Adopt `classname` instead of `classnames` in all MenuItem/Sidebar usage

- Adds a deprecation path, including documentation to further remove unpredictable naming of adding `classname` in Python APIs
- Intentionally keeps `classNames` in Telepath adaptor inner usage as this convention is not set, however, the server side value passed in will use `classname`
- See https://docs.wagtail.org/en/stable/contributing/general_guidelines.html#use-classname-in-python-html-template-tag-variables
- See #9769 & #9770

CHANGELOG.txt

@@ -77,6 +77,7 @@ Changelog
  * Maintenance: Optimise `lru_cache` usage (Jake Howard)
  * Maintenance: Implement `date_since` in `get_most_popular` inside `search_promotions.models.Query` (TopDevPros)
  * Maintenance: Refactor generic view subclasses to better reuse the generic templates and breadcrumbs (Sage Abdullah)
+ * Maintenance: Adopt consistent `classname` (not `classnames`) attributes for all `MenuItem` usage, including deprecation warnings (LB (Ben) Johnston)
 
 
 5.1.3 (xx.xx.20xx) - IN DEVELOPMENT

client/src/components/Sidebar/menu/ActionMenuItem.tsx

@@ -83,7 +83,7 @@ export class ActionMenuItemDefinition implements MenuItemDefinition {
     action,
     attrs,
     icon_name: iconName = null,
-    classnames = undefined,
+    classname = undefined,
     method = 'POST',
   }) {
     this.name = name;
@@ -91,7 +91,7 @@ export class ActionMenuItemDefinition implements MenuItemDefinition {
     this.action = action;
     this.attrs = attrs;
     this.iconName = iconName;
-    this.classNames = classnames;
+    this.classNames = classname;
     this.method = method;
   }
 

client/src/components/Sidebar/menu/LinkMenuItem.tsx

@@ -98,14 +98,14 @@ export class LinkMenuItemDefinition implements MenuItemDefinition {
     url,
     attrs,
     icon_name: iconName = null,
-    classnames = undefined,
+    classname = undefined,
   }) {
     this.name = name;
     this.label = label;
     this.url = url;
     this.attrs = attrs;
     this.iconName = iconName;
-    this.classNames = classnames;
+    this.classNames = classname;
   }
 
   render({ path, slim, state, dispatch, navigate }) {

client/src/components/Sidebar/menu/PageExplorerMenuItem.tsx

@@ -122,11 +122,11 @@ export class PageExplorerMenuItemDefinition extends LinkMenuItemDefinition {
       url,
       attrs,
       icon_name: iconName = null,
-      classnames = undefined,
+      classname = undefined,
     },
     startPageId: number,
   ) {
-    super({ name, label, url, attrs, icon_name: iconName, classnames });
+    super({ name, label, url, attrs, icon_name: iconName, classname });
     this.startPageId = startPageId;
   }
 

client/src/components/Sidebar/menu/SubMenuItem.tsx

@@ -170,7 +170,7 @@ export class SubMenuItemDefinition implements MenuItemDefinition {
       label,
       attrs,
       icon_name: iconName = null,
-      classnames = undefined,
+      classname = undefined,
       footer_text: footerText = '',
     }: any,
     menuItems: MenuItemDefinition[],
@@ -180,7 +180,7 @@ export class SubMenuItemDefinition implements MenuItemDefinition {
     this.menuItems = menuItems;
     this.attrs = attrs;
     this.iconName = iconName;
-    this.classNames = classnames;
+    this.classNames = classname;
     this.footerText = footerText;
   }
 

docs/reference/hooks.md

@@ -244,8 +244,12 @@ Add an item to the Wagtail admin menu. The callable passed to this hook must ret
 
 -   `name` - an internal name used to identify the menu item; defaults to the slugified form of the label.
 -   `icon_name` - icon to display against the menu item; no defaults, optional, but should be set for top-level menu items so they can be identified when collapsed.
--   `classnames` - additional classnames applied to the link
--   `order` - an integer which determines the item's position in the menu
+-   `classname` - additional classes applied to the link.
+-   `order` - an integer which determines the item's position in the menu.
+
+```{versionchanged} 5.2
+Use `classname` as the `classnames` keyword argument is deprecated and will be removed in a future release.
+```
 
 For menu items that are only available to superusers, the subclass `wagtail.admin.menu.AdminOnlyMenuItem` can be used in place of `MenuItem`.
 
