Improve CSS for "hide contents, not items"

Introduce a first use of the `<details>` and `<summary>` tags as
replacements for the JS-built toggles. I think this has the potential to
replace all the JS toggles and generally clean up the JS, CSS, and HTML.

Split rendering of attributes into two cases: in the case where they are
rendered as descendents of a `<pre>` tag, where they use indent spaces and
newlines for formatting, matching their surrounding markup. In the case
where they are rendered as descendants of a `<code>` tag, they are
rendered as `<div>`. This let me clean up some fragile CSS that was
adjusting the margin-left of attributes depending on context.

Remove toggles for attributes. With the ALLOWED_ATTRIBUTES filter, it's
rare for an item to have more than one attribute, so hiding attributes
behind a toggle doesn't save any screen space in the common case.

Fix a couple of invocations of `matches!` that didn't compile on my
machine.

Fix a boolean for the JS `createToggle` call that was causing
"Expand description" to show up spuriously on already-expanded
descriptions.

Add JS for auto-hide settings and hide all / show all.

Remove a z-index property and some font color tweaks made unnecessary
by the <details> toggles.

Add CSS for the <details> toggles.

8 files changed, 116 insertions, 130 deletions

diff --git a/src/librustdoc/html/render/mod.rs b/src/librustdoc/html/render/mod.rs
index 00a19006bb9..d0d9034f6e6 100644
--- a/src/librustdoc/html/render/mod.rs
+++ b/src/librustdoc/html/render/mod.rs
@@ -43,7 +43,6 @@ use std::path::PathBuf;
 use std::str;
 use std::string::ToString;
 
-use itertools::Itertools;
 use rustc_ast_pretty::pprust;
 use rustc_attr::{Deprecation, StabilityLevel};
 use rustc_data_structures::fx::FxHashSet;
@@ -487,7 +486,6 @@ fn settings(root_path: &str, suffix: &str, themes: &[StylePath]) -> Result<Strin
         )
             .into(),
         ("auto-hide-large-items", "Auto-hide item contents for large items.", true).into(),
-        ("auto-hide-attributes", "Auto-hide item attributes.", true).into(),
         ("auto-hide-method-docs", "Auto-hide item methods' documentation", false).into(),
         ("auto-hide-trait-implementations", "Auto-hide trait implementation documentation", true)
             .into(),
@@ -936,19 +934,21 @@ fn render_assoc_item(
             + name.as_str().len()
             + generics_len;
 
-        let (indent, end_newline) = if parent == ItemType::Trait {
+        let (indent, indent_str, end_newline) = if parent == ItemType::Trait {
             header_len += 4;
-            (4, false)
+            let indent_str = "    ";
+            render_attributes_in_pre(w, meth, indent_str);
+            (4, indent_str, false)
         } else {
-            (0, true)
+            render_attributes_in_code(w, meth);
+            (0, "", true)
         };
-        render_attributes(w, meth, false);
         w.reserve(header_len + "<a href=\"\" class=\"fnname\">{".len() + "</a>".len());
         write!(
             w,
             "{}{}{}{}{}{}{}fn <a href=\"{href}\" class=\"fnname\">{name}</a>\
              {generics}{decl}{notable_traits}{where_clause}",
-            if parent == ItemType::Trait { "    " } else { "" },
+            indent_str,
             vis,
             constness,
             asyncness,
@@ -1004,35 +1004,33 @@ const ALLOWED_ATTRIBUTES: &[Symbol] = &[
     sym::non_exhaustive,
 ];
 
-// The `top` parameter is used when generating the item declaration to ensure it doesn't have a
-// left padding. For example:
-//
-// #[foo] <----- "top" attribute
-// struct Foo {
-//     #[bar] <---- not "top" attribute
-//     bar: usize,
-// }
-fn render_attributes(w: &mut Buffer, it: &clean::Item, top: bool) {
-    let attrs = it
-        .attrs
+fn attributes(it: &clean::Item) -> Vec<String> {
+    it.attrs
         .other_attrs
         .iter()
         .filter_map(|attr| {
             if ALLOWED_ATTRIBUTES.contains(&attr.name_or_empty()) {
-                Some(pprust::attribute_to_string(&attr))
+                Some(pprust::attribute_to_string(&attr).replace("\n", "").replace("  ", " "))
             } else {
                 None
             }
         })
-        .join("\n");
+        .collect()
+}
 
