Sort map entries marshalling dag-json

codec/dagjson/marshal.go

@@ -3,6 +3,7 @@ package dagjson
 import (
 	"encoding/base64"
 	"fmt"
+	"sort"
 
 	"github.com/polydawn/refmt/shared"
 	"github.com/polydawn/refmt/tok"
@@ -31,21 +32,32 @@ func Marshal(n ipld.Node, sink shared.TokenSink, allowLinks bool) error {
 		if _, err := sink.Step(&tk); err != nil {
 			return err
 		}
-		// Emit map contents (and recurse).
+		// Collect map entries, then sort by key
+		type entry struct {
+			key   string
+			value ipld.Node
+		}
+		entries := []entry{}
 		for itr := n.MapIterator(); !itr.Done(); {
 			k, v, err := itr.Next()
 			if err != nil {
 				return err
 			}
-			tk.Type = tok.TString
-			tk.Str, err = k.AsString()
+			keyStr, err := k.AsString()
 			if err != nil {
 				return err
 			}
+			entries = append(entries, entry{keyStr, v})
+		}
+		sort.Slice(entries, func(i, j int) bool { return entries[i].key < entries[j].key })
+		// Emit map contents (and recurse).
+		for _, e := range entries {
+			tk.Type = tok.TString
+			tk.Str = e.key
 			if _, err := sink.Step(&tk); err != nil {
 				return err
 			}
-			if err := Marshal(v, sink, allowLinks); err != nil {
+			if err := Marshal(e.value, sink, allowLinks); err != nil {
 				return err
 			}
 		}

codec/dagjson/roundtripBytes_test.go

@@ -15,7 +15,7 @@ var byteNode = fluent.MustBuildMap(basicnode.Prototype__Map{}, 4, func(na fluent
 	na.AssembleEntry("plain").AssignString("olde string")
 	na.AssembleEntry("bytes").AssignBytes([]byte("deadbeef"))
 })
-var byteSerial = `{"plain":"olde string","bytes":{"/":{"bytes":"ZGVhZGJlZWY="}}}`
+var byteSerial = `{"bytes":{"/":{"bytes":"ZGVhZGJlZWY="}},"plain":"olde string"}`
 
 func TestRoundtripBytes(t *testing.T) {
 	t.Run("encoding", func(t *testing.T) {

codec/dagjson/roundtrip_test.go

@@ -27,7 +27,7 @@ var n = fluent.MustBuildMap(basicnode.Prototype__Map{}, 4, func(na fluent.MapAss
 		})
 	})
 })
-var serial = `{"plain":"olde string","map":{"one":1,"two":2},"list":["three","four"],"nested":{"deeper":["things"]}}`
+var serial = `{"list":["three","four"],"map":{"one":1,"two":2},"nested":{"deeper":["things"]},"plain":"olde string"}`
 
 func TestRoundtrip(t *testing.T) {
 	t.Run("encoding", func(t *testing.T) {