codec: use stdlib time.Time encoding

The new json encoder has different behavior for encoding zero time.Time
values. This change forces the Marshal method to be called, which gets
back the previous behavior (always produce a string) at the cost of
doing an allocation.

Closes #1231

Signed-off-by: Hank Donnay <hdonnay@redhat.com>

internal/codec/codec.go

@@ -15,6 +15,10 @@ func init() {
 	// This is documented to cause "smart buffering".
 	jsonHandle.WriterBufferSize = 4096
 	jsonHandle.ReaderBufferSize = 4096
+	// Force calling time.Time's Marshal function. This causes an allocation on
+	// every time.Time value, but is the same behavior as the stdlib json
+	// encoder. If we decide nulls are OK, this should get removed.
+	jsonHandle.TimeNotBuiltin = true
 }
 
 // Encoder and decoder pools, to reuse if possible.

internal/codec/codec_test.go

@@ -1,11 +1,13 @@
 package codec
 
 import (
+	"bytes"
 	"encoding/json"
 	"fmt"
 	"os"
 	"strings"
 	"testing"
+	"time"
 
 	"github.com/google/go-cmp/cmp"
 )
@@ -72,3 +74,28 @@ func BenchmarkDecodeStdlib(b *testing.B) {
 		}
 	}
 }
+
+func TestTimeNotNull(t *testing.T) {
+	type s struct {
+		Time time.Time
+	}
+	var b bytes.Buffer
+	enc := GetEncoder(&b)
+	defer PutEncoder(enc)
+
+	// Example encoding of a populated time:
+	if err := enc.Encode(s{Time: time.Unix(0, 0).UTC()}); err != nil {
+		t.Error(err)
+	}
+	t.Log(b.String())
+	b.Reset()
+
+	// Now encode a zero time and make sure it's a string.
+	if err := enc.Encode(s{}); err != nil {
+		t.Error(err)
+	}
+	t.Log(b.String())
+	if strings.Contains(b.String(), "null") {
+		t.Error("wanted non-null encoding")
+	}
+}