@@ -337,11 +341,15 @@ Add an item to the Wagtail admin search "Other Searches". Behaviour of this hook
 -   `label` - text displayed in the "Other Searches" option box.
 -   `name` - an internal name used to identify the search option; defaults to the slugified form of the label.
 -   `url` - the URL of the target search page.
--   `classnames` - arbitrary CSS classnames applied to the link
+-   `classname` - additional CSS classes applied to the link.
 -   `icon_name` - icon to display next to the label.
 -   `attrs` - additional HTML attributes to apply to the link.
 -   `order` - an integer which determines the item's position in the list of options.
 
+```{versionchanged} 5.2
+Use `classname` as the `classnames` keyword argument is deprecated and will be removed in a future release.
+```
+
 Setting the URL can be achieved using reverse() on the target search page. The GET parameter 'q' will be appended to the given URL.
 
 A template tag, `search_other` is provided by the `wagtailadmin_tags` template module. This tag takes a single, optional parameter, `current`, which allows you to specify the `name` of the search option currently active. If the parameter is not given, the hook defaults to a reverse lookup of the page's URL for comparison against the `url` parameter.

docs/releases/5.2.md

@@ -98,6 +98,7 @@ depth: 1
  * Optimise `lru_cache` usage (Jake Howard)
  * Implement `date_since`` in `get_most_popular`` inside `search_promotions.models.Query (TopDevPros)
  * Refactor generic view subclasses to better reuse the generic templates and breadcrumbs (Sage Abdullah)
+ * Adopt consistent `classname` (not `classnames`) attributes for all `MenuItem` usage, including deprecation warnings (LB (Ben) Johnston)
 
 
 ## Upgrade considerations - changes affecting all projects
@@ -108,6 +109,44 @@ depth: 1
 
 Wagtail now uses the Willow feature of providing the image MIME type, which uses the [`filetype`](https://pypi.org/project/filetype/) package.
 
+### Adoption of `classname` convention for `MenuItem` related classes and hooks
+
+Wagtail `MenuItem` and menu hooks have been updated to use the more consistent naming of `classname` (singular) instead of `classnames` (plural), a convention that started in Wagtail 4.2.
+
+The current `classnames` keyword argument naming will be supported, but will trigger a deprecation warning. Support for this variant will be removed in a future release.
+
+The following classes will adopt this new convention.
+
+-   `admin.menu.MenuItem`
+-   `admin.ui.sidebar.ActionMenuItem`
+-   `admin.ui.sidebar.LinkMenuItem`
+-   `admin.ui.sidebar.PageExplorerMenuItem`
+-   `contrib.settings.registry.SettingMenuItem`
+
+The following hooks usage may be impacted if `classnames` were used when generating menu items.
+
+-   `register_admin_menu_item`
+-   `register_settings_menu_item`
+
+### Example
+
+```python
+from django.urls import reverse
+
+from wagtail import hooks
+from wagtail.admin.menu import MenuItem
+
+@hooks.register('register_admin_menu_item')
+def register_frank_menu_item():
+  return MenuItem(
+    'Frank',
+    reverse('frank'),
+    icon_name='folder-inverse',
+    order=10000,
+    classname="highlight-menu" # not classnames=...
+  )
+```
+
 ## Upgrade considerations - deprecation of old functionality
 
