Fixed wrong group prefix for error attribute (#45)

* added test case

* fixed #44

---------

Co-authored-by: lmittmann <lmittmann@users.noreply.github.com>

handler.go

@@ -400,9 +400,9 @@ func (h *handler) appendValue(buf *buffer, v slog.Value, quote bool) {
 	}
 }
 
-func (h *handler) appendTintError(buf *buffer, err error, groups string) {
+func (h *handler) appendTintError(buf *buffer, err error, groupsPrefix string) {
 	buf.WriteStringIf(!h.noColor, ansiBrightRedFaint)
-	appendString(buf, h.groupPrefix+groups+errKey, true)
+	appendString(buf, groupsPrefix+errKey, true)
 	buf.WriteByte('=')
 	buf.WriteStringIf(!h.noColor, ansiResetFaint)
 	appendString(buf, err.Error(), true)

handler_test.go

@@ -327,6 +327,13 @@ func TestHandler(t *testing.T) {
 			},
 			Want: `Nov 10 23:00:00.000 INF tint/handler_test.go:326 test`,
 		},
+		{ // https://github.com/lmittmann/tint/issues/44
+			F: func(l *slog.Logger) {
+				l = l.WithGroup("group")
+				l.Error("test", tint.Err(errTest))
+			},
+			Want: `Nov 10 23:00:00.000 ERR test group.err=fail`,
+		},
 	}
 
 	for i, test := range tests {