Make AppendKey in json inlinable

internal/json/base.go

@@ -4,9 +4,8 @@ type Encoder struct{}
 
 // AppendKey appends a new key to the output JSON.
 func (e Encoder) AppendKey(dst []byte, key string) []byte {
-	if len(dst) > 1 && dst[len(dst)-1] != '{' {
+	if dst[len(dst)-1] != '{' {
 		dst = append(dst, ',')
 	}
-	dst = e.AppendString(dst, key)
-	return append(dst, ':')
-}
+	return append(e.AppendString(dst, key), ':')
+}

internal/json/types.go

@@ -379,11 +379,10 @@ func (Encoder) AppendObjectData(dst []byte, o []byte) []byte {
 	//    to separate with existing content OR
 	// 3. existing content has already other fields
 	if o[0] == '{' {
-		if len(dst) == 0 {
-			o = o[1:]
-		} else {
-			o[0] = ','
+		if len(dst) > 1 {
+			dst = append(dst, ',')
 		}
+		o = o[1:]
 	} else if len(dst) > 1 {
 		dst = append(dst, ',')
 	}

log.go

@@ -234,6 +234,10 @@ func (l Logger) With() Context {
 	l.context = make([]byte, 0, 500)
 	if context != nil {
 		l.context = append(l.context, context...)
+	} else {
+		// This is needed for AppendKey to not check len of input
+		// thus making it inlinable
+		l.context = enc.AppendBeginMarker(l.context)
 	}
 	return Context{l}
 }
@@ -415,7 +419,7 @@ func (l *Logger) newEvent(level Level, done func(string)) *Event {
 	if level != NoLevel {
 		e.Str(LevelFieldName, LevelFieldMarshalFunc(level))
 	}
-	if l.context != nil && len(l.context) > 0 {
+	if l.context != nil && len(l.context) > 1 {
 		e.buf = enc.AppendObjectData(e.buf, l.context)
 	}
 	return e