fix(docs): forward doc frontMatter.sidebar_custom_props to linking si…

…debar category (#7638)

packages/docusaurus-plugin-content-docs/src/props.ts

@@ -73,10 +73,28 @@ Available document ids are:
     }
   }
 
+  function getCategoryLinkCustomProps(
+    link: SidebarItemCategoryLink | undefined,
+  ) {
+    switch (link?.type) {
+      case 'doc':
+        return getDocById(link.id).frontMatter.sidebar_custom_props;
+      default:
+        return undefined;
+    }
+  }
+
   function convertCategory(item: SidebarItemCategory): PropSidebarItemCategory {
     const {link, ...rest} = item;
     const href = getCategoryLinkHref(link);
-    return {...rest, items: item.items.map(normalizeItem), ...(href && {href})};
+    const customProps = item.customProps ?? getCategoryLinkCustomProps(link);
+
+    return {
+      ...rest,
+      items: item.items.map(normalizeItem),
+      ...(href && {href}),
+      ...(customProps && {customProps}),
+    };
   }
 
   function normalizeItem(item: SidebarItem): PropSidebarItem {

website/docs/api/plugins/plugin-content-docs.md

@@ -273,6 +273,7 @@ Accepted fields:
 | `sidebar_label` | `string` | `title` | The text shown in the document sidebar for this document. |
 | `sidebar_position` | `number` | Default ordering | Controls the position of a doc inside the generated sidebar slice when using `autogenerated` sidebar items. See also [Autogenerated sidebar metadata](/docs/sidebar#autogenerated-sidebar-metadata). |
 | `sidebar_class_name` | `string` | `undefined` | Gives the corresponding sidebar label a special class name when using autogenerated sidebars. |
+| `sidebar_custom_props` | `string` | `undefined` | Assign custom metadata to the sidebar item referencing this doc. |
 | `hide_title` | `boolean` | `false` | Whether to hide the title at the top of the doc. It only hides a title declared through the front matter, and have no effect on a Markdown title at the top of your document. |
 | `hide_table_of_contents` | `boolean` | `false` | Whether to hide the table of contents to the right. |
 | `toc_min_heading_level` | `number` | `2` | The minimum heading level shown in the table of contents. Must be between 2 and 6 and lower or equal to the max value. |