Add OrderedObject Type for canonical json

Signed-off-by: Jessica Frazelle <acidburn@docker.com>

canonical/json/decode.go

@@ -174,6 +174,7 @@ type decodeState struct {
 	nextscan         scanner // for calls to nextValue
 	savedError       error
 	useNumber        bool
+	useOrderedObject bool
 }
 
 // errPhase is used for errors that should not happen unless
@@ -492,9 +493,13 @@ func (d *decodeState) object(v reflect.Value) {
 	}
 	v = pv
 
+	// If we are decoding into a OrderedObject then use an OrderedObject
+	// just for this particular object even if UseOrderedObject was not called.
+	forceOrderedObject := v.Type() == orderedObjectType
+
 	// Decoding into nil interface?  Switch to non-reflect code.
-	if v.Kind() == reflect.Interface && v.NumMethod() == 0 {
+	if (v.Kind() == reflect.Interface && v.NumMethod() == 0) || forceOrderedObject {
-		v.Set(reflect.ValueOf(d.objectInterface()))
+		v.Set(reflect.ValueOf(d.objectInterface(forceOrderedObject)))
 		return
 	}
 
@@ -831,7 +836,7 @@ func (d *decodeState) valueInterface() interface{} {
 	case scanBeginArray:
 		return d.arrayInterface()
 	case scanBeginObject:
-		return d.objectInterface()
+		return d.objectInterface(false)
 	case scanBeginLiteral:
 		return d.literalInterface()
 	}
@@ -865,9 +870,10 @@ func (d *decodeState) arrayInterface() []interface{} {
 	return v
 }
 
-// objectInterface is like object but returns map[string]interface{}.
+// objectInterface is like object but returns map[string]interface{} or []OrderedObject.
-func (d *decodeState) objectInterface() map[string]interface{} {
+func (d *decodeState) objectInterface(forceOrderedObject bool) interface{} {
 	m := make(map[string]interface{})
+	v := make(OrderedObject, 0)
 	for {
 		// Read opening " of string key or closing }.
 		op := d.scanWhile(scanSkipSpace)
@@ -897,7 +903,11 @@ func (d *decodeState) objectInterface() map[string]interface{} {
 		}
 
 		// Read value.
+		if d.useOrderedObject || forceOrderedObject {
+			v = append(v, Member{Key: key, Value: d.valueInterface()})
+		} else {
 			m[key] = d.valueInterface()
+		}
 
 		// Next token must be , or }.
 		op = d.scanWhile(scanSkipSpace)
@@ -908,6 +918,10 @@ func (d *decodeState) objectInterface() map[string]interface{} {
 			d.error(errPhase)
 		}
 	}
+
+	if d.useOrderedObject || forceOrderedObject {
+		return v
+	}
 	return m
 }
 

canonical/json/decode_test.go

@@ -202,6 +202,7 @@ type unmarshalTest struct {
 	out              interface{}
 	err              error
 	useNumber        bool
+	useOrderedObject bool
 }
 
 type Ambig struct {
@@ -413,6 +414,39 @@ var unmarshalTests = []unmarshalTest{
 		ptr: &map[time.Time]string{},
 		err: &UnmarshalTypeError{"object", reflect.TypeOf(map[time.Time]string{})},
 	},
+
+	// OrderedObject tests - into interface{}
+	{in: `{"a":"1","b":2,"c":3}`, ptr: new(interface{}), useOrderedObject: true,
+		out: OrderedObject{{"a", "1"}, {"b", float64(2)}, {"c", float64(3)}}},
+	{in: `[{"a":"1","b":2}]`, ptr: new(interface{}), useOrderedObject: true,
+		out: []interface{}{OrderedObject{{"a", "1"}, {"b", float64(2)}}}},
+	{in: `{"a":null,"b": {"c":true} }`, ptr: new(interface{}), useOrderedObject: true,
+		out: OrderedObject{{"a", nil}, {"b", OrderedObject{{"c", true}}}}},
+	{in: `{"T":[]}`, ptr: new(interface{}), useOrderedObject: true,
+		out: OrderedObject{{Key: "T", Value: []interface{}{}}}},
+	{in: `{"T":null}`, ptr: new(interface{}), useOrderedObject: true,
+		out: OrderedObject{{Key: "T", Value: nil}}},
+	// OrderedObject tests - into map[string]interface{}
+	{in: `{"a":"1","b":2,"c":3}`, ptr: new(map[string]interface{}), useOrderedObject: true,
+		out: map[string]interface{}{"a": "1", "b": float64(2), "c": float64(3)}},
+	{in: `{"a":null,"b": {"c":true} }`, ptr: new(map[string]interface{}), useOrderedObject: true,
+		out: map[string]interface{}{"a": nil, "b": OrderedObject{{"c", true}}}},
+	{in: `{"T":[]}`, ptr: new(map[string]interface{}), useOrderedObject: true,
+		out: map[string]interface{}{"T": []interface{}{}}},
+	{in: `{"T":null}`, ptr: new(map[string]interface{}), useOrderedObject: true,
+		out: map[string]interface{}{"T": nil}},
+	// OrderedObject tests - into OrderedObject
+	{in: `{"a":"1","b":2,"c":3}`, ptr: new(OrderedObject), useOrderedObject: true,
+		out: OrderedObject{{"a", "1"}, {"b", float64(2)}, {"c", float64(3)}}},
+	{in: `{"a":"1","b":2,"c":3}`, ptr: new(OrderedObject),
+		out: OrderedObject{{"a", "1"}, {"b", float64(2)}, {"c", float64(3)}}},
+	{in: `{"a":null,"b": {"c":true} }`, ptr: new(OrderedObject), useOrderedObject: true,
+		out: OrderedObject{{"a", nil}, {"b", OrderedObject{{"c", true}}}}},
+	{in: `{"a":null,"b": {"c":true} }`, ptr: new(OrderedObject),
+		out: OrderedObject{{"a", nil}, {"b", map[string]interface{}{"c": true}}}},
+	// OrderedObject tests -into []OrderedObject
+	{in: `[{"a":"1","b":2},{"c":3}]`, ptr: &[]OrderedObject{},
+		out: []OrderedObject{{{"a", "1"}, {"b", float64(2)}}, {{"c", float64(3)}}}},
 }
 
 func TestMarshal(t *testing.T) {
@@ -528,6 +562,9 @@ func TestUnmarshal(t *testing.T) {
 		if tt.useNumber {
 			dec.UseNumber()
 		}
+		if tt.useOrderedObject {
+			dec.UseOrderedObject()
+		}
 		if err := dec.Decode(v.Interface()); !reflect.DeepEqual(err, tt.err) {
 			t.Errorf("#%d: %v, want %v", i, err, tt.err)
 			continue
@@ -555,6 +592,9 @@ func TestUnmarshal(t *testing.T) {
 			if tt.useNumber {
 				dec.UseNumber()
 			}
+			if tt.useOrderedObject {
+				dec.UseOrderedObject()
+			}
 			if err := dec.Decode(vv.Interface()); err != nil {
 				t.Errorf("#%d: error re-unmarshaling %#q: %v", i, enc, err)
 				continue
@@ -1371,3 +1411,22 @@ func TestInvalidUnmarshal(t *testing.T) {
 		}
 	}
 }
+
+type Obj struct {
+	A int
+	B OrderedObject
+	C string
+}
+
+func TestUnmarshalOrdered(t *testing.T) {
+	var v Obj
+	buf := []byte(`{"A": 3, "B": { "A": 5, "B": null}, "C": "C"}`)
+	exp := Obj{A: 3, B: OrderedObject{{"A", float64(5)}, {"B", nil}}, C: "C"}
+	err := Unmarshal(buf, &v)
+	if err != nil {
+		t.Errorf("Unmarshal unexpected error: %v", err)
+	}
+	if !reflect.DeepEqual(exp, v) {
+		t.Errorf("%v, want %v", v, exp)
+	}
+}

canonical/json/encode.go

@@ -116,6 +116,9 @@ import (
 // The map's key type must be string; the object keys are used directly
 // as map keys.
 //
+// OrderedObject values encode as JSON objects.
+// The JSON keys are encoded in the order in which they appear in the OrderedObject.
+//
 // Pointer values encode as the value pointed to.
 // A nil pointer encodes as the null JSON object.
 //
@@ -350,6 +353,7 @@ func typeEncoder(t reflect.Type) encoderFunc {
 var (
 	marshalerType     = reflect.TypeOf(new(Marshaler)).Elem()
 	textMarshalerType = reflect.TypeOf(new(encoding.TextMarshaler)).Elem()
+	orderedObjectType = reflect.TypeOf(new(OrderedObject)).Elem()
 )
 
 // newTypeEncoder constructs an encoderFunc for a type.
@@ -373,6 +377,10 @@ func newTypeEncoder(t reflect.Type, allowAddr bool) encoderFunc {
 		}
 	}
 
+	if t == orderedObjectType {
+		return orderedObjectEncoder
+	}
+
 	switch t.Kind() {
 	case reflect.Bool:
 		return boolEncoder
@@ -629,6 +637,24 @@ func newMapEncoder(t reflect.Type) encoderFunc {
 	return me.encode
 }
 
+func orderedObjectEncoder(e *encodeState, v reflect.Value, quoted bool) {
+	if v.IsNil() {
+		e.WriteString("null")
+		return
+	}
+	e.WriteByte('{')
+	var ov OrderedObject = v.Interface().(OrderedObject)
+	for i, o := range ov {
+		if i > 0 {
+			e.WriteByte(',')
+		}
+		e.string(o.Key)
+		e.WriteByte(':')
+		e.reflectValue(reflect.ValueOf(o.Value))
+	}
+	e.WriteByte('}')
+}
+
 func encodeByteSlice(e *encodeState, v reflect.Value, _ bool) {
 	if v.IsNil() {
 		e.WriteString("null")

canonical/json/encode_test.go

@@ -530,3 +530,36 @@ func TestEncodeString(t *testing.T) {
 		}
 	}
 }
+
+type ObjEnc struct {
+   A int
+   B OrderedObject
+   C interface{}
+}
+
+var orderedObjectTests = []struct {
+   in  interface{}
+   out string
+}{
+   {OrderedObject{}, `{}`},
+   {OrderedObject{Member{"A", []int{1, 2, 3}}, Member{"B", 23}, Member{"C", "C"}}, `{"A":[1,2,3],"B":23,"C":"C"}`},
+   {ObjEnc{A: 234, B: OrderedObject{Member{"K", "V"}, Member{"V", 4}}}, `{"A":234,"B":{"K":"V","V":4},"C":null}`},
+   {ObjEnc{A: 234, B: OrderedObject{}, C: OrderedObject{{"A", 0}}}, `{"A":234,"B":{},"C":{"A":0}}`},
+   {[]OrderedObject{{{"A", "Ay"}, {"B", "Bee"}}, {{"A", "Nay"}}}, `[{"A":"Ay","B":"Bee"},{"A":"Nay"}]`},
+   {map[string]OrderedObject{"A": {{"A", "Ay"}, {"B", "Bee"}}}, `{"A":{"A":"Ay","B":"Bee"}}`},
+   {map[string]interface{}{"A": OrderedObject{{"A", "Ay"}, {"B", "Bee"}}}, `{"A":{"A":"Ay","B":"Bee"}}`},
+}
+
+func TestEncodeOrderedObject(t *testing.T) {
+   for i, o := range orderedObjectTests {
+       d, err := Marshal(o.in)
+       if err != nil {
+           t.Errorf("Unexpected error %v", err)
+           continue
+       }
+       ds := string(d)
+       if o.out != ds {
+           t.Errorf("#%d expected '%v', was '%v'", i, o.out, ds)
+       }
+   }
+}

canonical/json/example_test.go

@@ -6,12 +6,13 @@ package json_test
 
 import (
 	"bytes"
-	"encoding/json"
 	"fmt"
 	"io"
 	"log"
 	"os"
 	"strings"
+
+	"github.com/jfrazelle/go/canonical/json"
 )
 
