8 files changed, 167 insertions, 34 deletions

diff --git a/src/pkg/encoding/json/Makefile b/src/pkg/encoding/json/Makefile
deleted file mode 100644
index 37223e75e..000000000
--- a/src/pkg/encoding/json/Makefile
+++ /dev/null
@@ -1,16 +0,0 @@
-# Copyright 2009 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.
-
-include ../../../Make.inc
-
-TARG=encoding/json
-GOFILES=\
-	decode.go\
-	encode.go\
-	indent.go\
-	scanner.go\
-	stream.go\
-	tags.go\
-
-include ../../../Make.pkg
diff --git a/src/pkg/encoding/json/decode.go b/src/pkg/encoding/json/decode.go
index 87076b53d..110c6fd62 100644
--- a/src/pkg/encoding/json/decode.go
+++ b/src/pkg/encoding/json/decode.go
@@ -496,6 +496,12 @@ func (d *decodeState) object(v reflect.Value) {
 					// Pretend this field doesn't exist.
 					continue
 				}
+				if sf.Anonymous {
+					// Pretend this field doesn't exist,
+					// so that we can do a good job with
+					// these in a later version.
+					continue
+				}
 				// First, tag match
 				tagName, _ := parseTag(tag)
 				if tagName == key {
@@ -963,3 +969,11 @@ func unquoteBytes(s []byte) (t []byte, ok bool) {
 	}
 	return b[0:w], true
 }
+
+// The following is issue 3069.
+
+// BUG(rsc): This package ignores anonymous (embedded) struct fields
+// during encoding and decoding.  A future version may assign meaning
+// to them.  To force an anonymous field to be ignored in all future
+// versions of this package, use an explicit `json:"-"` tag in the struct
+// definition.
diff --git a/src/pkg/encoding/json/decode_test.go b/src/pkg/encoding/json/decode_test.go
index cc3103f03..0eec586a9 100644
--- a/src/pkg/encoding/json/decode_test.go
+++ b/src/pkg/encoding/json/decode_test.go
@@ -598,3 +598,53 @@ var pallValueIndent = `{
 }`
 
 var pallValueCompact = strings.Map(noSpace, pallValueIndent)
+
+func TestRefUnmarshal(t *testing.T) {
+	type S struct {
+		// Ref is defined in encode_test.go.
+		R0 Ref
+		R1 *Ref
+	}
+	want := S{
+		R0: 12,
+		R1: new(Ref),
+	}
+	*want.R1 = 12
+
+	var got S
+	if err := Unmarshal([]byte(`{"R0":"ref","R1":"ref"}`), &got); err != nil {
+		t.Fatalf("Unmarshal: %v", err)
+	}
+	if !reflect.DeepEqual(got, want) {
+		t.Errorf("got %+v, want %+v", got, want)
+	}
+}
+
+// Test that anonymous fields are ignored.
+// We may assign meaning to them later.
+func TestAnonymous(t *testing.T) {
+	type S struct {
+		T
+		N int
+	}
+
+	data, err := Marshal(new(S))
+	if err != nil {
+		t.Fatalf("Marshal: %v", err)
+	}
+	want := `{"N":0}`
+	if string(data) != want {
+		t.Fatalf("Marshal = %#q, want %#q", string(data), want)
+	}
+
+	var s S
+	if err := Unmarshal([]byte(`{"T": 1, "T": {"Y": 1}, "N": 2}`), &s); err != nil {
+		t.Fatalf("Unmarshal: %v", err)
+	}
+	if s.N != 2 {
+		t.Fatal("Unmarshal: did not set N")
+	}
+	if s.T.Y != 0 {
+		t.Fatal("Unmarshal: did set T.Y")
+	}
+}
diff --git a/src/pkg/encoding/json/encode.go b/src/pkg/encoding/json/encode.go
index eac14a47e..8a794b79b 100644
--- a/src/pkg/encoding/json/encode.go
+++ b/src/pkg/encoding/json/encode.go
@@ -262,8 +262,18 @@ func (e *encodeState) reflectValueQuoted(v reflect.Value, quoted bool) {
 		return
 	}
 
