fix: handle any type that implements error interface

handler.go

@@ -77,7 +77,10 @@ const (
 	ansiBrightRedFaint = "\033[91;2m"
 )
 
-const errKey = "err"
+const (
+	errKey = "err"
+	badKey = "!BADKEY"
+)
 
 var (
 	defaultLevel      = slog.LevelInfo
@@ -345,7 +348,7 @@ func (h *handler) appendAttr(buf *buffer, attr slog.Attr, groupsPrefix string, g
 		}
 	} else if err, ok := attr.Value.Any().(tintError); ok {
 		// append tintError
-		h.appendTintError(buf, err, groupsPrefix)
+		h.appendTintError(buf, err, attr.Key, groupsPrefix)
 		buf.WriteByte(' ')
 	} else {
 		h.appendKey(buf, attr.Key, groupsPrefix)
@@ -395,9 +398,12 @@ func (h *handler) appendValue(buf *buffer, v slog.Value, quote bool) {
 	}
 }
 
-func (h *handler) appendTintError(buf *buffer, err error, groupsPrefix string) {
+func (h *handler) appendTintError(buf *buffer, err error, key string, groupsPrefix string) {
+	if key == badKey {
+		key = errKey
+	}
 	buf.WriteStringIf(!h.noColor, ansiBrightRedFaint)
-	appendString(buf, groupsPrefix+errKey, true)
+	appendString(buf, groupsPrefix+key, true)
 	buf.WriteByte('=')
 	buf.WriteStringIf(!h.noColor, ansiResetFaint)
 	appendString(buf, err.Error(), true)
@@ -424,15 +430,12 @@ func needsQuoting(s string) bool {
 	return false
 }
 
-type tintError struct{ error }
+type tintError interface{ Error() string }
 
 // Err returns a tinted (colorized) [slog.Attr] that will be written in red color
 // by the [tint.Handler]. When used with any other [slog.Handler], it behaves as
 //
 //	slog.Any("err", err)
 func Err(err error) slog.Attr {
-	if err != nil {
-		err = tintError{err}
-	}
 	return slog.Any(errKey, err)
 }

handler_test.go

@@ -27,7 +27,7 @@ func Example() {
 	slog.Info("Starting server", "addr", ":8080", "env", "production")
 	slog.Debug("Connected to DB", "db", "myapp", "host", "localhost:5432")
 	slog.Warn("Slow request", "method", "GET", "path", "/users", "duration", 497*time.Millisecond)
-	slog.Error("DB connection lost", tint.Err(errors.New("connection reset")), "db", "myapp")
+	slog.Error("DB connection lost", errors.New("connection reset"), "db", "myapp")
 	// Output:
 }
 
@@ -52,13 +52,13 @@ func TestHandler(t *testing.T) {
 		},
 		{
 			F: func(l *slog.Logger) {
-				l.Error("test", tint.Err(errors.New("fail")))
+				l.Error("test", errors.New("fail"))
 			},
 			Want: `Nov 10 23:00:00.000 ERR test err=fail`,
 		},
 		{
 			F: func(l *slog.Logger) {
-				l.Info("test", slog.Group("group", slog.String("key", "val"), tint.Err(errors.New("fail"))))
+				l.Info("test", slog.Group("group", slog.String("key", "val"), errors.New("fail")))
 			},
 			Want: `Nov 10 23:00:00.000 INF test group.key=val group.err=fail`,
 		},
@@ -331,7 +331,7 @@ func TestHandler(t *testing.T) {
 		{ // https://github.com/lmittmann/tint/issues/44
 			F: func(l *slog.Logger) {
 				l = l.WithGroup("group")
-				l.Error("test", tint.Err(errTest))
+				l.Error("test", errTest)
 			},
 			Want: `Nov 10 23:00:00.000 ERR test group.err=fail`,
 		},
@@ -401,6 +401,10 @@ func TestReplaceAttr(t *testing.T) {
 
 	replaceAttrRecorder := func(record *[]replaceAttrParams) func([]string, slog.Attr) slog.Attr {
 		return func(groups []string, a slog.Attr) slog.Attr {
+			// Ignore time since it will be necessarily different when logged at different times
+			if a.Key == "time" {
+				return slog.Attr{}
+			}
 			*record = append(*record, replaceAttrParams{groups, a})
 			return a
 		}