 ## Upgrade considerations - changes affecting Wagtail customisations

wagtail/admin/menu.py

@@ -1,3 +1,5 @@
+from warnings import warn
+
 from django.core.exceptions import ImproperlyConfigured
 from django.forms import Media, MediaDefiningClass
 from django.utils.functional import cached_property
@@ -6,15 +8,29 @@ from wagtail import hooks
 from wagtail.admin.ui.sidebar import LinkMenuItem as LinkMenuItemComponent
 from wagtail.admin.ui.sidebar import SubMenuItem as SubMenuItemComponent
 from wagtail.coreutils import cautious_slugify
+from wagtail.utils.deprecation import RemovedInWagtail60Warning
 
 
 class MenuItem(metaclass=MediaDefiningClass):
     def __init__(
-        self, label, url, name=None, classnames="", icon_name="", attrs=None, order=1000
+        self,
+        label,
+        url,
+        name=None,
+        classname="",
+        classnames="",
+        icon_name="",
+        attrs=None,
+        order=1000,
     ):
+        if classnames:
+            warn(
+                "The `classnames` kwarg for MenuItem is deprecated - use `classname` instead.",
+                category=RemovedInWagtail60Warning,
+            )
         self.label = label
         self.url = url
-        self.classnames = classnames
+        self.classname = classname or classnames
         self.icon_name = icon_name
         self.name = name or cautious_slugify(str(label))
         self.attrs = attrs or {}
@@ -36,7 +52,7 @@ class MenuItem(metaclass=MediaDefiningClass):
             self.label,
             self.url,
             icon_name=self.icon_name,
-            classnames=self.classnames,
+            classname=self.classname,
             attrs=self.attrs,
         )
 
@@ -147,7 +163,7 @@ class SubmenuMenuItem(MenuItem):
             self.label,
             self.menu.render_component(request),
             icon_name=self.icon_name,
-            classnames=self.classnames,
+            classname=self.classname,
             attrs=self.attrs,
         )
 

wagtail/admin/search.py

@@ -1,3 +1,5 @@
+from warnings import warn
+
 from django.forms import Media, MediaDefiningClass
 from django.forms.utils import flatatt
 from django.template.loader import render_to_string
@@ -7,17 +9,31 @@ from django.utils.text import slugify
 
 from wagtail import hooks
 from wagtail.admin.forms.search import SearchForm
+from wagtail.utils.deprecation import RemovedInWagtail60Warning
 
 
 class SearchArea(metaclass=MediaDefiningClass):
     template = "wagtailadmin/shared/search_area.html"
 
     def __init__(
-        self, label, url, name=None, classnames="", icon_name="", attrs=None, order=1000
+        self,
+        label,
+        url,
+        name=None,
+        classname="",
+        classnames="",
+        icon_name="",
+        attrs=None,
+        order=1000,
     ):
+        if classnames:
+            warn(
+                "The `classnames` kwarg for SearchArea is deprecated - use `classname` instead.",
+                category=RemovedInWagtail60Warning,
+            )
         self.label = label
         self.url = url
-        self.classnames = classnames
+        self.classname = classname or classnames
         self.icon_name = icon_name
         self.name = name or slugify(str(label))
         self.order = order
@@ -71,7 +87,7 @@ class SearchArea(metaclass=MediaDefiningClass):
             {
                 "name": self.name,
                 "url": self.url,
-                "classnames": self.classnames,
+                "classname": self.classname,
                 "icon_name": self.icon_name,
                 "attr_string": self.attr_string,
                 "label": self.label,

wagtail/admin/templates/wagtailadmin/shared/search_area.html

@@ -1,4 +1,4 @@
 {% load wagtailadmin_tags %}
 <li>
-    <a href="{{ url }}?q={{ query_string|urlencode }}" class="{{ classnames }}{% if active %} nolink{% endif %}"{{ attr_string }}>{% if icon_name %}{% icon name=icon_name classname="filter-options__icon" %}{% endif %}{{ label }}</a>
+    <a href="{{ url }}?q={{ query_string|urlencode }}" class="{{ classname }}{% if active %} nolink{% endif %}"{{ attr_string }}>{% if icon_name %}{% icon name=icon_name classname="filter-options__icon" %}{% endif %}{{ label }}</a>
 </li>

