rustdoc: use <details> tag for the source code sidebar

This fixes the extremely poor accessibility of the old system, making it
possible to navigate the sidebar by keyboard, and also implicitly gives the
sidebar items the correct ARIA roles.

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

@@ -1528,37 +1528,18 @@ kbd {
 	margin-bottom: 1em;
 }
 
-div.children {
-	padding-left: 27px;
-	display: none;
-}
-div.name {
+details.dir-entry > summary {
+	margin: 0 0 0 13px;
+	list-style-position: outside;
 	cursor: pointer;
-	position: relative;
-	margin-left: 16px;
 }
-div.files > a {
+
+details.dir-entry div.folders, details.dir-entry div.files {
+	padding-left: 27px;
+}
+
+details.dir-entry a {
 	display: block;
-	padding: 0 3px;
-}
-div.files > a:hover, div.name:hover {
-	background-color: #a14b4b;
-}
-div.name.expand + .children {
-	display: block;
-}
-div.name::before {
-	content: "\25B6";
-	padding-left: 4px;
-	font-size: 0.625rem;
-	position: absolute;
-	left: -16px;
-	top: 4px;
-}
-div.name.expand::before {
-	transform: rotate(90deg);
-	left: -15px;
-	top: 2px;
 }
 
 /* The hideme class is used on summary tags that contain a span with

src/librustdoc/html/static/css/themes/ayu.css

@@ -630,7 +630,8 @@ kbd {
 	color: #fff;
 	border-bottom-color: #5c6773;
 }
-#source-sidebar div.files > a:hover, div.name:hover {
+#source-sidebar div.files > a:hover, details.dir-entry summary:hover,
+#source-sidebar div.files > a:focus, details.dir-entry summary:focus {
 	background-color: #14191f;
 	color: #ffb44c;
 }

src/librustdoc/html/static/css/themes/dark.css

@@ -500,7 +500,8 @@ kbd {
 #source-sidebar > .title {
 	border-bottom-color: #ccc;
 }
-#source-sidebar div.files > a:hover, div.name:hover {
+#source-sidebar div.files > a:hover, details.dir-entry summary:hover,
+#source-sidebar div.files > a:focus, details.dir-entry summary:focus {
 	background-color: #444;
 }
 #source-sidebar div.files > .selected {

src/librustdoc/html/static/css/themes/light.css

@@ -484,7 +484,8 @@ kbd {
 #source-sidebar > .title {
 	border-bottom-color: #ccc;
 }
-#source-sidebar div.files > a:hover, div.name:hover {
+#source-sidebar div.files > a:hover, details.dir-entry summary:hover,
+#source-sidebar div.files > a:focus, details.dir-entry summary:focus {
 	background-color: #E0E0E0;
 }
 #source-sidebar div.files > .selected {

src/librustdoc/html/static/js/source-script.js

@@ -13,33 +13,27 @@ const rootPath = document.getElementById("rustdoc-vars").attributes["data-root-p
 let oldScrollPosition = 0;
 
 function createDirEntry(elem, parent, fullPath, hasFoundFile) {
-    const name = document.createElement("div");
-    name.className = "name";
+    const dirEntry = document.createElement("details");
+    const summary = document.createElement("summary");
+
+    dirEntry.className = "dir-entry";
 
     fullPath += elem["name"] + "/";
 
-    name.onclick = ev => {
-        if (hasClass(ev.target, "expand")) {
-            removeClass(ev.target, "expand");
-        } else {
-            addClass(ev.target, "expand");
-        }
-    };
-    name.innerText = elem["name"];
+    summary.innerText = elem["name"];
+    dirEntry.appendChild(summary);
 
