82 lines
2.5 KiB
Go
82 lines
2.5 KiB
Go
// Package logger wraps log/slog with a thin, ergonomic API.
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//
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// The key addition over raw slog is the WithField / WithFields helpers that
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// return a *Logger (not a *slog.Logger), so callers stay in the typed world
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// and can chain field attachments without importing slog directly.
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//
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// Usage:
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//
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// log, _ := logger.New("info")
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// log.Info("server started")
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//
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// req := log.WithField("request_id", rid).WithField("user_id", uid)
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// req.Info("handling request")
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package logger
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import (
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"fmt"
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"io"
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"log/slog"
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"os"
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)
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// Logger is a thin wrapper around *slog.Logger.
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// All slog methods (Info, Error, Debug, Warn, …) are available via embedding.
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type Logger struct {
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*slog.Logger
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}
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// New creates a JSON logger writing to stderr for the given level string.
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// Valid levels: debug, info, warn, error.
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func New(level string) (*Logger, error) {
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lvl, err := parseLevel(level)
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if err != nil {
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return nil, err
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}
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h := slog.NewJSONHandler(os.Stderr, &slog.HandlerOptions{Level: lvl})
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return &Logger{slog.New(h)}, nil
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}
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// NewDevelopment creates a human-friendly text logger writing to stderr.
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// Use this in local dev; prefer New() in any deployed environment.
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func NewDevelopment() *Logger {
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h := slog.NewTextHandler(os.Stderr, &slog.HandlerOptions{Level: slog.LevelDebug})
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return &Logger{slog.New(h)}
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}
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// NewNop returns a no-op logger. Useful in tests that don't care about logs.
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func NewNop() *Logger {
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return &Logger{slog.New(slog.NewTextHandler(io.Discard, nil))}
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}
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// WithField returns a child logger that always includes key=value in every log line.
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func (l *Logger) WithField(key string, value any) *Logger {
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return &Logger{l.Logger.With(key, value)}
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}
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// WithFields returns a child logger enriched with every key/value in fields.
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// Prefer WithField for one or two fields; use WithFields for structured context
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// objects (e.g. attaching a request span).
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func (l *Logger) WithFields(fields map[string]any) *Logger {
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args := make([]any, 0, len(fields)*2)
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for k, v := range fields {
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args = append(args, k, v)
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}
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return &Logger{l.Logger.With(args...)}
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}
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// ── helpers ───────────────────────────────────────────────────────────────────
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func parseLevel(level string) (slog.Level, error) {
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var lvl slog.Level
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if err := lvl.UnmarshalText([]byte(level)); err != nil {
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return lvl, fmt.Errorf("logger: unknown level %q (use debug|info|warn|error)", level)
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}
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return lvl, nil
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}
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