wagtail/admin/tests/tests.py

@@ -37,13 +37,13 @@ class TestHome(WagtailTestUtils, TestCase):
         # check that custom menu items (including classname / icon_name) are pulled in
         self.assertContains(
             response,
-            '{"name": "kittens", "label": "Kittens!", "icon_name": "kitten", "classnames": "kitten--test", "attrs": {"data-is-custom": "true"}, "url": "http://www.tomroyal.com/teaandkittens/"}',
+            '{"name": "kittens", "label": "Kittens!", "icon_name": "kitten", "classname": "kitten--test", "attrs": {"data-is-custom": "true"}, "url": "http://www.tomroyal.com/teaandkittens/"}',
         )
 
         # Check that the explorer menu item is here, with the right start page.
         self.assertContains(
             response,
-            '[{"name": "explorer", "label": "Pages", "icon_name": "folder-open-inverse", "classnames": "", "attrs": {}, "url": "/admin/pages/"}, 1]',
+            '[{"name": "explorer", "label": "Pages", "icon_name": "folder-open-inverse", "classname": "", "attrs": {}, "url": "/admin/pages/"}, 1]',
         )
 
         # There should be a link to the friend admin in on the home page.
@@ -56,7 +56,7 @@ class TestHome(WagtailTestUtils, TestCase):
         response = self.client.get(reverse("wagtailadmin_home") + "?hide-kittens=true")
         self.assertNotContains(
             response,
-            '{"name": "kittens", "label": "Kittens!", "icon_name": "kitten", "classnames": "kitten--test", "attrs": {"data-is-custom": "true"}, "url": "http://www.tomroyal.com/teaandkittens/"}',
+            '{"name": "kittens", "label": "Kittens!", "icon_name": "kitten", "classname": "kitten--test", "attrs": {"data-is-custom": "true"}, "url": "http://www.tomroyal.com/teaandkittens/"}',
         )
 
     def test_dashboard_panels(self):
@@ -409,6 +409,26 @@ class TestMenuItem(WagtailTestUtils, TestCase):
         menuitem = MenuItem(_("Test"), reverse_lazy("wagtailadmin_home"))
         self.assertIs(menuitem.is_active(self.request), True)
 
+    def test_menuitem_with_classname(self):
+        menuitem = MenuItem(
+            _("Test"),
+            reverse_lazy("wagtailadmin_home"),
+            classname="highlight-item",
+        )
+        self.assertEqual(menuitem.classname, "highlight-item")
+
+    def test_menuitem_with_deprecated_classnames(self):
+        with self.assertWarnsRegex(
+            RemovedInWagtail60Warning,
+            "The `classnames` kwarg for MenuItem is deprecated - use `classname` instead.",
+        ):
+            menuitem = MenuItem(
+                _("Test"),
+                reverse_lazy("wagtailadmin_home"),
+                classnames="is-dimmed",
+            )
+        self.assertEqual(menuitem.classname, "is-dimmed")
+
 
 class TestUserPassesTestPermissionDecorator(WagtailTestUtils, TestCase):
     """

wagtail/admin/tests/ui/test_sidebar.py

@@ -14,6 +14,7 @@ from wagtail.admin.ui.sidebar import (
 )
 from wagtail.telepath import JSContext
 from wagtail.test.utils import WagtailTestUtils
+from wagtail.utils.deprecation import RemovedInWagtail60Warning
 
 
 class TestAdaptLinkMenuItem(TestCase):
@@ -26,7 +27,7 @@ class TestAdaptLinkMenuItem(TestCase):
                 "_type": "wagtail.sidebar.LinkMenuItem",
                 "_args": [
                     {
-                        "classnames": "",
+                        "classname": "",
                         "icon_name": "",
                         "label": "Link",
                         "name": "link",
@@ -44,7 +45,7 @@ class TestAdaptLinkMenuItem(TestCase):
                 "Link",
                 "/link/",
                 icon_name="link-icon",
-                classnames="some classes",
+                classname="some classes",
                 attrs={"data-is-custom": "true"},
             )
         )
@@ -55,7 +56,7 @@ class TestAdaptLinkMenuItem(TestCase):
                 "_type": "wagtail.sidebar.LinkMenuItem",
                 "_args": [
                     {
-                        "classnames": "some classes",
+                        "classname": "some classes",
                         "icon_name": "link-icon",
                         "label": "Link",
                         "name": "link",
@@ -66,6 +67,33 @@ class TestAdaptLinkMenuItem(TestCase):
             },
         )
 
