Define a base class for all navigation item classes

docs/dev-guide/themes.md

@@ -408,7 +408,7 @@ on the homepage:
         show_root_full_path: false
         heading_level: 5
 
-::: mkdocs.structure.pages.Page.parent
+::: mkdocs.structure.StructureItem.parent
     options:
         show_root_full_path: false
         heading_level: 5
@@ -479,7 +479,7 @@ The following attributes are available on `section` objects:
         show_root_full_path: false
         heading_level: 5
 
-::: mkdocs.structure.nav.Section.parent
+::: mkdocs.structure.StructureItem.parent
     options:
         show_root_full_path: false
         heading_level: 5
@@ -533,7 +533,7 @@ The following attributes are available on `link` objects:
         show_root_full_path: false
         heading_level: 5
 
-::: mkdocs.structure.nav.Link.parent
+::: mkdocs.structure.StructureItem.parent
     options:
         show_root_full_path: false
         heading_level: 5

mkdocs/structure/__init__.py

@@ -0,0 +1,36 @@
+from __future__ import annotations
+
+import abc
+from typing import TYPE_CHECKING, Iterable
+
+if TYPE_CHECKING:
+    from mkdocs.structure.nav import Section
+
+
+class StructureItem(metaclass=abc.ABCMeta):
+    """An item in MkDocs structure - see concrete subclasses Section, Page or Link."""
+
+    @abc.abstractmethod
+    def __init__(self):
+        ...
+
+    parent: Section | None = None
+    """The immediate parent of the item in the site navigation. `None` if it's at the top level."""
+
+    @property
+    def is_top_level(self) -> bool:
+        return self.parent is None
+
+    title: str | None
+    is_section: bool = False
+    is_page: bool = False
+    is_link: bool = False
+
+    @property
+    def ancestors(self) -> Iterable[StructureItem]:
+        if self.parent is None:
+            return []
+        return [self.parent, *self.parent.ancestors]
+
+    def _indent_print(self, depth=0):
+        return ('    ' * depth) + repr(self)

mkdocs/structure/nav.py

@@ -4,6 +4,7 @@
 from typing import TYPE_CHECKING, Iterator, TypeVar
 from urllib.parse import urlsplit
 
+from mkdocs.structure import StructureItem
 from mkdocs.structure.pages import Page
 from mkdocs.utils import nest_paths
 
@@ -16,7 +17,7 @@
 
 
 class Navigation:
-    def __init__(self, items: list[Page | Section | Link], pages: list[Page]) -> None:
+    def __init__(self, items: list, pages: list[Page]) -> None:
         self.items = items  # Nested List with full navigation of Sections, Pages, and Links.
         self.pages = pages  # Flat List of subset of Pages in nav, in order.
 
@@ -32,34 +33,30 @@ def __init__(self, items: list[Page | Section | Link], pages: list[Page]) -> Non
     pages: list[Page]
     """A flat list of all [page][mkdocs.structure.pages.Page] objects contained in the navigation."""
 
-    def __repr__(self):
+    def __str__(self) -> str:
         return '\n'.join(item._indent_print() for item in self)
 
-    def __iter__(self) -> Iterator[Page | Section | Link]:
+    def __iter__(self) -> Iterator:
         return iter(self.items)
 
     def __len__(self) -> int:
         return len(self.items)
 
 
-class Section:
-    def __init__(self, title: str, children: list[Page | Section | Link]) -> None:
+class Section(StructureItem):
+    def __init__(self, title: str, children: list[StructureItem]) -> None:
         self.title = title
         self.children = children
 
-        self.parent = None
         self.active = False
 
     def __repr__(self):
-        return f"Section(title='{self.title}')"
+        return f"Section(title={self.title!r})"
 
     title: str
     """The title of the section."""
 
-    parent: Section | None
-    """The immediate parent of the section or `None` if the section is at the top level."""
-
-    children: list[Page | Section | Link]
+    children: list[StructureItem]
     """An iterable of all child navigation objects. Children may include nested sections, pages and links."""
 
     @property
@@ -87,28 +84,21 @@ def active(self, value: bool):
     is_link: bool = False
     """Indicates that the navigation object is a "link" object. Always `False` for section objects."""
 
-    @property
-    def ancestors(self):
-        if self.parent is None:
-            return []
-        return [self.parent] + self.parent.ancestors
-
-    def _indent_print(self, depth=0):
-        ret = ['{}{}'.format('    ' * depth, repr(self))]
+    def _indent_print(self, depth: int = 0):
+        ret = [super()._indent_print(depth)]
         for item in self.children:
             ret.append(item._indent_print(depth + 1))
         return '\n'.join(ret)
 
 
-class Link:
+class Link(StructureItem):
     def __init__(self, title: str, url: str):
         self.title = title
         self.url = url
-        self.parent = None
 
     def __repr__(self):
-        title = f"'{self.title}'" if (self.title is not None) else '[blank]'
-        return f"Link(title={title}, url='{self.url}')"
+        title = f"{self.title!r}" if self.title is not None else '[blank]'
+        return f"Link(title={title}, url={self.url!r})"
 
     title: str
     """The title of the link. This would generally be used as the label of the link."""
@@ -117,9 +107,6 @@ def __repr__(self):
     """The URL that the link points to. The URL should always be an absolute URLs and
     should not need to have `base_url` prepended."""
 