-	if j, ok := v.Interface().(Marshaler); ok && (v.Kind() != reflect.Ptr || !v.IsNil()) {
-		b, err := j.MarshalJSON()
+	m, ok := v.Interface().(Marshaler)
+	if !ok {
+		// T doesn't match the interface. Check against *T too.
+		if v.Kind() != reflect.Ptr && v.CanAddr() {
+			m, ok = v.Addr().Interface().(Marshaler)
+			if ok {
+				v = v.Addr()
+			}
+		}
+	}
+	if ok && (v.Kind() != reflect.Ptr || !v.IsNil()) {
+		b, err := m.MarshalJSON()
 		if err == nil {
 			// copy JSON into buffer, checking validity.
 			err = Compact(&e.Buffer, b)
@@ -528,6 +538,11 @@ func encodeFields(t reflect.Type) []encodeField {
 		if f.PkgPath != "" {
 			continue
 		}
+		if f.Anonymous {
+			// We want to do a better job with these later,
+			// so for now pretend they don't exist.
+			continue
+		}
 		var ef encodeField
 		ef.i = i
 		ef.tag = f.Name
diff --git a/src/pkg/encoding/json/encode_test.go b/src/pkg/encoding/json/encode_test.go
index 0e39559a4..7a726a91c 100644
--- a/src/pkg/encoding/json/encode_test.go
+++ b/src/pkg/encoding/json/encode_test.go
@@ -126,3 +126,44 @@ func TestUnsupportedValues(t *testing.T) {
 		}
 	}
 }
+
+// Ref has Marshaler and Unmarshaler methods with pointer receiver.
+type Ref int
+
+func (*Ref) MarshalJSON() ([]byte, error) {
+	return []byte(`"ref"`), nil
+}
+
+func (r *Ref) UnmarshalJSON([]byte) error {
+	*r = 12
+	return nil
+}
+
+// Val has Marshaler methods with value receiver.
+type Val int
+
+func (Val) MarshalJSON() ([]byte, error) {
+	return []byte(`"val"`), nil
+}
+
+func TestRefValMarshal(t *testing.T) {
+	var s = struct {
+		R0 Ref
+		R1 *Ref
+		V0 Val
+		V1 *Val
+	}{
+		R0: 12,
+		R1: new(Ref),
+		V0: 13,
+		V1: new(Val),
+	}
+	const want = `{"R0":"ref","R1":"ref","V0":"val","V1":"val"}`
+	b, err := Marshal(&s)
+	if err != nil {
+		t.Fatalf("Marshal: %v", err)
+	}
+	if got := string(b); got != want {
+		t.Errorf("got %q, want %q", got, want)
+	}
+}
diff --git a/src/pkg/encoding/json/example_test.go b/src/pkg/encoding/json/example_test.go
index 7f4a78c31..b8d150eda 100644
--- a/src/pkg/encoding/json/example_test.go
+++ b/src/pkg/encoding/json/example_test.go
@@ -7,10 +7,12 @@ package json_test
 import (
 	"encoding/json"
 	"fmt"
+	"io"
+	"log"
 	"os"
+	"strings"
 )
 
-// {"ID":1,"Name":"Reds","Colors":["Crimson","Red","Ruby","Maroon"]}
 func ExampleMarshal() {
 	type ColorGroup struct {
 		ID     int
@@ -27,9 +29,10 @@ func ExampleMarshal() {
 		fmt.Println("error:", err)
 	}
 	os.Stdout.Write(b)
+	// Output:
+	// {"ID":1,"Name":"Reds","Colors":["Crimson","Red","Ruby","Maroon"]}
 }
 