+    def test_adapt_with_deprecated_classnames(self):
+
+        with self.assertWarnsRegex(
+            RemovedInWagtail60Warning,
+            "The `classnames` kwarg for sidebar LinkMenuItem is deprecated - use `classname` instead.",
+        ):
+            packed = JSContext().pack(
+                LinkMenuItem("link", "Link", "/link/", classnames="legacy-classes")
+            )
+
+        self.assertEqual(
+            packed,
+            {
+                "_type": "wagtail.sidebar.LinkMenuItem",
+                "_args": [
+                    {
+                        "classname": "legacy-classes",  # mapped to new name but raises warning
+                        "icon_name": "",
+                        "label": "Link",
+                        "name": "link",
+                        "url": "/link/",
+                        "attrs": {},
+                    }
+                ],
+            },
+        )
+
 
 class TestAdaptSubMenuItem(TestCase):
     def test_adapt(self):
@@ -89,7 +117,7 @@ class TestAdaptSubMenuItem(TestCase):
                         "name": "sub-menu",
                         "label": "Sub menu",
                         "icon_name": "",
-                        "classnames": "",
+                        "classname": "",
                         "footer_text": "Footer text",
                         "attrs": {},
                     },
@@ -101,7 +129,7 @@ class TestAdaptSubMenuItem(TestCase):
                                     "name": "link",
                                     "label": "Link",
                                     "icon_name": "link-icon",
-                                    "classnames": "",
+                                    "classname": "",
                                     "url": "/link/",
                                     "attrs": {},
                                 }
@@ -132,7 +160,7 @@ class TestAdaptSubMenuItem(TestCase):
                         "name": "sub-menu",
                         "label": "Sub menu",
                         "icon_name": "",
-                        "classnames": "",
+                        "classname": "",
                         "footer_text": "",
                         "attrs": {},
                     },
@@ -144,7 +172,7 @@ class TestAdaptSubMenuItem(TestCase):
                                     "name": "link",
                                     "label": "Link",
                                     "icon_name": "link-icon",
-                                    "classnames": "",
+                                    "classname": "",
                                     "url": "/link/",
                                     "attrs": {},
                                 }
@@ -167,7 +195,7 @@ class TestAdaptPageExplorerMenuItem(TestCase):
                 "_args": [
                     {
                         "attrs": {},
-                        "classnames": "",
+                        "classname": "",
                         "icon_name": "",
                         "label": "Pages",
                         "name": "pages",
@@ -218,7 +246,7 @@ class TestAdaptMainMenuModule(WagtailTestUtils, DjangoTestCase):
                                     "name": "pages",
                                     "label": "Pages",
                                     "icon_name": "",
-                                    "classnames": "",
+                                    "classname": "",
                                     "url": "/pages/",
                                     "attrs": {},
                                 }
@@ -233,7 +261,7 @@ class TestAdaptMainMenuModule(WagtailTestUtils, DjangoTestCase):
                                     "name": "account",
                                     "label": "Account",
                                     "icon_name": "user",
-                                    "classnames": "",
+                                    "classname": "",
                                     "url": reverse("wagtailadmin_account"),
                                     "attrs": {},
                                 }
@@ -246,7 +274,7 @@ class TestAdaptMainMenuModule(WagtailTestUtils, DjangoTestCase):
                                     "name": "logout",
                                     "label": "Logout",
                                     "icon_name": "logout",
-                                    "classnames": "",
+                                    "classname": "",
                                     "action": reverse("wagtailadmin_logout"),
                                     "method": "POST",
                                     "attrs": {},

