events: marshal CodeCommitEventTime from a value receiver

events/code_commit.go

@@ -22,13 +22,10 @@ type CodeCommitEventTime time.Time
 // https://golang.org/pkg/time/#Parse
 const codeCommitEventTimeReference = "\"2006-01-2T15:04:05.000-0700\""
 
-func (t *CodeCommitEventTime) MarshalJSON() ([]byte, error) {
-	if t == nil {
-		return nil, errors.New("CodeCommitEventTime cannot be nil")
-	}
-
-	gt := time.Time(*t)
-	return []byte(gt.Format(codeCommitEventTimeReference)), nil
+// MarshalJSON has a value receiver so that a CodeCommitRecord marshals the
+// same whether it is passed by value or by pointer.
+func (t CodeCommitEventTime) MarshalJSON() ([]byte, error) {
+	return []byte(time.Time(t).Format(codeCommitEventTimeReference)), nil
 }
 
 func (t *CodeCommitEventTime) UnmarshalJSON(data []byte) error {

events/code_commit_test.go

@@ -1,7 +1,9 @@
 package events
 
 import (
+	"encoding/json"
 	"testing"
+	"time"
 
 	"github.com/aws/aws-lambda-go/events/test"
 )
@@ -174,3 +176,23 @@ func TestCodeCommitEvent(t *testing.T) {
 		})
 	}
 }
+
+func TestCodeCommitEventTimeMarshalsByValue(t *testing.T) {
+	want := CodeCommitEventTime(time.Date(2020, 1, 15, 1, 2, 3, 0, time.UTC))
+	record := CodeCommitRecord{EventTime: want}
+
+	// a record passed by value has non-addressable fields, so the marshaler
+	// must not need a pointer receiver
+	b, err := json.Marshal(record)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	var got CodeCommitRecord
+	if err := json.Unmarshal(b, &got); err != nil {
+		t.Fatalf("%s: %v", b, err)
+	}
+	if !time.Time(got.EventTime).Equal(time.Time(want)) {
+		t.Errorf("event time = %v, want %v", time.Time(got.EventTime), time.Time(want))
+	}
+}