, {
+		desc: "Any with StringValue containing invalid UTF8",
+		mo: protojson.MarshalOptions{
+			Resolver: preg.NewTypes(pimpl.Export{}.MessageTypeOf(&knownpb.StringValue{})),
+		},
+		input: func() proto.Message {
+			m := &knownpb.StringValue{Value: "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: "google.protobuf.StringValue",
+				Value:   bytes.Replace(b, []byte("abcd"), []byte("abc\xff"), -1),
+			}
+		}(),
+		want: `{
+  "@type": "google.protobuf.StringValue",
+  "value": "` + "abc\xff" + `"
+}`,
+		wantErr: true,
+	}, {
+		desc: "Any with Int64Value",
+		mo: protojson.MarshalOptions{
+			Resolver: preg.NewTypes(pimpl.Export{}.MessageTypeOf(&knownpb.Int64Value{})),
+		},
+		input: func() proto.Message {
+			m := &knownpb.Int64Value{Value: 42}
+			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: "google.protobuf.Int64Value",
+				Value:   b,
+			}
+		}(),
+		want: `{
+  "@type": "google.protobuf.Int64Value",
+  "value": "42"
+}`,
+	}, {
+		desc: "Any with Duration",
+		mo: protojson.MarshalOptions{
+			Resolver: preg.NewTypes(pimpl.Export{}.MessageTypeOf(&knownpb.Duration{})),
+		},
+		input: func() proto.Message {
+			m := &knownpb.Duration{}
+			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: "type.googleapis.com/google.protobuf.Duration",
+				Value:   b,
+			}
+		}(),
+		want: `{
+  "@type": "type.googleapis.com/google.protobuf.Duration",
+  "value": "0s"
+}`,
+	}, {
+		desc: "Any with empty Value",
+		mo: protojson.MarshalOptions{
+			Resolver: preg.NewTypes(pimpl.Export{}.MessageTypeOf(&knownpb.Value{})),
+		},
+		input: func() proto.Message {
+			m := &knownpb.Value{}
+			b, err := proto.Marshal(m)
+			if err != nil {
+				t.Fatalf("error in binary marshaling message for Any.value: %v", err)
+			}
+			return &knownpb.Any{
+				TypeUrl: "type.googleapis.com/google.protobuf.Value",
+				Value:   b,
+			}
+		}(),
+		wantErr: true,
+	}, {
+		desc: "Any with Value of StringValue",
+		mo: protojson.MarshalOptions{
+			Resolver: preg.NewTypes(pimpl.Export{}.MessageTypeOf(&knownpb.Value{})),
+		},
+		input: func() proto.Message {
+			m := &knownpb.Value{Kind: &knownpb.Value_StringValue{"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: "type.googleapis.com/google.protobuf.Value",
+				Value:   bytes.Replace(b, []byte("abcd"), []byte("abc\xff"), -1),
+			}
+		}(),
+		want: `{
+  "@type": "type.googleapis.com/google.protobuf.Value",
+  "value": "` + "abc\xff" + `"
+}`,
+		wantErr: true,
+	}, {
+		desc: "Any with Value of NullValue",
+		mo: protojson.MarshalOptions{
+			Resolver: preg.NewTypes(pimpl.Export{}.MessageTypeOf(&knownpb.Value{})),
+		},
+		input: func() proto.Message {
+			m := &knownpb.Value{Kind: &knownpb.Value_NullValue{}}
+			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: "type.googleapis.com/google.protobuf.Value",
+				Value:   b,
+			}
+		}(),
+		want: `{
+  "@type": "type.googleapis.com/google.protobuf.Value",
+  "value": null
+}`,
+	}, {
+		desc: "Any with Struct",
+		mo: protojson.MarshalOptions{
+			Resolver: preg.NewTypes(
+				pimpl.Export{}.MessageTypeOf(&knownpb.Struct{}),
+				pimpl.Export{}.MessageTypeOf(&knownpb.Value{}),
+				pimpl.Export{}.MessageTypeOf(&knownpb.BoolValue{}),
+				pimpl.Export{}.EnumTypeOf(knownpb.NullValue_NULL_VALUE),
+				pimpl.Export{}.MessageTypeOf(&knownpb.StringValue{}),
+			),
+		},
+		input: func() proto.Message {