wagtail/admin/ui/sidebar.py

@@ -1,4 +1,5 @@
 from typing import Any, List, Mapping
+from warnings import warn
 
 from django import forms
 from django.urls import reverse
@@ -6,6 +7,7 @@ from django.utils.functional import cached_property
 
 from wagtail.admin.staticfiles import versioned_static
 from wagtail.telepath import Adapter, adapter
+from wagtail.utils.deprecation import RemovedInWagtail60Warning
 
 
 class BaseSidebarAdapter(Adapter):
@@ -27,13 +29,19 @@ class MenuItem:
         name: str,
         label: str,
         icon_name: str = "",
+        classname: str = "",
         classnames: str = "",
         attrs: Mapping[str, Any] = None,
     ):
+        if classnames:
+            warn(
+                "The `classnames` kwarg for sidebar MenuItem is deprecated - use `classname` instead.",
+                category=RemovedInWagtail60Warning,
+            )
         self.name = name
         self.label = label
         self.icon_name = icon_name
-        self.classnames = classnames
+        self.classname = classname or classnames
         self.attrs = attrs or {}
 
     def js_args(self):
@@ -42,7 +50,7 @@ class MenuItem:
                 "name": self.name,
                 "label": self.label,
                 "icon_name": self.icon_name,
-                "classnames": self.classnames,
+                "classname": self.classname,
                 "attrs": self.attrs,
             }
         ]
@@ -56,14 +64,20 @@ class LinkMenuItem(MenuItem):
         label: str,
         url: str,
         icon_name: str = "",
+        classname: str = "",
         classnames: str = "",
         attrs: Mapping[str, Any] = None,
     ):
+        if classnames:
+            warn(
+                "The `classnames` kwarg for sidebar LinkMenuItem is deprecated - use `classname` instead.",
+                category=RemovedInWagtail60Warning,
+            )
         super().__init__(
             name,
             label,
             icon_name=icon_name,
-            classnames=classnames,
+            classname=classname or classnames,
             attrs=attrs,
         )
         self.url = url
@@ -80,7 +94,7 @@ class LinkMenuItem(MenuItem):
             and self.label == other.label
             and self.url == other.url
             and self.icon_name == other.icon_name
-            and self.classnames == other.classnames
+            and self.classname == other.classname
             and self.attrs == other.attrs
         )
 
@@ -93,15 +107,21 @@ class ActionMenuItem(MenuItem):
         label: str,
         action: str,
         icon_name: str = "",
+        classname: str = "",
         classnames: str = "",
         method: str = "POST",
         attrs: Mapping[str, Any] = None,
     ):
+        if classnames:
+            warn(
+                "The `classnames` kwarg for sidebar ActionMenuItem is deprecated - use `classname` instead.",
+                category=RemovedInWagtail60Warning,
+            )
         super().__init__(
             name,
             label,
             icon_name=icon_name,
-            classnames=classnames,
+            classname=classname or classnames,
             attrs=attrs,
         )
         self.action = action
@@ -121,7 +141,7 @@ class ActionMenuItem(MenuItem):
             and self.action == other.action
             and self.method == other.method
             and self.icon_name == other.icon_name
-            and self.classnames == other.classnames
+            and self.classname == other.classname
             and self.attrs == other.attrs
         )
 
