Add ExcludeKey option to TextFormatter

text_formatter.go

@@ -28,6 +28,10 @@ func init() {
 
 // TextFormatter formats logs into text
 type TextFormatter struct {
+	// Set to true if want the log not to contain the startingKey, e.g.
+	// 0001-01-01T00:00:00Z warning message
+	ExcludeKey bool
+
 	// Set to true to bypass checking for a TTY before outputting colors.
 	ForceColors bool
 
@@ -320,8 +324,10 @@ func (f *TextFormatter) appendKeyValue(b *bytes.Buffer, key string, value interf
 	if b.Len() > 0 {
 		b.WriteByte(' ')
 	}
-	b.WriteString(key)
-	b.WriteByte('=')
+	if !f.ExcludeKey {
+		b.WriteString(key)
+		b.WriteByte('=')
+	}
 	f.appendValue(b, value)
 }
 
@@ -331,9 +337,14 @@ func (f *TextFormatter) appendValue(b *bytes.Buffer, value interface{}) {
 		stringVal = fmt.Sprint(value)
 	}
 
-	if !f.needsQuoting(stringVal) {
+	// write value without quoting directly when ExcludeKey is true
+	if f.ExcludeKey {
 		b.WriteString(stringVal)
 	} else {
-		b.WriteString(fmt.Sprintf("%q", stringVal))
+		if !f.needsQuoting(stringVal) {
+			b.WriteString(stringVal)
+		} else {
+			b.WriteString(fmt.Sprintf("%q", stringVal))
+		}
 	}
 }

text_formatter_test.go

@@ -598,3 +598,22 @@ func TestCustomSorting(t *testing.T) {
 	require.NoError(t, err)
 	require.True(t, strings.HasPrefix(string(b), "prefix="), "format output is %q", string(b))
 }
+
+func TestFormattingNotContainStartingKey(t *testing.T) {
+	tf := &TextFormatter{ExcludeKey: true}
+
+	testCases := []struct {
+		value    string
+		expected string
+	}{
+		{`foo`, "0001-01-01T00:00:00Z panic foo\n"},
+	}
+
+	for _, tc := range testCases {
+		b, _ := tf.Format(WithField("test", tc.value))
+
+		if string(b) != tc.expected {
+			t.Errorf("formatting expected for %q (result was %q instead of %q)", tc.value, string(b), tc.expected)
+		}
+	}
+}