rustdoc: dedup search form HTML

This change constructs the search form HTML using JavaScript, instead of plain HTML. It uses a custom element because

- the [parser]'s insert algorithm runs the connected callback synchronously, so we won't get layout jank
- it requires very little HTML, so it's a real win in size

[parser]: https://html.spec.whatwg.org/multipage/parsing.html#create-an-element-for-the-token

This shrinks the standard library by about 60MiB, by my test.

src/librustdoc/html/static/js/storage.js

@@ -239,3 +239,46 @@ window.addEventListener("pageshow", ev => {
         setTimeout(updateSidebarWidth, 0);
     }
 });
+
+// Custom elements are used to insert some JS-dependent features into Rustdoc,
+// because the [parser] runs the connected callback
+// synchronously. It needs to be added synchronously so that nothing below it
+// becomes visible until after it's done. Otherwise, you get layout jank.
+//
+// That's also why this is in storage.js and not main.js.
+//
+// [parser]: https://html.spec.whatwg.org/multipage/parsing.html
+class RustdocSearchElement extends HTMLElement {
+    constructor() {
+        super();
+    }
+    connectedCallback() {
+        const rootPath = getVar("root-path");
+        const currentCrate = getVar("current-crate");
+        this.innerHTML = `<nav class="sub">
+            <form class="search-form">
+                <span></span> <!-- This empty span is a hacky fix for Safari - See #93184 -->
+                <div id="sidebar-button" tabindex="-1">
+                    <a href="${rootPath}${currentCrate}/all.html" title="show sidebar"></a>
+                </div>
+                <input
+                    class="search-input"
+                    name="search"
+                    aria-label="Run search in the documentation"
+                    autocomplete="off"
+                    spellcheck="false"
+                    placeholder="Type ‘S’ or ‘/’ to search, ‘?’ for more options…"
+                    type="search">
+                <div id="help-button" tabindex="-1">
+                    <a href="${rootPath}help.html" title="help">?</a>
+                </div>
+                <div id="settings-menu" tabindex="-1">
+                    <a href="${rootPath}settings.html" title="settings">
+                        Settings
+                    </a>
+                </div>
+            </form>
+        </nav>`;
+    }
+}
+window.customElements.define("rustdoc-search", RustdocSearchElement);

src/librustdoc/html/templates/page.html

@@ -117,30 +117,9 @@
     <div class="sidebar-resizer"></div> {# #}
     <main> {# #}
         {% if page.css_class != "src" %}<div class="width-limiter">{% endif %}
-            <nav class="sub"> {# #}
-                <form class="search-form"> {# #}
-                    <span></span> {# This empty span is a hacky fix for Safari - See #93184 #}
-                    <div id="sidebar-button" tabindex="-1"> {# #}
-                        <a href="{{page.root_path|safe}}{{layout.krate|safe}}/all.html" title="show sidebar"></a> {# #}
-                    </div> {# #}
-                    <input {#+ #}
-                        class="search-input" {#+ #}
-                        name="search" {#+ #}
-                        aria-label="Run search in the documentation" {#+ #}
-                        autocomplete="off" {#+ #}
-                        spellcheck="false" {#+ #}
-                        placeholder="Type ‘S’ or ‘/’ to search, ‘?’ for more options…" {#+ #}
-                        type="search"> {# #}
-                    <div id="help-button" tabindex="-1"> {# #}
-                        <a href="{{page.root_path|safe}}help.html" title="help">?</a> {# #}
-                    </div> {# #}
-                    <div id="settings-menu" tabindex="-1"> {# #}
-                        <a href="{{page.root_path|safe}}settings.html" title="settings"> {# #}
-                            Settings {# #}
-                        </a> {# #}
-                    </div> {# #}
-                </form> {# #}
-            </nav> {# #}
+            {# defined in storage.js to avoid duplicating complex UI across every page #}
+            {# and because the search form only works if JS is enabled anyway #}
+            <rustdoc-search></rustdoc-search> {# #}
             <section id="main-content" class="content">{{ content|safe }}</section> {# #}
         {% if page.css_class != "src" %}</div>{% endif %}
     </main> {# #}

tests/rustdoc-gui/javascript-disabled.goml

@@ -4,7 +4,7 @@ javascript: false
 
 go-to: "file://" + |DOC_PATH| + "/test_docs/struct.Foo.html"
 show-text: true
-assert-css: (".sub", {"display": "none"})
+assert-false: ".sub"
 
 // Even though JS is disabled, we should still have themes applied. Links are never black-colored
 // if styles are applied so we check that they are not.

tests/rustdoc-gui/sidebar-source-code-display.goml

@@ -4,7 +4,7 @@ javascript: false
 go-to: "file://" + |DOC_PATH| + "/src/test_docs/lib.rs.html"
 // Since the javascript is disabled, there shouldn't be a toggle.
 wait-for-css: (".sidebar", {"display": "none"})
-assert-css: ("#sidebar-button", {"display": "none"})
+assert-false: "#sidebar-button"
 
 // Let's retry with javascript enabled.
 javascript: true