-    if !attrs.is_empty() {
-        write!(
-            w,
-            "<span class=\"docblock attributes{}\">{}</span>",
-            if top { " top-attr" } else { "" },
-            &attrs
-        );
+// When an attribute is rendered inside a `<pre>` tag, it is formatted using
+// a whitespace prefix and newline.
+fn render_attributes_in_pre(w: &mut Buffer, it: &clean::Item, prefix: &str) {
+    for a in attributes(it) {
+        write!(w, "{}{}\n", prefix, a);
+    }
+}
+
+// When an attribute is rendered inside a <code> tag, it is formatted using
+// a div to produce a newline after it.
+fn render_attributes_in_code(w: &mut Buffer, it: &clean::Item) {
+    for a in attributes(it) {
+        write!(w, "<div>{}</div>", a);
     }
 }
 
diff --git a/src/librustdoc/html/render/print_item.rs b/src/librustdoc/html/render/print_item.rs
index d5a5ecd3e88..03c4bb837f5 100644
--- a/src/librustdoc/html/render/print_item.rs
+++ b/src/librustdoc/html/render/print_item.rs
@@ -11,8 +11,8 @@ use rustc_span::symbol::{kw, sym, Symbol};
 
 use super::{
     collect_paths_for_type, document, ensure_trailing_slash, item_ty_to_strs, notable_traits_decl,
-    render_assoc_item, render_assoc_items, render_attributes, render_impl,
-    render_stability_since_raw, write_srclink, AssocItemLink, Context,
+    render_assoc_item, render_assoc_items, render_attributes_in_code, render_attributes_in_pre,
+    render_impl, render_stability_since_raw, write_srclink, AssocItemLink, Context,
 };
 use crate::clean::{self, GetDefId};
 use crate::formats::cache::Cache;
@@ -138,11 +138,15 @@ fn should_hide_fields(n_fields: usize) -> bool {
 }
 
 fn toggle_open(w: &mut Buffer, text: &str) {
-    write!(w, "<div class=\"docblock type-contents-toggle\" data-toggle-text=\"{}\">", text);
+    write!(
+        w,
+        "<details class=\"type-contents-toggle\"><summary class=\"hideme\"><span>Show {}</span></summary>",
+        text
+    );
 }
 
 fn toggle_close(w: &mut Buffer) {
-    w.write_str("</div>");
+    w.write_str("</details>");
 }
 
 fn item_module(w: &mut Buffer, cx: &Context<'_>, item: &clean::Item, items: &[clean::Item]) {
@@ -391,7 +395,7 @@ fn item_function(w: &mut Buffer, cx: &Context<'_>, it: &clean::Item, f: &clean::
     )
     .len();
     w.write_str("<pre class=\"rust fn\">");
-    render_attributes(w, it, false);
+    render_attributes_in_pre(w, it, "");
     write!(
         w,
         "{vis}{constness}{asyncness}{unsafety}{abi}fn \
@@ -420,7 +424,7 @@ fn item_trait(w: &mut Buffer, cx: &Context<'_>, it: &clean::Item, t: &clean::Tra
     // Output the trait definition
     wrap_into_docblock(w, |w| {
         w.write_str("<pre class=\"rust trait\">");
-        render_attributes(w, it, true);
+        render_attributes_in_pre(w, it, "");
         write!(
             w,
             "{}{}{}trait {}{}{}",
@@ -729,7 +733,7 @@ fn item_trait(w: &mut Buffer, cx: &Context<'_>, it: &clean::Item, t: &clean::Tra
 
 fn item_trait_alias(w: &mut Buffer, cx: &Context<'_>, it: &clean::Item, t: &clean::TraitAlias) {
     w.write_str("<pre class=\"rust trait-alias\">");
-    render_attributes(w, it, false);
+    render_attributes_in_pre(w, it, "");
     write!(
         w,
         "trait {}{}{} = {};</pre>",
@@ -750,7 +754,7 @@ fn item_trait_alias(w: &mut Buffer, cx: &Context<'_>, it: &clean::Item, t: &clea
 
