BUG: overriden methods of subclasses of Styler are not called during rendering pandas-dev#52728 (pandas-dev#52919)

* use type() instead of __class__

* add test

* remove unnecessary file

* typo

* revert change to class method

---------

Co-authored-by: Nicklaus Roach <[email protected]>
Co-authored-by: Nicklaus Roach <[email protected]>

Author: 3 people

doc/source/whatsnew/v2.1.0.rst

@@ -419,7 +419,7 @@ ExtensionArray
 
 Styler
 ^^^^^^
--
+- Bug in :meth:`Styler._copy` calling overridden methods in subclasses of :class:`Styler` (:issue:`52728`)
 -
 
 Other

pandas/io/formats/style.py

@@ -1579,8 +1579,8 @@ def _copy(self, deepcopy: bool = False) -> Styler:
           - applied styles (_todo)
 
         """
-        # GH 40675
-        styler = Styler(
+        # GH 40675, 52728
+        styler = type(self)(
             self.data,  # populates attributes 'data', 'columns', 'index' as shallow
         )
         shallow = [  # simple string or boolean immutables

pandas/tests/io/formats/style/test_style.py

@@ -313,6 +313,20 @@ def test_copy(comprehensive, render, deepcopy, mi_styler, mi_styler_comp):
                 assert id(getattr(s2, attr)) != id(getattr(styler, attr))
 
 
+@pytest.mark.parametrize("deepcopy", [True, False])
+def test_inherited_copy(mi_styler, deepcopy):
+    # Ensure that the inherited class is preserved when a Styler object is copied.
+    # GH 52728
+    class CustomStyler(Styler):
+        pass
+
+    custom_styler = CustomStyler(mi_styler.data)
+    custom_styler_copy = (
+        copy.deepcopy(custom_styler) if deepcopy else copy.copy(custom_styler)
+    )
+    assert isinstance(custom_styler_copy, CustomStyler)
+
+
 def test_clear(mi_styler_comp):
     # NOTE: if this test fails for new features then 'mi_styler_comp' should be updated
     # to ensure proper testing of the 'copy', 'clear', 'export' methods with new feature