feat(v2): auto-generated sidebars, frontmatter-less sites (#4582)

* POC of autogenerated sidebars

* use combine-promises utility lib

* autogenerated sidebar poc working

* Revert "autogenerated sidebar poc working"

This reverts commit c81da980

* POC of auto-generated sidebars for community docs

* update tests

* add initial test suite for autogenerated sidebars + fix some edge cases

* Improve autogen sidebars: strip more number prefixes in folder breadcrumb + slugs

* fix typo!

* Add tests for partially generated sidebars + fix edge cases + extract sidebar generation code

* Ability to read category metadatas file from a file in the category

* fix tests

* change position of API

* ability to extract number prefix

* stable system to enable position frontmatter

* fix tests for autogen sidebar position

* renamings

* restore community sidebars

* rename frontmatter position -> sidebar_position

* make sidebarItemsGenerator fn configurable

* minor changes

* rename dirPath => dirName

* Make the init template use autogenerated sidebars

* fix options

* fix docusaurus site: remove test docs

* add _category_ file to docs pathsToWatch

* add _category_ file to docs pathsToWatch

* tutorial: use sidebar_position instead of file number prefixes

* Adapt Docusaurus tutorial for autogenerated sidebars

* remove slug: /

* polish the homepage template

* rename _category_ sidebar_position to just "position"

* test for custom sidebarItemsGenerator fn

* fix category metadata + add link to report tutorial issues

* fix absolute path breaking tests

* fix absolute path breaking tests

* Add test for floating number sidebar_position

* add sidebarItemsGenerator unit tests

* add processSidebars unit tests

* Fix init template broken links

* windows test

* increase code translations test timeout

* cleanup mockCategoryMetadataFiles after windows test fixed

* update init template positions

* fix windows tests

* fix comment

* Add autogenerated sidebar items documentation + rewrite the full sidebars page doc

* add useful comment

* fix code block title

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

@@ -70,9 +70,16 @@ module.exports = {
         include: ['**/*.md', '**/*.mdx'], // Extensions to include.
         /**
          * Path to sidebar configuration for showing a list of markdown pages.
-         * Warning: will change
          */
-        sidebarPath: '',
+        sidebarPath: 'sidebars.js',
+        /**
+         * Function used to replace the sidebar items of type "autogenerated"
+         * by real sidebar items (docs, categories, links...)
+         */
+        sidebarItemsGenerator: function ({item, version, docs}) {
+          // Use the provided data to create a custom "sidebar slice"
+          return [{type: 'doc', id: 'doc1'}];
+        },
         /**
          * Theme components used by the docs pages
          */
@@ -154,14 +161,16 @@ Markdown documents can use the following markdown frontmatter metadata fields, e
 
 - `id`: A unique document id. If this field is not present, the document's `id` will default to its file name (without the extension)
 - `title`: The title of your document. If this field is not present, the document's `title` will default to its `id`
-- `hide_title`: Whether to hide the title at the top of the doc. By default it is `false`
+- `hide_title`: Whether to hide the title at the top of the doc. By default, it is `false`
 - `hide_table_of_contents`: Whether to hide the table of contents to the right. By default it is `false`
 - `sidebar_label`: The text shown in the document sidebar and in the next/previous button for this document. If this field is not present, the document's `sidebar_label` will default to its `title`
+- `sidebar_position`: Permits to control the position of a doc inside the generated sidebar slice, when using `autogenerated` sidebar items. Can be Int or Float.
+- `strip_number_prefixes`: When a document has a number prefix (`001 - My Doc.md`, `2. MyDoc.md`...), it is automatically removed, and the prefix is used as `sidebar_position`. Use `strip_number_prefixes: false` if you want to disable this behavior
 - `custom_edit_url`: The URL for editing this document. If this field is not present, the document's edit URL will fall back to `editUrl` from options fields passed to `docusaurus-plugin-content-docs`
 - `keywords`: Keywords meta tag for the document page, for search engines
 - `description`: The description of your document, which will become the `<meta name="description" content="..."/>` and `<meta property="og:description" content="..."/>` in `<head>`, used by search engines. If this field is not present, it will default to the first line of the contents
 - `image`: Cover or thumbnail image that will be used when displaying the link to your post
-- `slug`: Allows to customize the document url
+- `slug`: Allows to customize the document url (`/<routeBasePath>/<slug>`). Support multiple patterns: `slug: my-doc`, `slug: /my/path/myDoc`, `slug: /`
 
 Example: