fix(GODT-2212): Preserve header order when building messages

Ensure order of parsed header field is recorded alongside the values.

go.mod

@@ -18,6 +18,7 @@ require (
 	github.com/sirupsen/logrus v1.9.2
 	github.com/stretchr/testify v1.8.3
 	github.com/urfave/cli/v2 v2.24.4
+	gitlab.com/c0b/go-ordered-json v0.0.0-20201030195603-febf46534d5a
 	go.uber.org/goleak v1.2.1
 	golang.org/x/exp v0.0.0-20230522175609-2e198f4a06a1
 	golang.org/x/net v0.10.0

go.sum

@@ -120,6 +120,8 @@ github.com/urfave/cli/v2 v2.24.4/go.mod h1:GHupkWPMM0M/sj1a2b4wUrWBPzazNrIjouW6f
 github.com/xrash/smetrics v0.0.0-20201216005158-039620a65673 h1:bAn7/zixMGCfxrRTfdpNzjtPYqr8smhKouy9mxVdGPU=
 github.com/xrash/smetrics v0.0.0-20201216005158-039620a65673/go.mod h1:N3UwUGtsrSj3ccvlPHLoLsHnpR27oXr4ZE984MbSER8=
 github.com/yuin/goldmark v1.4.13/go.mod h1:6yULJ656Px+3vBD8DxQVa3kxgyrAnzto9xy5taEt/CY=
+gitlab.com/c0b/go-ordered-json v0.0.0-20201030195603-febf46534d5a h1:DxppxFKRqJ8WD6oJ3+ZXKDY0iMONQDl5UTg2aTyHh8k=
+gitlab.com/c0b/go-ordered-json v0.0.0-20201030195603-febf46534d5a/go.mod h1:NREvu3a57BaK0R1+ztrEzHWiZAihohNLQ6trPxlIqZI=
 go.uber.org/goleak v1.2.1 h1:NBol2c7O1ZokfZ0LEU9K6Whx/KnwvepVetCUhtKja4A=
 go.uber.org/goleak v1.2.1/go.mod h1:qlT2yGI9QafXHhZZLxlSuNsMw3FFLxBr+tBRlmO1xH4=
 golang.org/x/arch v0.0.0-20210923205945-b76863e36670/go.mod h1:5om86z9Hs0C8fWVUuoMHwpExlXzs5Tkyp9hOrfG7pp8=

header_types.go

@@ -3,33 +3,50 @@ package proton
 import (
 	"encoding/json"
 	"errors"
+	"gitlab.com/c0b/go-ordered-json"
 )
 
 var ErrBadHeader = errors.New("bad header")
 
-type Headers map[string][]string
+type Headers struct {
+	Values map[string][]string
+	Order  []string
+}
 
 func (h *Headers) UnmarshalJSON(b []byte) error {
 	type rawHeaders map[string]any
 
 	raw := make(rawHeaders)
 
-	if err := json.Unmarshal(b, &raw); err != nil {
+	// Need to use a different type to deserialize, because there still is no official way for json to decode an object
+	// with the fields in order https://github.com/golang/go/issues/27179.
+	orderedMap := ordered.NewOrderedMap()
+	if err := orderedMap.UnmarshalJSON(b); err != nil {
 		return err
 	}
 
-	header := make(Headers)
+	header := Headers{
+		Values: make(map[string][]string, len(raw)),
+		Order:  make([]string, 0, len(raw)),
+	}
 
-	for key, val := range raw {
-		switch val := val.(type) {
+	iter := orderedMap.EntriesIter()
+
+	for {
+		entry, ok := iter()
+		if !ok {
+			break
+		}
+
+		switch val := entry.Value.(type) {
 		case string:
-			header[key] = []string{val}
+			header.Values[entry.Key] = []string{val}
 
 		case []any:
 			for _, val := range val {
 				switch val := val.(type) {
 				case string:
-					header[key] = append(header[key], val)
+					header.Values[entry.Key] = append(header.Values[entry.Key], val)
 
 				default:
 					return ErrBadHeader
@@ -39,9 +56,54 @@ func (h *Headers) UnmarshalJSON(b []byte) error {
 		default:
 			return ErrBadHeader
 		}
+
+		header.Order = append(header.Order, entry.Key)
 	}
 
 	*h = header
 
 	return nil
 }
+
+func (h Headers) MarshalJSON() ([]byte, error) {
+	// Manually Serialize to preserve oder
+	if len(h.Values) == 0 {
+		return []byte{'{', '}'}, nil
+	}
+
+	out := make([]byte, 0, 64)
+
+	out = append(out, '{')
+
+	for _, k := range h.Order {
+		v := h.Values[k]
+
+		if len(v) == 0 {
+			continue
+		}
+
+		key, err := json.Marshal(k)
+		if err != nil {
+			return nil, err
+		}
+
+		var val []byte
+		if len(v) == 1 {
+			val, err = json.Marshal(v[0])
+		} else {
+			val, err = json.Marshal(v)
+		}
+		if err != nil {
+			return nil, err
+		}
+
+		out = append(out, key...)
+		out = append(out, ':')
+		out = append(out, val...)
+		out = append(out, ',')
+	}
+
+	out[len(out)-1] = '}'
+
+	return out, nil
+}

header_types_test.go

@@ -0,0 +1,24 @@
+package proton
+
+import (
+	"encoding/json"
+	"github.com/stretchr/testify/require"
+	"testing"
+)
+
+func TestHeaders_MarshalInOrder(t *testing.T) {
+	jsonBytes := []byte(`{"zz":"v1","foo":["a","b"],"bar":"30"}`)
+
+	var h Headers
+
+	err := json.Unmarshal(jsonBytes, &h)
+	require.NoError(t, err)
+
+	expectedKeyOrder := []string{"zz", "foo", "bar"}
+
+	require.Equal(t, expectedKeyOrder, h.Order)
+
+	serializedJson, err := json.Marshal(h)
+	require.NoError(t, err)
+	require.Equal(t, jsonBytes, serializedJson)
+}

message_build.go

@@ -295,8 +295,8 @@ func getTextPartHeader(body []byte, mimeType rfc822.MIMEType) message.Header {
 func getAttachmentPartHeader(att Attachment) message.Header {
 	var header message.Header
 
-	for key, val := range att.Headers {
-		for _, val := range val {
+	for _, key := range att.Headers.Order {
+		for _, val := range att.Headers.Values[key] {
 			header.Add(key, val)
 		}
 	}

server/backend/message.go

@@ -237,10 +237,13 @@ func (msg *message) getParsedHeaders() proton.Headers {
 		panic(err)
 	}
 
-	parsed := make(proton.Headers)
+	parsed := proton.Headers{
+		Values: make(map[string][]string),
+	}
 
 	header.Entries(func(key, value string) {
-		parsed[key] = append(parsed[key], value)
+		parsed.Order = append(parsed.Order, key)
+		parsed.Values[key] = append(parsed.Values[key], value)
 	})
 
 	return parsed