zapcore: Ignore nil Entry.Time in encoders (#1369)

Per the comment on `Encoder.EncodeEntry`, any fields that are empty
including fields on the `Entry` type should be omitted. Omit the `Time`
field when we have empty time.
This also aligns with slog.Handler contract.

Refs #1334
Discovered by #1335

---------

Co-authored-by: Abhinav Gupta <mail@abhinavg.net>

zapcore/console_encoder.go

@@ -77,7 +77,7 @@ func (c consoleEncoder) EncodeEntry(ent Entry, fields []Field) (*buffer.Buffer,
 	// If this ever becomes a performance bottleneck, we can implement
 	// ArrayEncoder for our plain-text format.
 	arr := getSliceEncoder()
-	if c.TimeKey != "" && c.EncodeTime != nil {
+	if c.TimeKey != "" && c.EncodeTime != nil && !ent.Time.IsZero() {
 		c.EncodeTime(ent.Time, arr)
 	}
 	if c.LevelKey != "" && c.EncodeLevel != nil {

zapcore/console_encoder_test.go

@@ -21,6 +21,7 @@ package zapcore_test
 
 import (
 	"testing"
+	"time"
 
 	"github.com/stretchr/testify/assert"
 	. "go.uber.org/zap/zapcore"
@@ -35,6 +36,50 @@ var testEntry = Entry{
 	Caller:     EntryCaller{Defined: true, File: "foo.go", Line: 42, Function: "foo.Foo"},
 }
 
+func TestConsoleEncodeEntry(t *testing.T) {
+	tests := []struct {
+		desc     string
+		expected string
+		ent      Entry
+		fields   []Field
+	}{
+		{
+			desc:     "info no fields",
+			expected: "2018-06-19T16:33:42Z\tinfo\tbob\tlob law\n",
+			ent: Entry{
+				Level:      InfoLevel,
+				Time:       time.Date(2018, 6, 19, 16, 33, 42, 99, time.UTC),
+				LoggerName: "bob",
+				Message:    "lob law",
+			},
+		},
+		{
+			desc:     "zero_time_omitted",
+			expected: "info\tname\tmessage\n",
+			ent: Entry{
+				Level:      InfoLevel,
+				Time:       time.Time{},
+				LoggerName: "name",
+				Message:    "message",
+			},
+		},
+	}
+
+	cfg := testEncoderConfig()
+	cfg.EncodeTime = RFC3339TimeEncoder
+	enc := NewConsoleEncoder(cfg)
+
+	for _, tt := range tests {
+		t.Run(tt.desc, func(t *testing.T) {
+			buf, err := enc.EncodeEntry(tt.ent, tt.fields)
+			if assert.NoError(t, err, "Unexpected console encoding error.") {
+				assert.Equal(t, tt.expected, buf.String(), "Incorrect encoded entry.")
+			}
+			buf.Free()
+		})
+	}
+}
+
 func TestConsoleSeparator(t *testing.T) {
 	tests := []struct {
 		desc        string

zapcore/json_encoder.go

@@ -372,7 +372,7 @@ func (enc *jsonEncoder) EncodeEntry(ent Entry, fields []Field) (*buffer.Buffer,
 			final.AppendString(ent.Level.String())
 		}
 	}
-	if final.TimeKey != "" {
+	if final.TimeKey != "" && !ent.Time.IsZero() {
 		final.AddTime(final.TimeKey, ent.Time)
 	}
 	if ent.LoggerName != "" && final.NameKey != "" {

zapcore/json_encoder_test.go

@@ -109,6 +109,20 @@ func TestJSONEncodeEntry(t *testing.T) {
 				}),
 			},
 		},
+		{
+			desc: "zero_time_omitted",
+			expected: `{
+				"L": "info",
+				"N": "name",
+				"M": "message"
+			}`,
+			ent: zapcore.Entry{
+				Level:      zapcore.InfoLevel,
+				Time:       time.Time{},
+				LoggerName: "name",
+				Message:    "message",
+			},
+		},
 	}
 
 	enc := zapcore.NewJSONEncoder(zapcore.EncoderConfig{