types: ensure Entity marshals to JSON with a consistent ordering

Signed-off-by: Patrick Jakubowski <[email protected]>

internal/testutil/testutil.go

@@ -1,6 +1,8 @@
 package testutil
 
 import (
+	"bytes"
+	"encoding/json"
 	"errors"
 	"reflect"
 )
@@ -60,3 +62,15 @@ func Panic(t TB, f func()) {
 	}()
 	f()
 }
+
+// JSONMarshalsTo asserts that obj marshals as JSON to the given string, allowing for formatting differences and
+// displaying an easy-to-read diff.
+func JSONMarshalsTo[T any](t TB, obj T, want string) {
+	b, err := json.MarshalIndent(obj, "", "\t")
+	OK(t, err)
+
+	var wantBuf bytes.Buffer
+	err = json.Indent(&wantBuf, []byte(want), "", "\t")
+	OK(t, err)
+	Equals(t, string(b), wantBuf.String())
+}

types/entities_test.go

@@ -1,7 +1,6 @@
 package types_test
 
 import (
-	"bytes"
 	"encoding/json"
 	"testing"
 
@@ -25,16 +24,6 @@ func TestEntities(t *testing.T) {
 
 }
 
-func assertJSONEquals(t *testing.T, e any, want string) {
-	b, err := json.MarshalIndent(e, "", "\t")
-	testutil.OK(t, err)
-
-	var wantBuf bytes.Buffer
-	err = json.Indent(&wantBuf, []byte(want), "", "\t")
-	testutil.OK(t, err)
-	testutil.Equals(t, string(b), wantBuf.String())
-}
-
 func TestEntitiesJSON(t *testing.T) {
 	t.Parallel()
 	t.Run("Marshal", func(t *testing.T) {
@@ -52,7 +41,7 @@ func TestEntitiesJSON(t *testing.T) {
 		}
 		e[ent.UID] = ent
 		e[ent2.UID] = ent2
-		assertJSONEquals(
+		testutil.JSONMarshalsTo(
 			t,
 			e,
 			`[

types/entity.go

@@ -1,6 +1,10 @@
 package types
 
-import "encoding/json"
+import (
+	"encoding/json"
+	"slices"
+	"strings"
+)
 
 // An Entity defines the parents and attributes for an EntityUID.
 type Entity struct {
@@ -17,6 +21,13 @@ func (e Entity) MarshalJSON() ([]byte, error) {
 		parents = append(parents, ImplicitlyMarshaledEntityUID(p))
 		return true
 	})
+	slices.SortFunc(parents, func(a, b ImplicitlyMarshaledEntityUID) int {
+		if cmp := strings.Compare(string(a.Type), string(b.Type)); cmp != 0 {
+			return cmp
+		}
+
+		return strings.Compare(string(a.ID), string(b.ID))
+	})
 
 	m := struct {
 		UID        ImplicitlyMarshaledEntityUID   `json:"uid"`

types/entity_test.go

@@ -27,3 +27,31 @@ func TestEntityIsZero(t *testing.T) {
 		})
 	}
 }
+
+func TestEntityMarshalJSON(t *testing.T) {
+	t.Parallel()
+	e := types.Entity{
+		UID: types.NewEntityUID("FooType", "1"),
+		Parents: types.NewEntityUIDSet(
+			types.NewEntityUID("BazType", "1"),
+			types.NewEntityUID("BarType", "2"),
+			types.NewEntityUID("BarType", "1"),
+			types.NewEntityUID("QuuxType", "30"),
+			types.NewEntityUID("QuuxType", "3"),
+		),
+		Attributes: types.Record{},
+	}
+
+	testutil.JSONMarshalsTo(t, e,
+		`{
+			"uid": {"type":"FooType","id":"1"},
+			"parents": [
+				{"type":"BarType","id":"1"},
+				{"type":"BarType","id":"2"},
+				{"type":"BazType","id":"1"},
+				{"type":"QuuxType","id":"3"},
+				{"type":"QuuxType","id":"30"}
+			],
+			"attrs":{}
+		}`)
+}