Refactor helper function for hideable parent container and add tests

vizro-core/src/vizro/models/_dashboard.py

@@ -2,7 +2,7 @@
 
 import logging
 from functools import partial
-from typing import TYPE_CHECKING, List, Literal
+from typing import TYPE_CHECKING, List, Literal, Optional
 
 import dash
 import dash_bootstrap_components as dbc
@@ -31,12 +31,12 @@
 # TODO: Use IDs instead of className and remove className
 
 
-def _get_parent_container(children: List[html.Div], parent_id: str):
+def _get_hideable_parent_div(children: List[html.Div], parent_id: Optional[str] = None):
     """Hides the parent container if all the children containers are either hidden or None."""
     return (
-        html.Div(children=children, id=parent_id)
-        if all(getattr(div, "hidden", False) or None for div in children)
-        else html.Div(id=parent_id, hidden=True)
+        html.Div(id=parent_id, hidden=True)
+        if all(div is None or getattr(div, "hidden", False) for div in children)
+        else html.Div(children=children, id=parent_id)
     )
 
 
@@ -147,13 +147,13 @@ def _arrange_page_divs(self, page_divs: html.Div):
         left_header_divs = [page_divs["dashboard-title"]]
         left_sidebar_divs = [page_divs["nav_bar_outer"]]
         left_main_divs = [
-            _get_parent_container(children=left_header_divs, parent_id="left-header"),
+            _get_hideable_parent_div(children=left_header_divs, parent_id="left-header"),
             page_divs["nav_panel_outer"],
             page_divs["control_panel_outer"],
         ]
 
-        left_sidebar = _get_parent_container(children=left_sidebar_divs, parent_id="left-sidebar")
-        left_main = _get_parent_container(children=left_main_divs, parent_id="left-main")
+        left_sidebar = _get_hideable_parent_div(children=left_sidebar_divs, parent_id="left-sidebar")
+        left_main = _get_hideable_parent_div(children=left_main_divs, parent_id="left-main")
         left_side = html.Div(children=[left_sidebar, left_main], className="left_side", id="left_side_outer")
 
         right_header = html.Div(

vizro-core/tests/unit/vizro/models/test_dashboard.py

@@ -16,6 +16,7 @@
 import vizro
 import vizro.models as vm
 from vizro.actions._action_loop._action_loop import ActionLoop
+from vizro.models._dashboard import _get_hideable_parent_div
 
 
 @pytest.fixture()
@@ -173,3 +174,26 @@ def test_dashboard_build(self, dashboard_container, prebuilt_two_page_dashboard)
         result = json.loads(json.dumps(prebuilt_two_page_dashboard.build(), cls=plotly.utils.PlotlyJSONEncoder))
         expected = json.loads(json.dumps(dashboard_container, cls=plotly.utils.PlotlyJSONEncoder))
         assert result == expected
+
+
+@pytest.mark.parametrize(
+    "children",
+    [
+        [html.Div(hidden=False)],
+        [html.Div(id="children-id")],
+        [html.Div(hidden=True), None, html.Div(hidden=False)],
+        [html.Div(hidden=True), None, html.Div(id="children-id")],
+    ],
+)
+def test_get_hideable_parent_div_visible(children):
+    parent = _get_hideable_parent_div(children=children, parent_id="parent-id")
+    assert parent.id == "parent-id"
+    assert parent.children == children
+    assert getattr(parent, "hidden", False) is False
+
+
+@pytest.mark.parametrize("children", [[html.Div(hidden=True)], [None], [html.Div(hidden=True), None]])
+def test_get_hideable_parent_div_hidden(children):
+    parent = _get_hideable_parent_div(children=children, parent_id="parent-id")
+    assert parent.id == "parent-id"
+    assert getattr(parent, "hidden", False) is True