Fix empty sidebar entry for a heading that is a link

crates/mdbook-html/front-end/templates/toc.js.hbs

@@ -336,10 +336,17 @@ window.customElements.define('mdbook-sidebar-scrollbox', MDBookSidebarScrollbox)
         });
     }
 
-    // Takes the nodes from the given head and copies them over to the
-    // destination, along with some filtering.
+    // Takes the rendered content of the given heading and copies it over to
+    // the destination, along with some filtering.
     function filterHeader(source, dest) {
         const clone = source.cloneNode(true);
+        // Unwrap the injected permalink anchor (`<a class="header">`), keeping
+        // its children. When the heading itself is a link, the browser hoists
+        // that link out as a sibling of the (now empty) permalink anchor, so
+        // unwrapping here lets the actual heading text come through.
+        clone.querySelectorAll('a.header').forEach(headerLink => {
+            headerLink.replaceWith(...headerLink.childNodes);
+        });
         clone.querySelectorAll('mark').forEach(mark => {
             mark.replaceWith(...mark.childNodes);
         });
@@ -418,7 +425,7 @@ window.customElements.define('mdbook-sidebar-scrollbox', MDBookSidebarScrollbox)
             span.appendChild(a);
             a.href = '#' + header.id;
             a.classList.add('header-in-summary');
-            filterHeader(header.children[0], a);
+            filterHeader(header, a);
             a.addEventListener('click', headerThresholdClick);
             const nextHeader = headers[i + 1];
             if (nextHeader !== undefined) {

tests/gui/books/heading-nav/src/markup.md

@@ -10,6 +10,10 @@ Basic markup should be copied.
 
 Probably not super-wise to have headings with links, but at least they shouldn't explode.
 
+## [link-only](../index.html)
+
+A heading whose entire content is a link should still show its text in the sidebar.
+
 ## Heading with a custom id { #custom-id .custom-class }
 
 Make sure navigation works on a custom id.

tests/gui/heading-nav-markup.goml

@@ -3,11 +3,18 @@
 set-window-size: (1400, 800)
 go-to: |DOC_PATH| + "heading-nav/markup.html"
 
-assert-count: (".header-item", 4)
+assert-count: (".header-item", 5)
 assert-count: (".current-header", 1)
 assert-text: (".current-header", "Heading with code or italic or bold or strike")
 assert-property: (".current-header", {"innerHTML": "Heading with <code>code</code> or <em>italic</em> or <strong>bold</strong> or <del>strike</del>"})
 
+// A heading that contains a link should keep its text (and the link) in the sidebar.
+assert-text: ("a.header-in-summary[href='#heading-with-a-link']", "Heading with a link")
+assert-property: ("a.header-in-summary[href='#heading-with-a-link']", {"innerHTML": "Heading with a <a href=\"../index.html\">link</a>"})
+
+// A heading whose entire content is a link should still show its text.
+assert-text: ("a.header-in-summary[href='#link-only']", "link-only")
+
 // Clicking the custom one should work and should make it current.
 click: "a.header-in-summary[href='#custom-id']"
 assert-count: (".current-header", 1)