-    const children = document.createElement("div");
-    children.className = "children";
     const folders = document.createElement("div");
     folders.className = "folders";
     if (elem.dirs) {
         for (const dir of elem.dirs) {
             if (createDirEntry(dir, folders, fullPath, hasFoundFile)) {
-                addClass(name, "expand");
+                dirEntry.open = true;
                 hasFoundFile = true;
             }
         }
     }
-    children.appendChild(folders);
+    dirEntry.appendChild(folders);
 
     const files = document.createElement("div");
     files.className = "files";
@@ -51,15 +45,14 @@ function createDirEntry(elem, parent, fullPath, hasFoundFile) {
             const w = window.location.href.split("#")[0];
             if (!hasFoundFile && w === file.href) {
                 file.className = "selected";
-                addClass(name, "expand");
+                dirEntry.open = true;
                 hasFoundFile = true;
             }
             files.appendChild(file);
         }
     }
-    children.appendChild(files);
-    parent.appendChild(name);
-    parent.appendChild(children);
+    dirEntry.appendChild(files);
+    parent.appendChild(dirEntry);
     return hasFoundFile;
 }
 

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

@@ -27,29 +27,29 @@ reload:
 // Waiting for the sidebar to be displayed...
 wait-for-css: ("#sidebar-toggle", {"visibility": "visible", "opacity": 1})
 assert-css: (
-    "#source-sidebar .expand + .children a.selected",
+    "#source-sidebar details[open] > .files a.selected",
     {"color": "rgb(0, 0, 0)", "background-color": "rgb(255, 255, 255)"},
 )
 // Without hover.
 assert-css: (
-    "#source-sidebar .expand + .children > .files a:not(.selected)",
+    "#source-sidebar details[open] > .files a:not(.selected)",
     {"color": "rgb(0, 0, 0)", "background-color": "rgba(0, 0, 0, 0)"},
 )
 // With hover.
-move-cursor-to: "#source-sidebar .expand + .children > .files a:not(.selected)"
+move-cursor-to: "#source-sidebar details[open] > .files a:not(.selected)"
 assert-css: (
-    "#source-sidebar .expand + .children > .files a:not(.selected)",
+    "#source-sidebar details[open] > .files a:not(.selected)",
     {"color": "rgb(0, 0, 0)", "background-color": "rgb(224, 224, 224)"},
 )
 // Without hover.
 assert-css: (
-    "#source-sidebar .expand + .children .folders .name",
+    "#source-sidebar details[open] > .folders > details > summary",
     {"color": "rgb(0, 0, 0)", "background-color": "rgba(0, 0, 0, 0)"},
 )
 // With hover.
-move-cursor-to: "#source-sidebar .expand + .children .folders .name"
+move-cursor-to: "#source-sidebar details[open] > .folders > details > summary"
 assert-css: (
-    "#source-sidebar .expand + .children .folders .name",
+    "#source-sidebar details[open] > .folders > details > summary",
     {"color": "rgb(0, 0, 0)", "background-color": "rgb(224, 224, 224)"},
 )
 
@@ -59,29 +59,29 @@ reload:
 // Waiting for the sidebar to be displayed...
 wait-for-css: ("#sidebar-toggle", {"visibility": "visible", "opacity": 1})
 assert-css: (
-    "#source-sidebar .expand + .children a.selected",
+    "#source-sidebar details[open] > .files > a.selected",
     {"color": "rgb(221, 221, 221)", "background-color": "rgb(51, 51, 51)"},
 )
 // Without hover.
 assert-css: (
-    "#source-sidebar .expand + .children > .files a:not(.selected)",
+    "#source-sidebar details[open] > .files > a:not(.selected)",
     {"color": "rgb(221, 221, 221)", "background-color": "rgba(0, 0, 0, 0)"},
 )
 // With hover.
-move-cursor-to: "#source-sidebar .expand + .children > .files a:not(.selected)"
+move-cursor-to: "#source-sidebar details[open] > .files a:not(.selected)"
 assert-css: (
-    "#source-sidebar .expand + .children > .files a:not(.selected)",
+    "#source-sidebar details[open] > .files a:not(.selected)",
     {"color": "rgb(221, 221, 221)", "background-color": "rgb(68, 68, 68)"},
 )
 // Without hover.
 assert-css: (
-    "#source-sidebar .expand + .children .folders .name",
+    "#source-sidebar details[open] > .folders > details > summary",
     {"color": "rgb(221, 221, 221)", "background-color": "rgba(0, 0, 0, 0)"},
 )
 // With hover.
-move-cursor-to: "#source-sidebar .expand + .children .folders .name"
+move-cursor-to: "#source-sidebar details[open] > .folders > details > summary"
 assert-css: (
-    "#source-sidebar .expand + .children .folders .name",
+    "#source-sidebar details[open] > .folders > details > summary",
     {"color": "rgb(221, 221, 221)", "background-color": "rgb(68, 68, 68)"},
 )
 