@@ -134,15 +154,21 @@ class SubMenuItem(MenuItem):
         label: str,
         menu_items: List[MenuItem],
         icon_name: str = "",
+        classname: str = "",
         classnames: str = "",
         footer_text: str = "",
         attrs: Mapping[str, Any] = None,
     ):
+        if classnames:
+            warn(
+                "The `classnames` kwarg for sidebar SubMenuItem is deprecated - use `classname` instead.",
+                category=RemovedInWagtail60Warning,
+            )
         super().__init__(
             name,
             label,
             icon_name=icon_name,
-            classnames=classnames,
+            classname=classname or classnames,
             attrs=attrs,
         )
         self.menu_items = menu_items
@@ -161,7 +187,7 @@ class SubMenuItem(MenuItem):
             and self.label == other.label
             and self.menu_items == other.menu_items
             and self.icon_name == other.icon_name
-            and self.classnames == other.classnames
+            and self.classname == other.classname
             and self.footer_text == other.footer_text
             and self.attrs == other.attrs
         )
@@ -176,15 +202,21 @@ class PageExplorerMenuItem(LinkMenuItem):
         url: str,
         start_page_id: int,
         icon_name: str = "",
+        classname: str = "",
         classnames: str = "",
         attrs: Mapping[str, Any] = None,
     ):
+        if classnames:
+            warn(
+                "The `classnames` kwarg for sidebar PageExplorerMenuItem is deprecated - use `classname` instead.",
+                category=RemovedInWagtail60Warning,
+            )
         super().__init__(
             name,
             label,
             url,
             icon_name=icon_name,
-            classnames=classnames,
+            classname=classname or classnames,
             attrs=attrs,
         )
         self.start_page_id = start_page_id
@@ -202,7 +234,7 @@ class PageExplorerMenuItem(LinkMenuItem):
             and self.url == other.url
             and self.start_page_id == other.start_page_id
             and self.icon_name == other.icon_name
-            and self.classnames == other.classnames
+            and self.classname == other.classname
             and self.attrs == other.attrs
         )
 

wagtail/admin/wagtail_hooks.py

@@ -90,7 +90,7 @@ class ExplorerMenuItem(MenuItem):
                 self.url,
                 start_page.id,
                 icon_name=self.icon_name,
-                classnames=self.classnames,
+                classname=self.classname,
             )
         else:
             return super().render_component(request)
@@ -114,7 +114,7 @@ class SettingsMenuItem(SubmenuMenuItem):
             self.label,
             self.menu.render_component(request),
             icon_name=self.icon_name,
-            classnames=self.classnames,
+            classname=self.classname,
             footer_text="Wagtail v" + __version__,
         )
 

wagtail/contrib/modeladmin/menus.py

@@ -12,16 +12,16 @@ class ModelAdminMenuItem(MenuItem):
         url = model_admin.url_helper.index_url
         menu_icon = model_admin.get_menu_icon()
         if menu_icon[:3] == "fa-":
-            classnames = "icon icon-%s" % menu_icon
+            classname = "icon icon-%s" % menu_icon
             icon_name = None
         else:
-            classnames = ""
+            classname = ""
             icon_name = menu_icon
         super().__init__(
             label=model_admin.get_menu_label(),
             url=url,
             name=model_admin.get_menu_item_name(),
-            classnames=classnames,
+            classname=classname,
             icon_name=icon_name,
             order=order,
         )
@@ -40,16 +40,16 @@ class GroupMenuItem(SubmenuMenuItem):
     def __init__(self, modeladmingroup, order, menu):
         menu_icon = modeladmingroup.get_menu_icon()
         if menu_icon[:3] == "fa-":
-            classnames = "icon icon-%s" % menu_icon
+            classname = "icon icon-%s" % menu_icon
             icon_name = None
         else:
-            classnames = ""
+            classname = ""
             icon_name = menu_icon
         super().__init__(
             label=modeladmingroup.get_menu_label(),
             menu=menu,
             name=modeladmingroup.get_menu_item_name(),
-            classnames=classnames,
+            classname=classname,
             icon_name=icon_name,
             order=order,
         )

wagtail/contrib/settings/registry.py

@@ -1,3 +1,5 @@
+from warnings import warn
+
 from django.apps import apps
 from django.contrib.auth.models import Permission
 from django.urls import reverse
@@ -10,21 +12,27 @@ from wagtail.admin.admin_url_finder import (
 )
 from wagtail.admin.menu import MenuItem
 from wagtail.permission_policies import ModelPermissionPolicy
+from wagtail.utils.deprecation import RemovedInWagtail60Warning
 
