Support nested elements

Author: lovelydinosaur

docs/navigation.md

@@ -52,4 +52,28 @@ nav = [
 ]
 ```
 
-This allows the theme to display navigation controls, as well as including `← previous` and `next →` links.
+This allows the theme to display navigation controls, as well as including `← previous` and `next →` links.
+
+The navigation configuration can also include nested elements.
+
+```
+[mkdocs]
+version = 2
+
+[site]
+title = "MkDocs"
+favicon = "📘"
+nav = [
+    {title="Introduction", path="index.md"},
+    {title="Tutorial", children=[
+        {title="Creating a project", path="tutorial/new.md"},
+        {title="Adding pages", path="tutorial/pages.md"},
+        {title="Publishing your work", path="tutorial/publish.md"},
+    ]},
+    {title="Topics", children=[
+        {title="Page layouts", path="topics/layouts.md"},
+        {title="Typography", path="topics/typography.md"},
+        {title="Color schemes", path="topics/schemes.md"},
+    ]}
+]
+```

src/mkdocs/mkdocs.py

@@ -289,11 +289,11 @@ def nav_lines(self, nav: dict, indent="") -> list[str]:
     def render(self, resource: Resource, resources: list[Resource], config: dict, env: jinja2.Environment, md: markdown.Markdown) -> bytes:
         if resource.path.suffix == '.md':
             mapping = {resource.path: resource.url for resource in resources}
-            with PageContext(resource.path, mapping) as page:
+            with PageContext(resource.path, mapping, relative=False) as page:
                 nav_lines = self.nav_lines(config['site']['nav'])
                 nav_text = '\n'.join(nav_lines)
                 nav_html = md.reset().convert(nav_text)
-            with PageContext(resource.path, mapping):
+            with PageContext(resource.path, mapping, relative=True):
                 page_text = resource.read().decode('utf-8')
                 page_html = md.reset().convert(page_text)
 

src/mkdocs/rewrite_urls.py

@@ -1,18 +1,23 @@
 import contextvars
 import markdown
-import posixpath
 import httpx
+import os
 import pathlib
+import posixpath
 
 
 page_context = contextvars.ContextVar('page_context')
 
 
+def joinpath(x: pathlib.Path, y: pathlib.Path):
+    return pathlib.Path(os.path.normpath(x.joinpath(y)))
+
 class PageContext:
-    def __init__(self, path: pathlib.Path, path_to_url: dict[pathlib.Path, str]):
+    def __init__(self, path: pathlib.Path, path_to_url: dict[pathlib.Path, str], relative: bool):
         self.path = path
         self.path_to_url = path_to_url
         self.url_to_path = {u: p for p, u in path_to_url.items()}
+        self.relative = relative
 
     def __enter__(self):
         self._token = page_context.set(self)
@@ -31,6 +36,7 @@ def run(self, root):
         link = ''
 
         for el in root.iter():
+            # We want to rewrite image and links.
             if el.tag == 'a':
                 key = 'href'
                 link = el.get(key)
@@ -43,11 +49,21 @@ def run(self, root):
 
             if link:
                 url = httpx.URL(link)
+                # We want to rewrite relative links... '/page'
+                # We don't want to rewrite external links. 'https://elsewhere.com/here'
+                # We don't want to rewrite anchor links. '#section'
                 if url.is_relative_url and url._uri_reference.path:
+                    link = pathlib.PosixPath(url.path)
+
+                    # Path to the current page...
                     from_path = ctx.path
-                    to_path = ctx.path.parent.joinpath(url.path)
+                    # Path to the linked page...
+                    to_path = joinpath(ctx.path.parent, link) if ctx.relative else link
+                    # Current URL...
                     from_url = ctx.path_to_url[from_path]
+                    # Linked URL...
                     to_url =  ctx.path_to_url.get(to_path)
+
                     if to_url is None:
                         continue
                     rewrite = posixpath.relpath(to_url, from_url)
@@ -60,10 +76,12 @@ def run(self, root):
                     el.set(key, rewrite)
                     links.append({"title": el.text, "url": rewrite})
 
+                    # Is this is a link to the current page?
                     if from_url == to_url:
                         el.set('class', 'active')
                         idx = len(links)
 
+        # We also want to track the previous and next link.
         links = [None] + links + [None]
         if idx is not None:
             ctx.previous = links[idx - 1]