Added Options.AddSource (#14)

* added `Options.AddSource`

* improved doc & minor refactoring

---------

Co-authored-by: lmittmann <[email protected]>

README.md

@@ -13,6 +13,8 @@
 
 Package `tint` provides a [`slog.Handler`](https://pkg.go.dev/golang.org/x/exp/slog#Handler) that writes tinted logs. The output format is inspired by the `zerolog.ConsoleWriter`.
 
+The output format can be customized using [`Options`](https://pkg.go.dev/github.com/lmittmann/tint#Options) which is a drop-in replacement for [`slog.HandlerOptions`](https://pkg.go.dev/golang.org/x/exp/slog#HandlerOptions).
+
 ```
 go get github.com/lmittmann/tint
 ```

handler.go

@@ -2,6 +2,9 @@
 Package tint provides a [slog.Handler] that writes tinted logs. The output
 format is inspired by the [zerolog.ConsoleWriter].
 
+The output format can be customized using [Options], which is a drop-in
+replacement for [slog.HandlerOptions].
+
 [zerolog.ConsoleWriter]: https://pkg.go.dev/github.com/rs/zerolog#ConsoleWriter
 */
 package tint
@@ -11,6 +14,8 @@ import (
 	"encoding"
 	"fmt"
 	"io"
+	"path/filepath"
+	"runtime"
 	"strconv"
 	"sync"
 	"time"
@@ -32,37 +37,49 @@ const (
 
 const keyErr = "err"
 
-var defaultTimeFormat = time.StampMilli
+var (
+	defaultTimeFormat = time.StampMilli
+	defaultLevel      = slog.LevelInfo
+)
 
 // Options for a slog.Handler that writes tinted logs. A zero Options consists
 // entirely of default values.
+//
+// Options can be used as a drop-in replacement for [slog.HandlerOptions].
 type Options struct {
+	// Enable source code location (Default: false)
+	AddSource bool
+
 	// Minimum level to log (Default: slog.LevelInfo)
-	Level slog.Level
+	Level slog.Leveler
+
+	// ReplaceAttr is called to rewrite each non-group attribute before it is logged.
+	// See https://pkg.go.dev/golang.org/x/exp/slog#HandlerOptions for details.
+	ReplaceAttr func(groups []string, attr slog.Attr) slog.Attr
 
 	// Time format (Default: time.StampMilli)
 	TimeFormat string
 
 	// Disable color (Default: false)
 	NoColor bool
-
-	// ReplaceAttr is called to rewrite each non-group attribute before it is logged.
-	// See https://pkg.go.dev/golang.org/x/exp/slog#HandlerOptions for details.
-	ReplaceAttr func(groups []string, attr slog.Attr) slog.Attr
 }
 
 // NewHandler creates a [slog.Handler] that writes tinted logs to Writer w with
 // the given options.
 func (opts Options) NewHandler(w io.Writer) slog.Handler {
 	h := &handler{
 		w:           w,
-		level:       opts.Level,
-		timeFormat:  opts.TimeFormat,
-		noColor:     opts.NoColor,
+		addSource:   opts.AddSource,
+		level:       defaultLevel,
 		replaceAttr: opts.ReplaceAttr,
+		timeFormat:  defaultTimeFormat,
+		noColor:     opts.NoColor,
 	}
-	if h.timeFormat == "" {
-		h.timeFormat = defaultTimeFormat
+	if opts.Level != nil {
+		h.level = opts.Level.Level()
+	}
+	if opts.TimeFormat != "" {
+		h.timeFormat = opts.TimeFormat
 	}
 	return h
 }
@@ -80,12 +97,13 @@ type handler struct {
 	groupsSlice []string
 
 	mu sync.Mutex
-	w  io.Writer // Output writer
+	w  io.Writer
 
-	level       slog.Level // Minimum level to log (Default: slog.LevelInfo)
-	timeFormat  string     // Time format (Default: time.StampMilli)
-	noColor     bool       // Disable color (Default: false)
+	addSource   bool
+	level       slog.Level
 	replaceAttr func([]string, slog.Attr) slog.Attr
+	timeFormat  string
+	noColor     bool
 }
 
 func (h *handler) clone() *handler {
@@ -94,10 +112,11 @@ func (h *handler) clone() *handler {
 		groups:      h.groups,
 		groupsSlice: h.groupsSlice,
 		w:           h.w,
+		addSource:   h.addSource,
 		level:       h.level,
+		replaceAttr: h.replaceAttr,
 		timeFormat:  h.timeFormat,
 		noColor:     h.noColor,
-		replaceAttr: h.replaceAttr,
 	}
 }
 
@@ -141,6 +160,21 @@ func (h *handler) Handle(_ context.Context, r slog.Record) error {
 		buf.WriteByte(' ')
 	}
 
+	// write source
+	if h.addSource {
+		fs := runtime.CallersFrames([]uintptr{r.PC})
+		f, _ := fs.Next()
+		if f.File != "" {
+			if rep == nil {
+				h.appendSource(buf, f)
+				buf.WriteByte(' ')
+			} else if a := rep(h.groupsSlice, slog.Any(slog.SourceKey, f)); a.Key != "" {
+				appendValue(buf, a.Value, false)
+				buf.WriteByte(' ')
+			}
+		}
+	}
+
 	// write message
 	if rep == nil {
 		buf.WriteString(r.Message)
@@ -242,6 +276,16 @@ func (h *handler) appendLevel(buf *buffer, level slog.Level) {
 	}
 }
 
+func (h *handler) appendSource(buf *buffer, f runtime.Frame) {
+	dir, file := filepath.Split(f.File)
+
+	buf.WriteStringIf(!h.noColor, ansiFaint)
+	buf.WriteString(filepath.Join(filepath.Base(dir), file))
+	buf.WriteByte(':')
+	buf.WriteString(strconv.Itoa(f.Line))
+	buf.WriteStringIf(!h.noColor, ansiReset)
+}
+
 func (h *handler) appendAttr(buf *buffer, attr slog.Attr, groups string) {
 	if attr.Key == "" {
 		return

handler_test.go

@@ -91,6 +91,15 @@ func TestHandler(t *testing.T) {
 			},
 			Want: `Nov 11 00:00:00.000 INF test slice="[a b c]" map="map[a:1 b:2 c:3]"`,
 		},
+		{
+			Opts: tint.Options{
+				AddSource: true,
+			},
+			F: func(l *slog.Logger) {
+				l.Info("test", "key", "val")
+			},
+			Want: `Nov 11 00:00:00.000 INF tint/handler_test.go:99 test key=val`,
+		},
 		{
 			Opts: tint.Options{
 				TimeFormat: time.Kitchen,