-    parent: Section | None
-    """The immediate parent of the link. `None` if the link is at the top level."""
-
     children: None = None
     """Links do not contain children and the attribute is always `None`."""
 
@@ -135,15 +122,6 @@ def __repr__(self):
     is_link: bool = True
     """Indicates that the navigation object is a "link" object. Always `True` for link objects."""
 
-    @property
-    def ancestors(self):
-        if self.parent is None:
-            return []
-        return [self.parent] + self.parent.ancestors
-
-    def _indent_print(self, depth=0):
-        return '{}{}'.format('    ' * depth, repr(self))
-
 
 def get_navigation(files: Files, config: MkDocsConfig) -> Navigation:
     """Build site navigation from config and files."""

mkdocs/structure/pages.py

@@ -5,7 +5,7 @@
 import os
 import posixpath
 import warnings
-from typing import TYPE_CHECKING, Any, Callable, Mapping, MutableMapping
+from typing import TYPE_CHECKING, Any, Callable, MutableMapping
 from urllib.parse import unquote as urlunquote
 from urllib.parse import urljoin, urlsplit, urlunsplit
 
@@ -15,6 +15,7 @@
 import markdown.treeprocessors
 from markdown.util import AMP_SUBSTITUTE
 
+from mkdocs.structure import StructureItem
 from mkdocs.structure.toc import get_toc
 from mkdocs.utils import get_build_date, get_markdown_title, meta, weak_property
 
@@ -23,7 +24,6 @@
 
     from mkdocs.config.defaults import MkDocsConfig
     from mkdocs.structure.files import File, Files
-    from mkdocs.structure.nav import Section
     from mkdocs.structure.toc import TableOfContents
 
 _unescape: Callable[[str], str]
@@ -36,17 +36,14 @@
 log = logging.getLogger(__name__)
 
 
-class Page:
-    def __init__(
-        self, title: str | None, file: File, config: MkDocsConfig | Mapping[str, Any]
-    ) -> None:
+class Page(StructureItem):
+    def __init__(self, title: str | None, file: File, config: MkDocsConfig) -> None:
         file.page = self
         self.file = file
         if title is not None:
             self.title = title
 
         # Navigation attributes
-        self.parent = None
         self.children = None
         self.previous_page = None
         self.next_page = None
@@ -74,12 +71,9 @@ def __eq__(self, other) -> bool:
         )
 
     def __repr__(self):
-        title = f"'{self.title}'" if (self.title is not None) else '[blank]'
+        title = f"{self.title!r}" if self.title is not None else '[blank]'
         url = self.abs_url or self.file.url
-        return f"Page(title={title}, url='{url}')"
-
-    def _indent_print(self, depth=0):
-        return '{}{}'.format('    ' * depth, repr(self))
+        return f"Page(title={title}, url={url!r})"
 
     markdown: str | None
     """The original Markdown content from the file."""
@@ -133,10 +127,6 @@ def active(self, value: bool):
     def is_index(self) -> bool:
         return self.file.name == 'index'
 
-    @property
-    def is_top_level(self) -> bool:
-        return self.parent is None
-
     edit_url: str | None
     """The full URL to the source page in the source repository. Typically used to
     provide a link to edit the source page. [base_url][] should not be used with this
@@ -157,10 +147,6 @@ def is_homepage(self) -> bool:
     The value will be `None` if the current page is the last item in the site navigation
     or if the current page is not included in the navigation at all."""
 
-    parent: Section | None
-    """The immediate parent of the page in the site navigation. `None` if the
-    page is at the top level."""
-
     children: None = None
     """Pages do not contain children and the attribute is always `None`."""
 
@@ -173,12 +159,6 @@ def is_homepage(self) -> bool:
     is_link: bool = False
     """Indicates that the navigation object is a "link" object. Always `False` for page objects."""
 
-    @property
-    def ancestors(self):
-        if self.parent is None:
-            return []
-        return [self.parent] + self.parent.ancestors
-
     def _set_canonical_url(self, base: str | None) -> None:
         if base:
             if not base.endswith('/'):
@@ -242,7 +222,7 @@ def _set_title(self) -> None:
         )
 
     @weak_property
-    def title(self) -> str | None:
+    def title(self) -> str | None:  # type: ignore[override]
         """
         Returns the title for the current page.