From 718ceecfa2dc6ea97bcad25828f8b88e5cbda454 Mon Sep 17 00:00:00 2001
From: Eric Huss <eric@huss.org>
Date: Wed, 19 Nov 2025 17:06:49 -0800
Subject: [PATCH] Fix heading nav depth

This fixes an issue where when a heading goes from a larger to a smaller
level, it was going back too far so that subsequent headings would be at
a lower level than they should have been.

Fixes https://github.com/rust-lang/mdBook/issues/2944
---
 crates/mdbook-html/front-end/templates/toc.js.hbs | 2 +-
 tests/gui/heading-nav-collapsed.goml              | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/crates/mdbook-html/front-end/templates/toc.js.hbs b/crates/mdbook-html/front-end/templates/toc.js.hbs
index 81ec2c92..132da23c 100644
--- a/crates/mdbook-html/front-end/templates/toc.js.hbs
+++ b/crates/mdbook-html/front-end/templates/toc.js.hbs
@@ -392,7 +392,7 @@ window.customElements.define('mdbook-sidebar-scrollbox', MDBookSidebarScrollbox)
                     stack.push({level: nextLevel, ol: ol});
                 }
             } else if (level < currentLevel) {
-                while (stack.length > 1 && stack[stack.length - 1].level >= level) {
+                while (stack.length > 1 && stack[stack.length - 1].level > level) {
                     stack.pop();
                 }
             }
diff --git a/tests/gui/heading-nav-collapsed.goml b/tests/gui/heading-nav-collapsed.goml
index 8583b5fa..b64d1174 100644
--- a/tests/gui/heading-nav-collapsed.goml
+++ b/tests/gui/heading-nav-collapsed.goml
@@ -10,7 +10,7 @@ assert-text: (".current-header", "Heading 1")
 assert-attribute: ("li:has(> span > a[href='#heading-12'])", {"class": "header-item"})
 assert-attribute: ("li:has(> span > a[href='#heading-21'])", {"class": "header-item"})
 
-assert-property: ("div.on-this-page", {"innerHTML": '<ol class="section"><li class="header-item expanded"><span class="chapter-link-wrapper"><a href="#heading-1" class="header-in-summary current-header">Heading 1</a></span><ol class="section"><li class="header-item expanded"><span class="chapter-link-wrapper"><a href="#heading-11" class="header-in-summary">Heading 1.1</a></span></li><li class="header-item"><span class="chapter-link-wrapper"><a href="#heading-12" class="header-in-summary">Heading 1.2</a><a class="chapter-fold-toggle header-toggle"><div>❱</div></a></span><ol class="section"><li class="header-item expanded"><span class="chapter-link-wrapper"><a href="#heading-121" class="header-in-summary">Heading 1.2.1</a></span></li><li class="header-item expanded"><span class="chapter-link-wrapper"><a href="#heading-122" class="header-in-summary">Heading 1.2.2</a></span></li></ol></li></ol></li><li class="header-item expanded"><span class="chapter-link-wrapper"><a href="#heading-13" class="header-in-summary">Heading 1.3</a></span></li><li class="header-item expanded"><span class="chapter-link-wrapper"><a href="#heading-2" class="header-in-summary">Heading 2</a></span><ol class="section"><li class="header-item"><span class="chapter-link-wrapper"><a href="#heading-21" class="header-in-summary">Heading 2.1</a><a class="chapter-fold-toggle header-toggle"><div>❱</div></a></span><ol class="section"><li class="header-item"><span class="chapter-link-wrapper"><a href="#heading-211" class="header-in-summary">Heading 2.1.1</a><a class="chapter-fold-toggle header-toggle"><div>❱</div></a></span><ol class="section"><li class="header-item"><span class="chapter-link-wrapper"><a href="#heading-2111" class="header-in-summary">Heading 2.1.1.1</a><a class="chapter-fold-toggle header-toggle"><div>❱</div></a></span><ol class="section"><li class="header-item expanded"><span class="chapter-link-wrapper"><a href="#heading-21111" class="header-in-summary">Heading 2.1.1.1.1</a></span></li></ol></li></ol></li></ol></li></ol></li></ol>'})
+assert-property: ("div.on-this-page", {"innerHTML": '<ol class="section"><li class="header-item expanded"><span class="chapter-link-wrapper"><a href="#heading-1" class="header-in-summary current-header">Heading 1</a></span><ol class="section"><li class="header-item expanded"><span class="chapter-link-wrapper"><a href="#heading-11" class="header-in-summary">Heading 1.1</a></span></li><li class="header-item"><span class="chapter-link-wrapper"><a href="#heading-12" class="header-in-summary">Heading 1.2</a><a class="chapter-fold-toggle header-toggle"><div>❱</div></a></span><ol class="section"><li class="header-item expanded"><span class="chapter-link-wrapper"><a href="#heading-121" class="header-in-summary">Heading 1.2.1</a></span></li><li class="header-item expanded"><span class="chapter-link-wrapper"><a href="#heading-122" class="header-in-summary">Heading 1.2.2</a></span></li></ol></li><li class="header-item expanded"><span class="chapter-link-wrapper"><a href="#heading-13" class="header-in-summary">Heading 1.3</a></span></li></ol></li><li class="header-item expanded"><span class="chapter-link-wrapper"><a href="#heading-2" class="header-in-summary">Heading 2</a></span><ol class="section"><li class="header-item"><span class="chapter-link-wrapper"><a href="#heading-21" class="header-in-summary">Heading 2.1</a><a class="chapter-fold-toggle header-toggle"><div>❱</div></a></span><ol class="section"><li class="header-item"><span class="chapter-link-wrapper"><a href="#heading-211" class="header-in-summary">Heading 2.1.1</a><a class="chapter-fold-toggle header-toggle"><div>❱</div></a></span><ol class="section"><li class="header-item"><span class="chapter-link-wrapper"><a href="#heading-2111" class="header-in-summary">Heading 2.1.1.1</a><a class="chapter-fold-toggle header-toggle"><div>❱</div></a></span><ol class="section"><li class="header-item expanded"><span class="chapter-link-wrapper"><a href="#heading-21111" class="header-in-summary">Heading 2.1.1.1.1</a></span></li></ol></li></ol></li></ol></li></ol></li></ol>'})
 
 // Click 1.2, expands it.
 click: "a.header-in-summary[href='#heading-12']"