Improve click behavior of the source code mobile full-screen "sidebar"

On desktop, if you open the source code sidebar, it stays open even when you
move from page to page. It used to do the same thing on mobile, but I think
that's stupid. Since the file list fills the entire screen on mobile, and you
can't really do anything with the currently selected file other than dismiss
the "sidebar" to look at it, it's safe to assume that anybody who clicks a
file in that list probably wants the list to go away so they can see it.

4 files changed, 46 insertions, 2 deletions

diff --git a/src/librustdoc/html/static/css/rustdoc.css b/src/librustdoc/html/static/css/rustdoc.css
index 532b98d9bb9..04492da8226 100644
--- a/src/librustdoc/html/static/css/rustdoc.css
+++ b/src/librustdoc/html/static/css/rustdoc.css
@@ -1683,6 +1683,11 @@ details.rustdoc-toggle[open] > summary.hideme::after {
 
 /* Media Queries */
 
+/*
+WARNING: RUSTDOC_MOBILE_BREAKPOINT MEDIA QUERY;
+If you update this line, then you also need to update the line with the same warning
+in storage.js plus the media query with (max-width: 700px)
+*/
 @media (min-width: 701px) {
 	/* In case there is no documentation before a code block, we need to add some margin at the top
 	to prevent an overlay between the "collapse toggle" and the information tooltip.
@@ -1703,6 +1708,11 @@ details.rustdoc-toggle[open] > summary.hideme::after {
 	}
 }
 
+/*
+WARNING: RUSTDOC_MOBILE_BREAKPOINT MEDIA QUERY
+If you update this line, then you also need to update the line with the same warning
+in storage.js plus the media query with (min-width: 701px)
+*/
 @media (max-width: 700px) {
 	/* When linking to an item with an `id` (for instance, by clicking a link in the sidebar,
 	   or visiting a URL with a fragment like `#method.new`, we don't want the item to be obscured
diff --git a/src/librustdoc/html/static/js/source-script.js b/src/librustdoc/html/static/js/source-script.js
index acb1d8d7b5c..586c14c33a3 100644
--- a/src/librustdoc/html/static/js/source-script.js
+++ b/src/librustdoc/html/static/js/source-script.js
@@ -12,6 +12,12 @@
 const rootPath = document.getElementById("rustdoc-vars").attributes["data-root-path"].value;
 let oldScrollPosition = 0;
 
+function closeSidebarIfMobile() {
+    if (window.innerWidth < window.RUSTDOC_MOBILE_BREAKPOINT) {
+        updateLocalStorage("source-sidebar-show", "false");
+    }
+}
+
 function createDirEntry(elem, parent, fullPath, hasFoundFile) {
     const name = document.createElement("div");
     name.className = "name";
@@ -48,6 +54,7 @@ function createDirEntry(elem, parent, fullPath, hasFoundFile) {
             const file = document.createElement("a");
             file.innerText = file_text;
             file.href = rootPath + "src/" + fullPath + file_text + ".html";
+            file.addEventListener("click", closeSidebarIfMobile);
             const w = window.location.href.split("#")[0];
             if (!hasFoundFile && w === file.href) {
                 file.className = "selected";
@@ -66,7 +73,7 @@ function createDirEntry(elem, parent, fullPath, hasFoundFile) {
 function toggleSidebar() {
     const child = this.children[0];
     if (child.innerText === ">") {
-        if (window.innerWidth < 701) {
+        if (window.innerWidth < window.RUSTDOC_MOBILE_BREAKPOINT) {
             // This is to keep the scroll position on mobile.
             oldScrollPosition = window.scrollY;
             document.body.style.position = "fixed";
@@ -76,7 +83,7 @@ function toggleSidebar() {
         child.innerText = "<";
         updateLocalStorage("source-sidebar-show", "true");
     } else {
-        if (window.innerWidth < 701) {
+        if (window.innerWidth < window.RUSTDOC_MOBILE_BREAKPOINT) {
             // This is to keep the scroll position on mobile.
             document.body.style.position = "";
             document.body.style.top = "";
diff --git a/src/librustdoc/html/static/js/storage.js b/src/librustdoc/html/static/js/storage.js
index 1c4c8834488..0c5389d45e5 100644
--- a/src/librustdoc/html/static/js/storage.js
+++ b/src/librustdoc/html/static/js/storage.js
@@ -9,6 +9,11 @@ const darkThemes = ["dark", "ayu"];
 window.currentTheme = document.getElementById("themeStyle");
 window.mainTheme = document.getElementById("mainThemeStyle");
 
+// WARNING: RUSTDOC_MOBILE_BREAKPOINT MEDIA QUERY
+// If you update this line, then you also need to update the two media queries with the same
+// warning in rustdoc.css
+window.RUSTDOC_MOBILE_BREAKPOINT = 701;
+
 const settingsDataset = (function() {
     const settingsElement = document.getElementById("default-settings");
     if (settingsElement === null) {
diff --git a/src/test/rustdoc-gui/sidebar-source-code-display.goml b/src/test/rustdoc-gui/sidebar-source-code-display.goml
index c441f84a821..7728bfd025f 100644
--- a/src/test/rustdoc-gui/sidebar-source-code-display.goml
+++ b/src/test/rustdoc-gui/sidebar-source-code-display.goml
@@ -18,6 +18,16 @@ click: "#sidebar-toggle"
 // Because of the transition CSS, we check by using `wait-for-css` instead of `assert-css`.
 wait-for-css: ("#sidebar-toggle", {"visibility": "visible", "opacity": 1})
 
+// We now check that opening the sidebar and clicking a link will leave it open.
+// The behavior here on desktop is different than the behavior on mobile,
+// but since the sidebar doesn't fill the entire screen here, it makes sense to have the
+// sidebar stay resident.
+wait-for-css: (".sidebar", {"width": "300px"})
+assert-local-storage: {"rustdoc-source-sidebar-show": "true"}
+click: ".sidebar a.selected"
+goto: file://|DOC_PATH|/src/test_docs/lib.rs.html
+assert-local-storage: {"rustdoc-source-sidebar-show": "true"}
+
 // Now we check the display of the sidebar items.
 show-text: true
 
@@ -152,3 +162,15 @@ click: "#sidebar-toggle"
 wait-for-css: (".sidebar", {"width": "0px"})
 // The "scrollTop" property should be the same.
 assert-window-property: {"pageYOffset": "2519"}
+
+// We now check that opening the sidebar and clicking a link will close it.
+// The behavior here on mobile is different than the behavior on desktop,
+// but common sense dictates that if you have a list of files that fills the entire screen, and
+// you click one of them, you probably want to actually see the file's contents, and not just
+// make it the current selection.
+click: "#sidebar-toggle"
+wait-for-css: (".sidebar", {"width": "500px"})
+assert-local-storage: {"rustdoc-source-sidebar-show": "true"}
+click: ".sidebar a.selected"
+goto: file://|DOC_PATH|/src/test_docs/lib.rs.html
+assert-local-storage: {"rustdoc-source-sidebar-show": "false"}