Introducing Metadata.UnmarshalJSON

Let the metadata package own the json unmarshaling. This way we do not need to maintain a public wrapper and it simply's the code using metadata a little as well.

Author: boekkooi-fresh

metadata/metadata.go

@@ -3,6 +3,7 @@ package metadata
 import (
 	"encoding/json"
 
+	"github.com/mailru/easyjson"
 	"github.com/mailru/easyjson/jlexer"
 )
 
@@ -98,25 +99,24 @@ func (v *valueData) MarshalJSON() ([]byte, error) {
 	return json.Marshal(v.AsMap())
 }
 
-// JSONMetadata is a special struct to UnmarshalJSON metadata
-type JSONMetadata struct {
-	Metadata Metadata
-}
+func UnmarshalJSON(json []byte) (Metadata, error) {
+	wrapper := jsonMetadata{
+		Metadata: New(),
+	}
 
-var (
-	// Ensure JSONMetadata implements the json.Unmarshaler interface
-	_ json.Unmarshaler = &JSONMetadata{}
-)
+	if err := easyjson.Unmarshal(json, &wrapper); err != nil {
+		return nil, err
+	}
+	return wrapper.Metadata, nil
+}
 
-// UnmarshalJSON unmarshal the json into Metdadata
-func (j *JSONMetadata) UnmarshalJSON(data []byte) error {
-	r := jlexer.Lexer{Data: data}
-	j.UnmarshalEasyJSON(&r)
-	return r.Error()
+// jsonMetadata is a special struct to UnmarshalJSON metadata
+type jsonMetadata struct {
+	Metadata Metadata
 }
 
 // UnmarshalEasyJSON supports easyjson.Unmarshaler interface
-func (j *JSONMetadata) UnmarshalEasyJSON(in *jlexer.Lexer) {
+func (j *jsonMetadata) UnmarshalEasyJSON(in *jlexer.Lexer) {
 	metadata := New()
 
 	isTopLevel := in.IsStart()

metadata/metadata_test.go

@@ -8,7 +8,6 @@ import (
 	"time"
 
 	"github.com/hellofresh/goengine/metadata"
-	"github.com/mailru/easyjson"
 	"github.com/stretchr/testify/assert"
 )
 
@@ -215,12 +214,11 @@ func TestMetadata_MarshalJSON(t *testing.T) {
 func TestJSONMetadata_UnmarshalJSON(t *testing.T) {
 	for _, testCase := range jsonTestCases {
 		t.Run(testCase.title, func(t *testing.T) {
-			var m metadata.JSONMetadata
-			err := json.Unmarshal([]byte(testCase.json), &m)
+			m, err := metadata.UnmarshalJSON([]byte(testCase.json))
 
 			// Need to use AsMap otherwise we can have inconsistent tests results.
 			if assert.NoError(t, err) {
-				assert.Equal(t, testCase.metadata().AsMap(), m.Metadata.AsMap())
+				assert.Equal(t, testCase.metadata().AsMap(), m.AsMap())
 			}
 		})
 	}
@@ -231,21 +229,7 @@ func BenchmarkJSONMetadata_UnmarshalJSON(b *testing.B) {
 
 	b.ResetTimer()
 	for i := 0; i < b.N; i++ {
-		var m metadata.JSONMetadata
-		err := json.Unmarshal(payload, &m)
-		if err != nil {
-			b.Fail()
-		}
-	}
-}
-
-func BenchmarkJSONMetadata_UnmarshalEasyJSON(b *testing.B) {
-	payload := []byte(`{"_aggregate_id": "b9ebca7a-c1eb-40dd-94a4-fac7c5e84fb5", "_aggregate_type": "bank_account", "_aggregate_version": 1}`)
-
-	b.ResetTimer()
-	for i := 0; i < b.N; i++ {
-		var m metadata.JSONMetadata
-		err := easyjson.Unmarshal(payload, &m)
+		_, err := metadata.UnmarshalJSON(payload)
 		if err != nil {
 			b.Fail()
 		}

strategy/json/sql/message_factory_aggregate.go

@@ -9,7 +9,6 @@ import (
 	"github.com/hellofresh/goengine/aggregate"
 	driverSQL "github.com/hellofresh/goengine/driver/sql"
 	"github.com/hellofresh/goengine/metadata"
-	"github.com/mailru/easyjson"
 )
 
 // Ensure that AggregateChangedFactory satisfies the MessageFactory interface
@@ -78,11 +77,10 @@ func (a *aggregateChangedEventStream) Message() (goengine.Message, int64, error)
 		return nil, 0, err
 	}
 
-	metadataWrapper := metadata.JSONMetadata{Metadata: metadata.New()}
-	if err := easyjson.Unmarshal(jsonMetadata, &metadataWrapper); err != nil {
+	meta, err := metadata.UnmarshalJSON(jsonMetadata)
+	if err != nil {
 		return nil, 0, err
 	}
-	meta := metadataWrapper.Metadata
 
 	payload, err := a.payloadFactory.CreatePayload(eventName, jsonPayload)
 	if err != nil {