devslog

README

🧻 devslog - Go slog.Handler for development

devslog is a zero dependency structured logging handler for Go's log/slog package with pretty and colorful output for developers.

Devslog output

Compared to

TextHandler

JSONHandler

Install

go get github.com/golang-cz/devslog@latest

Examples

Logger without options

logger := slog.New(devslog.NewHandler(os.Stdout, nil))

// optional: set global logger
slog.SetDefault(logger)

Logger with custom options

// new logger with options
opts := &devslog.Options{
	MaxSlicePrintSize: 4,
	SortKeys:          true,
	TimeFormat:        "[04:05]",
	NewLineAfterLog:   true,
	DebugColor:        devslog.Magenta,
	StringerFormatter: true,
}

logger := slog.New(devslog.NewHandler(os.Stdout, opts))

// optional: set global logger
slog.SetDefault(logger)

Logger with default slog options

Handler accepts default slog.HandlerOptions

// slog.HandlerOptions
slogOpts := &slog.HandlerOptions{
	AddSource:   true,
	Level:       slog.LevelDebug,
}

// new logger with options
opts := &devslog.Options{
	HandlerOptions:    slogOpts,
	MaxSlicePrintSize: 4,
	SortKeys:          true,
	NewLineAfterLog:   true,
	StringerFormatter: true,
}

logger := slog.New(devslog.NewHandler(os.Stdout, opts))

// optional: set global logger
slog.SetDefault(logger)

Example usage

slogOpts := &slog.HandlerOptions{
	AddSource: true,
	Level:     slog.LevelDebug,
}

var logger *slog.Logger
if production {
	logger = slog.New(slog.NewJSONHandler(os.Stdout, slogOpts))
} else {
	opts := &devslog.Options{
		HandlerOptions:    slogOpts,
		MaxSlicePrintSize: 10,
		SortKeys:          true,
		NewLineAfterLog:   true,
		StringerFormatter: true,
	}

	logger = slog.New(devslog.NewHandler(os.Stdout, opts))
}

// optional: set global logger
slog.SetDefault(logger)

Options

Parameter	Description	Default	Value
MaxSlicePrintSize	Specifies the maximum number of elements to print for a slice.	50	uint
SortKeys	Determines if attributes should be sorted by keys.	false	bool
TimeFormat	Time format for timestamp.	"[15:04:05]"	string
NewLineAfterLog	Add blank line after each log	false	bool
StringIndentation	Indent \n in strings	false	bool
DebugColor	Color for Debug level	devslog.Blue	devslog.Color (uint)
InfoColor	Color for Info level	devslog.Green	devslog.Color (uint)
WarnColor	Color for Warn level	devslog.Yellow	devslog.Color (uint)
ErrorColor	Color for Error level	devslog.Red	devslog.Color (uint)
MaxErrorStackTrace	Max stack trace frames for errors	0	uint
StringerFormatter	Use Stringer interface for formatting	false	bool
NoColor	Disable coloring	false	bool
SameSourceInfoColor	Keep same color for whole source info	false	bool

Documentation

Index

• func NewHandler(out io.Writer, o *Options) *developHandler
• type Color
• type Options

Functions

func NewHandler

func NewHandler(out io.Writer, o *Options) *developHandler

Types

type Color

type Color uint

const (
	UnknownColor Color = iota
	Black
	Red
	Green
	Yellow
	Blue
	Magenta
	Cyan
	White
)

type Options

type Options struct {
	// You can use standard slog.HandlerOptions, that would be used in production
	*slog.HandlerOptions

	// Max number of printed elements in slice.
	MaxSlicePrintSize uint

	// If the attributes should be sorted by keys
	SortKeys bool

	// Time format for timestamp, default format is "[15:04:05]"
	TimeFormat string

	// Add blank line after each log
	NewLineAfterLog bool

	// Indent \n in strings
	StringIndentation bool

	// Set color for Debug level, default: devslog.Blue
	DebugColor Color

	// Set color for Info level, default: devslog.Green
	InfoColor Color

	// Set color for Warn level, default: devslog.Yellow
	WarnColor Color

	// Set color for Error level, default: devslog.Red
	ErrorColor Color

	// Max stack trace frames when unwrapping errors
	MaxErrorStackTrace uint

	// Use method String() for formatting value
	StringerFormatter bool

	// Disable coloring
	NoColor bool

	// Keep same color for whole source info, helpful when you want to open the line of code from terminal, but the ANSI coloring codes are in link itself
	SameSourceInfoColor bool
}