rustdoc: remove mobile topbar from source pages instead of hiding it

src/librustdoc/html/static/css/rustdoc.css

@@ -1807,10 +1807,6 @@ in storage.js plus the media query with (min-width: 701px)
 		top: 0;
 	}
 
-	.source .mobile-topbar {
-		display: none;
-	}
-
 	.sidebar-menu-toggle {
 		width: 45px;
 		/* Rare exception to specifying font sizes in rem. Since this is acting

src/librustdoc/html/static/js/main.js

@@ -735,14 +735,15 @@ function loadCss(cssFileName) {
     let oldSidebarScrollPosition = null;
 
     function showSidebar() {
-        if (window.innerWidth < window.RUSTDOC_MOBILE_BREAKPOINT) {
+        const mobile_topbar = document.querySelector(".mobile-topbar");
+        if (window.innerWidth < window.RUSTDOC_MOBILE_BREAKPOINT && mobile_topbar) {
             // This is to keep the scroll position on mobile.
             oldSidebarScrollPosition = window.scrollY;
             document.body.style.width = `${document.body.offsetWidth}px`;
             document.body.style.position = "fixed";
             document.body.style.top = `-${oldSidebarScrollPosition}px`;
-            document.querySelector(".mobile-topbar").style.top = `${oldSidebarScrollPosition}px`;
+            mobile_topbar.style.top = `${oldSidebarScrollPosition}px`;
-            document.querySelector(".mobile-topbar").style.position = "relative";
+            mobile_topbar.style.position = "relative";
         } else {
             oldSidebarScrollPosition = null;
         }
@@ -751,13 +752,14 @@ function loadCss(cssFileName) {
     }
 
     function hideSidebar() {
-        if (oldSidebarScrollPosition !== null) {
+        const mobile_topbar = document.querySelector(".mobile-topbar");
+        if (oldSidebarScrollPosition !== null && mobile_topbar) {
             // This is to keep the scroll position on mobile.
             document.body.style.width = "";
             document.body.style.position = "";
             document.body.style.top = "";
-            document.querySelector(".mobile-topbar").style.top = "";
+            mobile_topbar.style.top = "";
-            document.querySelector(".mobile-topbar").style.position = "";
+            mobile_topbar.style.position = "";
             // The scroll position is lost when resetting the style, hence why we store it in
             // `oldSidebarScrollPosition`.
             window.scrollTo(0, oldSidebarScrollPosition);

src/librustdoc/html/templates/page.html

@@ -73,6 +73,7 @@
     </div> {#- -#}
     <![endif]--> {#- -#}
     {{- layout.external_html.before_content|safe -}}
+    {%- if page.css_class != "source" -%}
     <nav class="mobile-topbar"> {#- -#}
         <button class="sidebar-menu-toggle">&#9776;</button> {#- -#}
         <a class="sidebar-logo" href="{{page.root_path|safe}}{{krate_with_trailing_slash|safe}}index.html"> {#- -#}
@@ -86,6 +87,7 @@
         </a> {#- -#}
         <h2 class="location"></h2> {#- -#}
     </nav> {#- -#}
+    {%- endif -%}
     <nav class="sidebar"> {#- -#}
         <a class="sidebar-logo" href="{{page.root_path|safe}}{{krate_with_trailing_slash|safe}}index.html"> {#- -#}
             <div class="logo-container"> {#- -#}

src/test/rustdoc-gui/sidebar-source-code.goml

@@ -42,4 +42,4 @@ assert-false: ".source-sidebar-expanded"
 assert: "nav.sidebar"
 
 // Check that the topbar is not visible
-assert-property: (".mobile-topbar", {"offsetParent": "null"})
+assert-false: ".mobile-topbar"