Backport PR #42622: BUG: Styler.set_sticky not handling display of index names. 1/2 (#42695)

meeseeksmachine · attack68 · web-flow · commit a6ddae7b8106 · 2021-07-24T09:21:12.000+01:00
Co-authored-by: attack68 &lt;24256554+attack68@users.noreply.github.com&gt;
diff --git a/doc/source/whatsnew/v1.3.1.rst b/doc/source/whatsnew/v1.3.1.rst
@@ -38,6 +38,7 @@ Bug fixes
 ~~~~~~~~~
 - Fixed bug in :meth:`DataFrame.transpose` dropping values when the DataFrame had an Extension Array dtype and a duplicate index (:issue:`42380`)
 - Fixed bug in :meth:`DataFrame.to_xml` raising ``KeyError`` when called with ``index=False`` and an offset index (:issue:`42458`)
+- Fixed bug in :meth:`.Styler.set_sticky` not handling index names correctly for single index columns case (:issue:`42537`)
 - Fixed bug in :meth:`DataFrame.copy` failing to consolidate blocks in the result (:issue:`42579`)
 
 .. ---------------------------------------------------------------------------
diff --git a/pandas/io/formats/style.py b/pandas/io/formats/style.py
@@ -1452,14 +1452,25 @@ def set_sticky(
             Whether to make the index or column headers sticky.
         pixel_size : int, optional
             Required to configure the width of index cells or the height of column
-            header cells when sticking a MultiIndex. Defaults to 75 and 25 respectively.
+            header cells when sticking a MultiIndex (or with a named Index).
+            Defaults to 75 and 25 respectively.
         levels : list of int
             If ``axis`` is a MultiIndex the specific levels to stick. If ``None`` will
             stick all levels.
 
         Returns
         -------
         self : Styler
+
+        Notes
+        -----
+        This method uses the CSS 'position: sticky;' property to display. It is
+        designed to work with visible axes, therefore both:
+
+          - `styler.set_sticky(axis="index").hide_index()`
+          - `styler.set_sticky(axis="columns").hide_columns()`
+
+        may produce strange behaviour due to CSS controls with missing elements.
         """
         if axis in [0, "index"]:
             axis, obj, tag, pos = 0, self.data.index, "tbody", "left"
@@ -1471,15 +1482,42 @@ def set_sticky(
             raise ValueError("`axis` must be one of {0, 1, 'index', 'columns'}")
 
         if not isinstance(obj, pd.MultiIndex):
-            return self.set_table_styles(
-                [
+            # handling MultiIndexes requires different CSS
+            props = "position:sticky; background-color:white;"
+
+            if axis == 1:
+                # stick the first <tr> of <head> and, if index names, the second <tr>
+                # if self._hide_columns then no <thead><tr> here will exist: no conflict
+                styles: CSSStyles = [
                     {
-                        "selector": f"{tag} th",
-                        "props": f"position:sticky; {pos}:0px; background-color:white;",
+                        "selector": "thead tr:first-child",
+                        "props": props + "top:0px; z-index:2;",
                     }
-                ],
-                overwrite=False,
-            )
+                ]
+                if not self.index.names[0] is None:
+                    styles[0]["props"] = (
+                        props + f"top:0px; z-index:2; height:{pixel_size}px;"
+                    )
+                    styles.append(
+                        {
+                            "selector": "thead tr:nth-child(2)",
+                            "props": props
+                            + f"top:{pixel_size}px; z-index:2; height:{pixel_size}px; ",
+                        }
+                    )
+            else:
+                # stick the first <th> of each <tr> in both <thead> and <tbody>
+                # if self._hide_index then no <th> will exist in <tbody>: no conflict
+                # but <th> will exist in <thead>: conflict with initial element
+                styles = [
+                    {
+                        "selector": "tr th:first-child",
+                        "props": props + "left:0px; z-index:1;",
+                    }
+                ]
+
+            return self.set_table_styles(styles, overwrite=False)
+
         else:
             range_idx = list(range(obj.nlevels))
 
diff --git a/pandas/tests/io/formats/style/test_html.py b/pandas/tests/io/formats/style/test_html.py
@@ -272,17 +272,35 @@ def test_caption_as_sequence(styler):
 
 @pytest.mark.parametrize("index", [False, True])
 @pytest.mark.parametrize("columns", [False, True])
-def test_sticky_basic(styler, index, columns):
+@pytest.mark.parametrize("index_name", [True, False])
+def test_sticky_basic(styler, index, columns, index_name):
+    if index_name:
+        styler.index.name = "some text"
     if index:
         styler.set_sticky(axis=0)
     if columns:
         styler.set_sticky(axis=1)
 
     res = styler.set_uuid("").to_html()
-    cs1 = "tbody th {\n  position: sticky;\n  left: 0px;\n  background-color: white;\n}"
-    assert (cs1 in res) is index
-    cs2 = "thead th {\n  position: sticky;\n  top: 0px;\n  background-color: white;\n}"
-    assert (cs2 in res) is columns
+
+    css_for_index = (
+        "tr th:first-child {\n  position: sticky;\n  background-color: white;\n  "
+        "left: 0px;\n  z-index: 1;\n}"
+    )
+    assert (css_for_index in res) is index
+
+    css_for_cols_1 = (
+        "thead tr:first-child {\n  position: sticky;\n  background-color: white;\n  "
+        "top: 0px;\n  z-index: 2;\n"
+    )
+    css_for_cols_1 += "  height: 25px;\n}" if index_name else "}"
+    assert (css_for_cols_1 in res) is columns
+
+    css_for_cols_2 = (
+        "thead tr:nth-child(2) {\n  position: sticky;\n  background-color: white;\n  "
+        "top: 25px;\n  z-index: 2;\n  height: 25px;\n}"
+    )
+    assert (css_for_cols_2 in res) is (index_name and columns)
 
 
 @pytest.mark.parametrize("index", [False, True])