@@ -91,29 +91,29 @@ reload:
 // Waiting for the sidebar to be displayed...
 wait-for-css: ("#sidebar-toggle", {"visibility": "visible", "opacity": 1})
 assert-css: (
-    "#source-sidebar .expand + .children a.selected",
+    "#source-sidebar details[open] > .files a.selected",
     {"color": "rgb(255, 180, 76)", "background-color": "rgb(20, 25, 31)"},
 )
 // Without hover.
 assert-css: (
-    "#source-sidebar .expand + .children > .files a:not(.selected)",
+    "#source-sidebar details[open] > .files a:not(.selected)",
     {"color": "rgb(197, 197, 197)", "background-color": "rgba(0, 0, 0, 0)"},
 )
 // With hover.
-move-cursor-to: "#source-sidebar .expand + .children > .files a:not(.selected)"
+move-cursor-to: "#source-sidebar details[open] > .files a:not(.selected)"
 assert-css: (
-    "#source-sidebar .expand + .children > .files a:not(.selected)",
+    "#source-sidebar details[open] > .files a:not(.selected)",
     {"color": "rgb(255, 180, 76)", "background-color": "rgb(20, 25, 31)"},
 )
 // Without hover.
 assert-css: (
-    "#source-sidebar .expand + .children .folders .name",
+    "#source-sidebar details[open] > .folders > details > summary",
     {"color": "rgb(197, 197, 197)", "background-color": "rgba(0, 0, 0, 0)"},
 )
 // With hover.
-move-cursor-to: "#source-sidebar .expand + .children .folders .name"
+move-cursor-to: "#source-sidebar details[open] > .folders > details > summary"
 assert-css: (
-    "#source-sidebar .expand + .children .folders .name",
+    "#source-sidebar details[open] > .folders > details > summary",
     {"color": "rgb(255, 180, 76)", "background-color": "rgb(20, 25, 31)"},
 )
 

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

@@ -34,19 +34,13 @@ assert-document-property: ({"URL": "/lib.rs.html"}, ENDS_WITH)
 click: "#sidebar-toggle"
 assert: ".source-sidebar-expanded"
 
-// We check that the first entry of the sidebar is collapsed (which, for whatever reason,
-// is number 2 and not 1...).
-assert-attribute: ("#source-sidebar .name:nth-child(2)", {"class": "name"})
-assert-text: ("#source-sidebar .name:nth-child(2)", "implementors")
-// We also check its children are hidden too.
-assert-css: ("#source-sidebar .name:nth-child(2) + .children", {"display": "none"})
+// We check that the first entry of the sidebar is collapsed
+assert-property: ("#source-sidebar details:first-of-type", {"open": "false"})
+assert-text: ("#source-sidebar details:first-of-type > summary", "implementors")
 // We now click on it.
-click: "#source-sidebar .name:nth-child(2)"
-assert-attribute: ("#source-sidebar .name:nth-child(2)", {"class": "name expand"})
-// Checking that its children are displayed as well.
-assert-css: ("#source-sidebar .name:nth-child(2) + .children", {"display": "block"})
+click: "#source-sidebar details:first-of-type > summary"
+assert-property: ("#source-sidebar details:first-of-type", {"open": "true"})
 
 // And now we collapse it again.
-click: "#source-sidebar .name:nth-child(2)"
-assert-attribute: ("#source-sidebar .name:nth-child(2)", {"class": "name"})
-assert-css: ("#source-sidebar .name:nth-child(2) + .children", {"display": "none"})
+click: "#source-sidebar details:first-of-type > summary"
+assert-property: ("#source-sidebar details:first-of-type", {"open": "false"})