improve attributes mover

src/html_presets_processor.py

@@ -27,8 +27,14 @@ class HtmlPresetsProcessor:
             kwargs["rule"]["tag_to_wrap"]))
 
     @staticmethod
-    def _decompose_tag(**kwargs):
-        kwargs["tag"].parent.attrs.update(kwargs["tag"].attrs)
+    def set_attrs_to_parent(tag, parent_tag):
+        for key in tag.attrs:
+            if key not in parent_tag.attrs:
+                parent_tag.attrs[key] = tag.attrs[key]
+
+    def _decompose_tag(self, **kwargs):
+        if kwargs["tag"].parent:
+            self.set_attrs_to_parent(kwargs["tag"], kwargs["tag"].parent)
         kwargs["tag"].decompose()
 
     @staticmethod
@@ -111,9 +117,9 @@ class HtmlPresetsProcessor:
         elif attr:
             del kwargs["tag"][attr]
 
-    @staticmethod
-    def _unwrap_tag(**kwargs):
-        kwargs["tag"].parent.attrs.update(kwargs["tag"].attrs)
+    def _unwrap_tag(self, **kwargs):
+        if kwargs["tag"].parent:
+            self.set_attrs_to_parent(kwargs["tag"], kwargs["tag"].parent)
         kwargs["tag"].unwrap()
 
     @staticmethod