 from .permissions import user_can_edit_setting_type
 
 
 class SettingMenuItem(MenuItem):
-    def __init__(self, model, icon="cog", classnames="", **kwargs):
-
+    def __init__(self, model, icon="cog", classname="", classnames="", **kwargs):
+        if classnames:
+            warn(
+                "The `classnames` kwarg for SettingMenuItem is deprecated - use `classname` instead.",
+                category=RemovedInWagtail60Warning,
+            )
+        classname = classname or classnames
         # Special-case FontAwesome icons to avoid the breaking changes for those customisations.
         if icon.startswith("fa-"):
             icon_name = ""
             icon_classes = "icon icon-" + icon
-            if classnames:
-                classnames += " " + icon_classes
+            if classname:
+                classname += " " + icon_classes
             else:
-                classnames = icon_classes
+                classname = icon_classes
         else:
             icon_name = icon
 
@@ -35,7 +43,7 @@ class SettingMenuItem(MenuItem):
                 "wagtailsettings:edit",
                 args=[model._meta.app_label, model._meta.model_name],
             ),
-            classnames=classnames,
+            classname=classname,
             icon_name=icon_name,
             **kwargs,
         )

wagtail/contrib/settings/tests/generic/test_admin.py

@@ -52,18 +52,18 @@ class TestGenericSettingMenu(WagtailTestUtils, TestCase):
 
     def test_menu_item_icon(self):
         menu_item = SettingMenuItem(
-            IconGenericSetting, icon="tag", classnames="test-class"
+            IconGenericSetting, icon="tag", classname="test-class"
         )
         self.assertEqual(menu_item.icon_name, "tag")
-        self.assertEqual(menu_item.classnames, "test-class")
+        self.assertEqual(menu_item.classname, "test-class")
 
     def test_menu_item_icon_fontawesome(self):
         menu_item = SettingMenuItem(
-            IconGenericSetting, icon="fa-suitcase", classnames="test-class"
+            IconGenericSetting, icon="fa-suitcase", classname="test-class"
         )
         self.assertEqual(menu_item.icon_name, "")
         self.assertEqual(
-            set(menu_item.classnames.split(" ")),
+            set(menu_item.classname.split(" ")),
             {"icon", "icon-fa-suitcase", "test-class"},
         )
 

wagtail/contrib/settings/tests/site_specific/test_admin.py

@@ -50,19 +50,17 @@ class TestSiteSettingMenu(WagtailTestUtils, TestCase):
         )
 
     def test_menu_item_icon(self):
-        menu_item = SettingMenuItem(
-            IconSiteSetting, icon="tag", classnames="test-class"
-        )
+        menu_item = SettingMenuItem(IconSiteSetting, icon="tag", classname="test-class")
         self.assertEqual(menu_item.icon_name, "tag")
-        self.assertEqual(menu_item.classnames, "test-class")
+        self.assertEqual(menu_item.classname, "test-class")
 
     def test_menu_item_icon_fontawesome(self):
         menu_item = SettingMenuItem(
-            IconSiteSetting, icon="fa-suitcase", classnames="test-class"
+            IconSiteSetting, icon="fa-suitcase", classname="test-class"
         )
         self.assertEqual(menu_item.icon_name, "")
         self.assertEqual(
-            set(menu_item.classnames.split(" ")),
+            set(menu_item.classname.split(" ")),
             {"icon", "icon-fa-suitcase", "test-class"},
         )
 

wagtail/test/testapp/wagtail_hooks.py

@@ -73,7 +73,7 @@ def register_kittens_menu_item():
     return KittensMenuItem(
         "Kittens!",
         "http://www.tomroyal.com/teaandkittens/",
-        classnames="kitten--test",
+        classname="kitten--test",
         name="kittens",
         icon_name="kitten",
         attrs={"data-is-custom": "true"},
@@ -95,7 +95,7 @@ def register_custom_search_area():
     return MyCustomSearchArea(
         "My Search",
         "/customsearch/",
-        classnames="search--custom-class",
+        classname="search--custom-class",
         icon_name="custom",
         attrs={"is-custom": "true"},
         order=10000,