Write utility for logging

utils/logger.go

@@ -0,0 +1,98 @@
+package utils
+
+import (
+	"context"
+	"log/slog"
+	"os"
+	"path/filepath"
+
+	"github.com/mdobak/go-xerrors"
+)
+
+type stackFrame struct {
+	Func   string `json:"func"`
+	Source string `json:"source"`
+	Line   int    `json:"line"`
+}
+
+func replaceAttr(_ []string, a slog.Attr) slog.Attr {
+	switch a.Value.Kind() {
+	case slog.KindAny:
+		switch v := a.Value.Any().(type) {
+		case error:
+			a.Value = fmtErr(v)
+		}
+	}
+
+	return a
+}
+
+// marshalStack extracts stack frames from the error
+func marshalStack(err error) []stackFrame {
+	trace := xerrors.StackTrace(err)
+
+	if len(trace) == 0 {
+		return nil
+	}
+
+	frames := trace.Frames()
+
+	s := make([]stackFrame, len(frames))
+
+	for i, v := range frames {
+		f := stackFrame{
+			Source: filepath.Join(
+				filepath.Base(filepath.Dir(v.File)),
+				filepath.Base(v.File),
+			),
+			Func: filepath.Base(v.Function),
+			Line: v.Line,
+		}
+
+		s[i] = f
+	}
+
+	return s
+}
+
+// fmtErr returns a slog.Value with keys `msg` and `trace`. If the error
+// does not implement interface { StackTrace() errors.StackTrace }, the `trace`
+// key is omitted.
+func fmtErr(err error) slog.Value {
+	var groupValues []slog.Attr
+
+	groupValues = append(groupValues, slog.String("msg", err.Error()))
+
+	frames := marshalStack(err)
+
+	if frames != nil {
+		groupValues = append(groupValues,
+			slog.Any("trace", frames),
+		)
+	}
+
+	return slog.GroupValue(groupValues...)
+}
+
+func GetLogger() *slog.Logger {
+	h := slog.NewJSONHandler(os.Stdout, &slog.HandlerOptions{
+		ReplaceAttr: replaceAttr,
+	})
+
+	logger := slog.New(h)
+	return logger
+}
+
+func main() {
+	h := slog.NewJSONHandler(os.Stdout, &slog.HandlerOptions{
+		ReplaceAttr: replaceAttr,
+	})
+
+	logger := slog.New(h)
+
+	ctx := context.Background()
+
+	err := xerrors.New("something happened")
+
+	logger.ErrorContext(ctx, "image uploaded", slog.Any("error", err))
+}