log: Add File method (#50)

log/log.go

@@ -5,12 +5,17 @@ import (
 	"io"
 	"log"
 	"log/slog"
+	"os"
 )
 
-var std = newLogger(log.Default(), nil)
+var std = newLogger(log.Default(), os.Stderr)
 
 func Default() *Logger { return std }
 
+func File() string {
+	return std.File()
+}
+
 func SetOutput(file string, extra io.Writer) {
 	std.SetOutput(file, extra)
 }

log/logger.go

@@ -50,6 +50,13 @@ func New(file, prefix string, flag int) *Logger {
 	return newLogger(log.New(f, prefix, flag), f)
 }
 
+func (l *Logger) File() string {
+	if l.file != nil {
+		return l.file.Name()
+	}
+	return ""
+}
+
 func (l *Logger) setOutput(file *os.File, extra io.Writer) {
 	var writers []io.Writer
 	if file != nil {

log/logger_test.go

@@ -11,12 +11,18 @@ import (
 func TestLogger(t *testing.T) {
 	logger := New("test1", "", 0)
 	defer os.Remove("test1")
+	if file := logger.File(); file != "test1" {
+		t.Errorf("expected test1; got %q", file)
+	}
 	logger.Print("test1")
 	if err := os.Rename("test1", "test2"); err != nil {
 		t.Fatal(err)
 	}
 	defer os.Remove("test2")
 	logger.Rotate()
+	if file := logger.File(); file != "test1" {
+		t.Errorf("expected test1; got %q", file)
+	}
 	logger.Print("test2")
 	b1, err := os.ReadFile("test1")
 	if err != nil {
@@ -27,16 +33,19 @@ func TestLogger(t *testing.T) {
 		t.Fatal(err)
 	}
 	if s := string(b1); s != "test2\n" {
-		t.Errorf("expected test2; got %s", s)
+		t.Errorf("expected test2; got %q", s)
 	}
 	if s := string(b2); s != "test1\n" {
-		t.Errorf("expected test1; got %s", s)
+		t.Errorf("expected test1; got %q", s)
 	}
 }
 
 func TestSLogger(t *testing.T) {
 	var buf bytes.Buffer
 	l := newLogger(log.New(&buf, "", 0), nil)
+	if file := l.File(); file != "" {
+		t.Errorf("expected empty string; got %q", file)
+	}
 	l.Info("test")
 	if s, expected := buf.String(), "INFO test\n"; s != expected {
 		t.Errorf("expected %q; got %q", expected, s)