*: all builtin loggers correctly handle empty config object

Makefile

@@ -14,4 +14,5 @@ coverage:
 
 clean:
 	go clean
+	rm -f clog.log
 	rm -f coverage.out

console.go

@@ -47,6 +47,10 @@ func (l *consoleLogger) Write(m Messager) error {
 
 func init() {
 	NewRegister(ModeConsole, func(v interface{}) (Logger, error) {
+		if v == nil {
+			v = ConsoleConfig{}
+		}
+
 		cfg, ok := v.(ConsoleConfig)
 		if !ok {
 			return nil, fmt.Errorf("invalid config object: want %T got %T", ConsoleConfig{}, v)

console_test.go

@@ -16,6 +16,10 @@ func Test_ModeConsole(t *testing.T) {
 		wantLevel Level
 		wantErr   error
 	}{
+		{
+			name:    "nil config",
+			wantErr: nil,
+		},
 		{
 			name: "valid config",
 			config: ConsoleConfig{

discord.go

@@ -165,6 +165,10 @@ func (l *discordLogger) Write(m Messager) error {
 
 func init() {
 	NewRegister(ModeDiscord, func(v interface{}) (Logger, error) {
+		if v == nil {
+			v = DiscordConfig{}
+		}
+
 		cfg, ok := v.(DiscordConfig)
 		if !ok {
 			return nil, fmt.Errorf("invalid config object: want %T got %T", DiscordConfig{}, v)

discord_test.go

@@ -20,6 +20,10 @@ func Test_ModeDiscord(t *testing.T) {
 		wantLevel Level
 		wantErr   error
 	}{
+		{
+			name:    "nil config",
+			wantErr: errors.New("initialize logger: empty URL"),
+		},
 		{
 			name: "valid config",
 			config: DiscordConfig{

file.go

@@ -236,6 +236,12 @@ func (l *fileLogger) init() error {
 
 func init() {
 	NewRegister(ModeFile, func(v interface{}) (Logger, error) {
+		if v == nil {
+			v = FileConfig{
+				Filename: "clog.log",
+			}
+		}
+
 		cfg, ok := v.(FileConfig)
 		if !ok {
 			return nil, fmt.Errorf("invalid config object: want %T got %T", FileConfig{}, v)

file_test.go

@@ -19,6 +19,10 @@ func Test_ModeFile(t *testing.T) {
 		wantLevel Level
 		wantErr   error
 	}{
+		{
+			name:    "nil config",
+			wantErr: nil,
+		},
 		{
 			name: "valid config",
 			config: FileConfig{

slack.go

@@ -107,6 +107,10 @@ func (l *slackLogger) Write(m Messager) error {
 
 func init() {
 	NewRegister(ModeSlack, func(v interface{}) (Logger, error) {
+		if v == nil {
+			v = SlackConfig{}
+		}
+
 		cfg, ok := v.(SlackConfig)
 		if !ok {
 			return nil, fmt.Errorf("invalid config object: want %T got %T", SlackConfig{}, v)

slack_test.go

@@ -19,6 +19,10 @@ func Test_ModeSlack(t *testing.T) {
 		wantLevel Level
 		wantErr   error
 	}{
+		{
+			name:    "nil config",
+			wantErr: errors.New("initialize logger: empty URL"),
+		},
 		{
 			name: "valid config",
 			config: SlackConfig{