 func ExampleMarshal() {
@@ -159,3 +160,43 @@ func ExampleIndent() {
 	// =	}
 	// =]
 }
+
+func ExampleOrderedObject() {
+	var jsonBlob = []byte(`[
+       {"name": "Issac Newton", "born": 1643, "died": 1727 },
+       {"name": "André-Marie Ampère", "born": 1777, "died": 1836 }
+   ]`)
+	var people []json.OrderedObject
+
+	// Decode JSON while preserving the order of JSON key pairs.
+	err := json.Unmarshal(jsonBlob, &people)
+	if err != nil {
+		fmt.Println("unmarshalling error:", err)
+	}
+	fmt.Printf("Decoded:\n")
+	for _, v := range people {
+		for _, a := range v {
+			fmt.Printf(" %v=%v", a.Key, a.Value)
+		}
+		fmt.Printf("\n")
+	}
+
+	// Encode JSON keys in the order defined by the OrderedObject.
+	person := json.OrderedObject{
+		{Key: "name", Value: "Hans Christian Ørsted"},
+		{Key: "born", Value: 1777},
+		{Key: "died", Value: 1851},
+		{Key: "nationality", Value: "Danish"},
+	}
+	b, err := json.Marshal(person)
+	if err != nil {
+		fmt.Println("marshalling error:", err)
+	}
+	fmt.Printf("Encoded:\n %v", string(b))
+	// Output:
+	// Decoded:
+	//  name=Issac Newton born=1643 died=1727
+	//  name=André-Marie Ampère born=1777 died=1836
+	// Encoded:
+	//  {"name":"Hans Christian Ørsted","born":1777,"died":1851,"nationality":"Danish"}
+}

canonical/json/stream.go

@@ -31,6 +31,10 @@ func NewDecoder(r io.Reader) *Decoder {
 // Number instead of as a float64.
 func (dec *Decoder) UseNumber() { dec.d.useNumber = true }
 
+// UseOrderedObject causes the Decoder to unmarshal an object into an interface{}
+// as a OrderedObject instead of as a map[string]interface{}.
+func (dec *Decoder) UseOrderedObject() { dec.d.useOrderedObject = true }
+
 // Decode reads the next JSON-encoded value from its
 // input and stores it in the value pointed to by v.
 //
@@ -198,3 +202,52 @@ func (m *RawMessage) UnmarshalJSON(data []byte) error {
 
 var _ Marshaler = (*RawMessage)(nil)
 var _ Unmarshaler = (*RawMessage)(nil)
+
+// Member is used to store key/value pairs in an OrderedObject.
+type Member struct {
+	Key   string
+	Value interface{}
+}
+
+// OrderedObject stores the key/value pairs of a JSON object in the order
+// in which they appeared in the original document. See the documentation for UseOrderedObject on the Decoder.
+//
+// OrderedObject is used to enable decoding of arbitrary JSON objects while preserving
+// the order of the keys. Unmarshal and Decoder.Decode are supported.
+//
+//   var o OrderedObject
+//   Unmarshal(json, &o)     // decode JSON object, while preserving key order
+//
+//   var oa []OrderedObject
+//   Unmarshal(json, &oa)    // decode an array of JSON objects, while preserving key order
+//
+//   var v interface{}
+//   d := new Decoder(json)
+//   d.UseOrderedObject()    // decode all JSON objects as OrderedObject rather than map[string]interface{}
+//   d.Decode(&v)
+//
+//   type A struct {
+//       B     bool
+//       Inner OrderedObject
+//       I     int
+//   }
+//   var a A
+//   Unmarshal(&a)           // decode A as a JSON object with Inner as a nested object, preserving key order
+//
+// OrderedObject can also be used to encode a JSON object in
+// a specified order. Marshal and Encoder.Encode are supported.
+//
+//    var o OrderedObject
+//    Marshal(o)             // encode JSON object, each with keys in OrderedObject order
+//
+//    var oa []OrderedObject
+//    Marshal(oa)            // encode an array of JSON objects, with keys in OrderedObject order
+//
+//    type A struct {
+//       B     bool
+//       Inner OrderedObject
+//       I     int
+//    }
+//    var a A = createA()
+//    Marshal(a)             // encode A as a JSON object with Inner as a nested object
+type OrderedObject []Member