Fix #3034: TOC highlighting on hosts with pretty URLs

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

@@ -14,6 +14,19 @@ class MDBookSidebarScrollbox extends HTMLElement {
         if (current_page.endsWith('/')) {
             current_page += 'index.html';
         }
+        // Normalize a URL for comparison by stripping .html suffix.
+        // This ensures TOC highlighting works on hosts that use "pretty URLs"
+        // (e.g. Cloudflare Pages) which strip the .html extension.
+        function normalizeUrl(url) {
+            if (url.endsWith('/index.html')) {
+                return url.slice(0, -'/index.html'.length + 1);
+            }
+            if (url.endsWith('.html')) {
+                return url.slice(0, -'.html'.length);
+            }
+            return url;
+        }
+        const normalizedCurrentPage = normalizeUrl(current_page);
         const links = Array.prototype.slice.call(this.querySelectorAll('a'));
         const l = links.length;
         for (let i = 0; i < l; ++i) {
@@ -24,6 +37,7 @@ class MDBookSidebarScrollbox extends HTMLElement {
             }
             // The 'index' page is supposed to alias the first chapter in the book.
             if (link.href === current_page
+                || normalizeUrl(link.href) === normalizedCurrentPage
                 || i === 0
                 && path_to_root === ''
                 && current_page.endsWith('/index.html')) {

tests/testsuite/toc.rs

@@ -141,6 +141,16 @@ fn check_link_target_fallback() {
     );
 }
 
+/// The generated toc.js should normalize URLs for comparison so that TOC
+/// highlighting works on hosts that use "pretty URLs" (stripping .html).
+/// See <https://github.com/rust-lang/mdBook/issues/3034>.
+#[test]
+fn toc_js_normalizes_urls_for_pretty_urls() {
+    BookTest::from_dir("toc/basic_toc")
+        .check_file_contains("book/toc*.js", "normalizeUrl")
+        .check_file_contains("book/toc*.js", "normalizeUrl(link.href) === normalizedCurrentPage");
+}
+
 // Checks formatting of summary names with inline elements.
 #[test]
 fn summary_with_markdown_formatting() {