-// [{Name:Platypus Order:Monotremata} {Name:Quoll Order:Dasyuromorphia}]
 func ExampleUnmarshal() {
 	var jsonBlob = []byte(`[
 		{"Name": "Platypus", "Order": "Monotremata"},
@@ -45,4 +48,36 @@ func ExampleUnmarshal() {
 		fmt.Println("error:", err)
 	}
 	fmt.Printf("%+v", animals)
+	// Output:
+	// [{Name:Platypus Order:Monotremata} {Name:Quoll Order:Dasyuromorphia}]
+}
+
+// This example uses a Decoder to decode a stream of distinct JSON values.
+func ExampleDecoder() {
+	const jsonStream = `
+		{"Name": "Ed", "Text": "Knock knock."}
+		{"Name": "Sam", "Text": "Who's there?"}
+		{"Name": "Ed", "Text": "Go fmt."}
+		{"Name": "Sam", "Text": "Go fmt who?"}
+		{"Name": "Ed", "Text": "Go fmt yourself!"}
+	`
+	type Message struct {
+		Name, Text string
+	}
+	dec := json.NewDecoder(strings.NewReader(jsonStream))
+	for {
+		var m Message
+		if err := dec.Decode(&m); err == io.EOF {
+			break
+		} else if err != nil {
+			log.Fatal(err)
+		}
+		fmt.Printf("%s: %s\n", m.Name, m.Text)
+	}
+	// Output:
+	// Ed: Knock knock.
+	// Sam: Who's there?
+	// Ed: Go fmt.
+	// Sam: Go fmt who?
+	// Ed: Go fmt yourself!
 }
diff --git a/src/pkg/encoding/json/scanner.go b/src/pkg/encoding/json/scanner.go
index 2661f410e..054b6b3d5 100644
--- a/src/pkg/encoding/json/scanner.go
+++ b/src/pkg/encoding/json/scanner.go
@@ -185,18 +185,9 @@ func isSpace(c rune) bool {
 	return c == ' ' || c == '\t' || c == '\r' || c == '\n'
 }
 
-// NOTE(rsc): The various instances of
-//
-//	if c <= ' ' && (c == ' ' || c == '\t' || c == '\r' || c == '\n')
-//
-// below should all be if c <= ' ' && isSpace(c), but inlining
-// the checks makes a significant difference (>10%) in tight loops
-// such as nextValue.  These should be rewritten with the clearer
-// function call once 6g knows to inline the call.
-
 // stateBeginValueOrEmpty is the state after reading `[`.
 func stateBeginValueOrEmpty(s *scanner, c int) int {
-	if c <= ' ' && (c == ' ' || c == '\t' || c == '\r' || c == '\n') {
+	if c <= ' ' && isSpace(rune(c)) {
 		return scanSkipSpace
 	}
 	if c == ']' {
@@ -207,7 +198,7 @@ func stateBeginValueOrEmpty(s *scanner, c int) int {
 
 // stateBeginValue is the state at the beginning of the input.
 func stateBeginValue(s *scanner, c int) int {
-	if c <= ' ' && (c == ' ' || c == '\t' || c == '\r' || c == '\n') {
+	if c <= ' ' && isSpace(rune(c)) {
 		return scanSkipSpace
 	}
 	switch c {
@@ -247,7 +238,7 @@ func stateBeginValue(s *scanner, c int) int {
 
 // stateBeginStringOrEmpty is the state after reading `{`.
 func stateBeginStringOrEmpty(s *scanner, c int) int {
-	if c <= ' ' && (c == ' ' || c == '\t' || c == '\r' || c == '\n') {
+	if c <= ' ' && isSpace(rune(c)) {
 		return scanSkipSpace
 	}
 	if c == '}' {
@@ -260,7 +251,7 @@ func stateBeginStringOrEmpty(s *scanner, c int) int {
 
 // stateBeginString is the state after reading `{"key": value,`.
 func stateBeginString(s *scanner, c int) int {
-	if c <= ' ' && (c == ' ' || c == '\t' || c == '\r' || c == '\n') {
+	if c <= ' ' && isSpace(rune(c)) {
 		return scanSkipSpace
 	}
 	if c == '"' {
@@ -280,7 +271,7 @@ func stateEndValue(s *scanner, c int) int {
 		s.endTop = true
 		return stateEndTop(s, c)
 	}
-	if c <= ' ' && (c == ' ' || c == '\t' || c == '\r' || c == '\n') {
+	if c <= ' ' && isSpace(rune(c)) {
 		s.step = stateEndValue
 		return scanSkipSpace
 	}
diff --git a/src/pkg/encoding/json/stream.go b/src/pkg/encoding/json/stream.go
index f24763950..7d1cc5f11 100644
--- a/src/pkg/encoding/json/stream.go
+++ b/src/pkg/encoding/json/stream.go
@@ -19,6 +19,9 @@ type Decoder struct {
 }
 
 // NewDecoder returns a new decoder that reads from r.
+//
+// The decoder introduces its own buffering and may
+// read data from r beyond the JSON values requested.
 func NewDecoder(r io.Reader) *Decoder {
 	return &Decoder{r: r}
 }