+			m := &knownpb.Struct{
+				Fields: map[string]*knownpb.Value{
+					"bool":   {Kind: &knownpb.Value_BoolValue{true}},
+					"null":   {Kind: &knownpb.Value_NullValue{}},
+					"string": {Kind: &knownpb.Value_StringValue{"hello"}},
+					"struct": {
+						Kind: &knownpb.Value_StructValue{
+							&knownpb.Struct{
+								Fields: map[string]*knownpb.Value{
+									"string": {Kind: &knownpb.Value_StringValue{"world"}},
+								},
+							},
+						},
+					},
+				},
+			}
+			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: "google.protobuf.Struct",
+				Value:   b,
+			}
+		}(),
+		want: `{
+  "@type": "google.protobuf.Struct",
+  "value": {
+    "bool": true,
+    "null": null,
+    "string": "hello",
+    "struct": {
+      "string": "world"
+    }
+  }
+}`,
+	}, {
+		desc: "Any with missing type_url",
+		mo: protojson.MarshalOptions{
+			Resolver: preg.NewTypes(pimpl.Export{}.MessageTypeOf(&knownpb.BoolValue{})),
+		},
+		input: func() proto.Message {
+			m := &knownpb.BoolValue{Value: true}
+			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{
+				Value: b,
+			}
+		}(),
+		wantErr: true,
+	}, {
+		desc: "well known types as field values",
+		mo: protojson.MarshalOptions{
+			Resolver: preg.NewTypes(pimpl.Export{}.MessageTypeOf(&knownpb.Empty{})),
+		},
+		input: &pb2.KnownTypes{
+			OptBool:      &knownpb.BoolValue{Value: false},
+			OptInt32:     &knownpb.Int32Value{Value: 42},
+			OptInt64:     &knownpb.Int64Value{Value: 42},
+			OptUint32:    &knownpb.UInt32Value{Value: 42},
+			OptUint64:    &knownpb.UInt64Value{Value: 42},
+			OptFloat:     &knownpb.FloatValue{Value: 1.23},
+			OptDouble:    &knownpb.DoubleValue{Value: 3.1415},
+			OptString:    &knownpb.StringValue{Value: "hello"},
+			OptBytes:     &knownpb.BytesValue{Value: []byte("hello")},
+			OptDuration:  &knownpb.Duration{Seconds: 123},
+			OptTimestamp: &knownpb.Timestamp{Seconds: 1553036601},
+			OptStruct: &knownpb.Struct{
+				Fields: map[string]*knownpb.Value{
+					"string": {Kind: &knownpb.Value_StringValue{"hello"}},
+				},
+			},
+			OptList: &knownpb.ListValue{
+				Values: []*knownpb.Value{
+					{Kind: &knownpb.Value_NullValue{}},
+					{Kind: &knownpb.Value_StringValue{}},
+					{Kind: &knownpb.Value_StructValue{}},
+					{Kind: &knownpb.Value_ListValue{}},
+				},
+			},
+			OptValue: &knownpb.Value{
+				Kind: &knownpb.Value_StringValue{"world"},
+			},
+			OptEmpty: &knownpb.Empty{},
+			OptAny: &knownpb.Any{
+				TypeUrl: "google.protobuf.Empty",
+			},
+			OptFieldmask: &knownpb.FieldMask{
+				Paths: []string{"foo_bar", "bar_foo"},
+			},
+		},
+		want: `{
+  "optBool": false,
+  "optInt32": 42,
+  "optInt64": "42",
+  "optUint32": 42,
+  "optUint64": "42",
+  "optFloat": 1.23,
+  "optDouble": 3.1415,
+  "optString": "hello",
+  "optBytes": "aGVsbG8=",
+  "optDuration": "123s",
+  "optTimestamp": "2019-03-19T23:03:21Z",
+  "optStruct": {
+    "string": "hello"
+  },
+  "optList": [
+    null,
+    "",
+    {},
+    []
+  ],
+  "optValue": "world",
+  "optEmpty": {},
+  "optAny": {
+    "@type": "google.protobuf.Empty",
+    "value": {}
+  },
+  "optFieldmask": "fooBar,barFoo"
+}`,
+	}}
+
+	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.Errorf("Marshal() got nil error, want error\n")
+			}
+			got := string(b)
+			if 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)
+				}
+			}
+		})
+	}
+}