From e24fd550e0a6e7e9c0cb513958696ff19d1183d0 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Marek=20Noco=C5=84?= <mnocon@users.noreply.github.com>
Date: Wed, 15 Oct 2025 14:52:39 +0200
Subject: [PATCH] Make error page version aware

---
 docs/css/page-not-found.css | 35 +++++------------------------------
 docs/js/error-page.js       | 20 ++++++++++++++++++++
 mkdocs.yml                  |  1 +
 theme/404.html              |  4 ++--
 4 files changed, 28 insertions(+), 32 deletions(-)
 create mode 100644 docs/js/error-page.js

diff --git a/docs/css/page-not-found.css b/docs/css/page-not-found.css
index 0af53f3e7b..ea65ff0d2a 100644
--- a/docs/css/page-not-found.css
+++ b/docs/css/page-not-found.css
@@ -1,38 +1,13 @@
 .page-not-found {
-    text-align: center;
-    margin: 50px;
+    display:flex;
+    flex-direction: column;
+    align-items: center;
+    margin: 50px;   
 }
 
 .page-not-found h1 {
     font-weight: normal;
+    text-align: center;
     font-size: 37px;
     margin: 30px 0 10px;
 }
-
-.page-not-found h2 {
-    font-weight: normal;
-    font-size: 30px;
-    margin: 0 0 70px;
-}
-
-.page-not-found h3 {
-    font-weight: normal;
-    font-size: 25px;
-    margin: 0 0 20px;
-    color: var(--dark-grey);
-}
-
-.page-not-found ul {
-    display: inline-flex;
-    list-style-type: none;
-    margin: 0;
-}
-
-.page-not-found ul li {
-    padding: 0 30px;
-    margin: 0;
-}
-
-.page-not-found li + li {
-    border-left: 1px solid black;
-}
\ No newline at end of file
diff --git a/docs/js/error-page.js b/docs/js/error-page.js
new file mode 100644
index 0000000000..d0524a30a2
--- /dev/null
+++ b/docs/js/error-page.js
@@ -0,0 +1,20 @@
+(function (global, doc) {
+    const errorPageContainer = doc.querySelector('.page-not-found');
+
+    if (!errorPageContainer) {
+        return;
+    }
+
+    // Replace all TOC links with the correct version
+    let currentVersion = '5.0';
+    const branchNameRegexp = /\/en\/([a-z0-9-_.]*)\//g.exec(document.location.href);
+
+    if (branchNameRegexp !== null && branchNameRegexp.hasOwnProperty(1) && branchNameRegexp[1].length) {
+        currentVersion = branchNameRegexp[1];
+    }
+
+    doc.querySelectorAll('.md-sidebar--primary .md-nav__item a, .page-not-found a').forEach(link => {
+        link.href = link.href.replace(/\/en\/([a-z0-9-_.]*)\//, `/en/${currentVersion}/`);
+    });
+
+})(window, window.document);
diff --git a/mkdocs.yml b/mkdocs.yml
index 68158e1d8b..47d5f55373 100644
--- a/mkdocs.yml
+++ b/mkdocs.yml
@@ -1001,6 +1001,7 @@ extra_javascript:
   - js/jquery.min.js
   - js/jquery-ui.min.js
   - js/custom.js
+  - js/error-page.js
   - js/release-notes.js
   - js/docs.switcher.js
   - '//cdn.jsdelivr.net/npm/docsearch.js@2/dist/cdn/docsearch.min.js'
diff --git a/theme/404.html b/theme/404.html
index c227eecc96..e688b286bb 100644
--- a/theme/404.html
+++ b/theme/404.html
@@ -2,8 +2,8 @@
 
 {% block content %}
 <div class="page-not-found">
-    <img src="/images/404.png" alt="Not found" />
     <h1>Page not found.</h1>
-    <a href="/">Back to front page</a>
+    <img src="/images/404.png" alt="Not found" />
+    <p>This link might be out-of-date. Go to the <a href="/">main documentation page</a> or <a href="{{ site_url }}/search_results">use the search</a> to find what you are looking for.</p>
 </div>
 {% endblock %}