 fn item_opaque_ty(w: &mut Buffer, cx: &Context<'_>, it: &clean::Item, t: &clean::OpaqueTy) {
     w.write_str("<pre class=\"rust opaque\">");
-    render_attributes(w, it, false);
+    render_attributes_in_pre(w, it, "");
     write!(
         w,
         "type {}{}{where_clause} = impl {bounds};</pre>",
@@ -771,7 +775,7 @@ fn item_opaque_ty(w: &mut Buffer, cx: &Context<'_>, it: &clean::Item, t: &clean:
 
 fn item_typedef(w: &mut Buffer, cx: &Context<'_>, it: &clean::Item, t: &clean::Typedef) {
     w.write_str("<pre class=\"rust typedef\">");
-    render_attributes(w, it, false);
+    render_attributes_in_pre(w, it, "");
     write!(
         w,
         "type {}{}{where_clause} = {type_};</pre>",
@@ -793,7 +797,7 @@ fn item_typedef(w: &mut Buffer, cx: &Context<'_>, it: &clean::Item, t: &clean::T
 fn item_union(w: &mut Buffer, cx: &Context<'_>, it: &clean::Item, s: &clean::Union) {
     wrap_into_docblock(w, |w| {
         w.write_str("<pre class=\"rust union\">");
-        render_attributes(w, it, true);
+        render_attributes_in_pre(w, it, "");
         render_union(w, it, Some(&s.generics), &s.fields, "", true, cx);
         w.write_str("</pre>")
     });
@@ -839,7 +843,7 @@ fn item_union(w: &mut Buffer, cx: &Context<'_>, it: &clean::Item, s: &clean::Uni
 fn item_enum(w: &mut Buffer, cx: &Context<'_>, it: &clean::Item, e: &clean::Enum) {
     wrap_into_docblock(w, |w| {
         w.write_str("<pre class=\"rust enum\">");
-        render_attributes(w, it, true);
+        render_attributes_in_pre(w, it, "");
         write!(
             w,
             "{}enum {}{}{}",
@@ -1019,7 +1023,7 @@ fn item_primitive(w: &mut Buffer, cx: &Context<'_>, it: &clean::Item) {
 
 fn item_constant(w: &mut Buffer, cx: &Context<'_>, it: &clean::Item, c: &clean::Constant) {
     w.write_str("<pre class=\"rust const\">");
-    render_attributes(w, it, false);
+    render_attributes_in_code(w, it);
 
     write!(
         w,
@@ -1058,7 +1062,7 @@ fn item_constant(w: &mut Buffer, cx: &Context<'_>, it: &clean::Item, c: &clean::
 fn item_struct(w: &mut Buffer, cx: &Context<'_>, it: &clean::Item, s: &clean::Struct) {
     wrap_into_docblock(w, |w| {
         w.write_str("<pre class=\"rust struct\">");
-        render_attributes(w, it, true);
+        render_attributes_in_code(w, it);
         render_struct(w, it, Some(&s.generics), s.struct_type, &s.fields, "", true, cx);
         w.write_str("</pre>")
     });
@@ -1107,7 +1111,7 @@ fn item_struct(w: &mut Buffer, cx: &Context<'_>, it: &clean::Item, s: &clean::St
 
 fn item_static(w: &mut Buffer, cx: &Context<'_>, it: &clean::Item, s: &clean::Static) {
     w.write_str("<pre class=\"rust static\">");
-    render_attributes(w, it, false);
+    render_attributes_in_code(w, it);
     write!(
         w,
         "{vis}static {mutability}{name}: {typ}</pre>",
@@ -1121,7 +1125,7 @@ fn item_static(w: &mut Buffer, cx: &Context<'_>, it: &clean::Item, s: &clean::St
 
 fn item_foreign_type(w: &mut Buffer, cx: &Context<'_>, it: &clean::Item) {
     w.write_str("<pre class=\"rust foreigntype\">extern {\n");
-    render_attributes(w, it, false);
+    render_attributes_in_code(w, it);
     write!(
         w,
         "    {}type {};\n}}</pre>",
@@ -1304,10 +1308,8 @@ fn render_union(
     }
 
     write!(w, " {{\n{}", tab);
-    let count_fields = fields
-        .iter()
-        .filter(|f| matches!(clean::StructFieldItem(..), *f.kind))
-        .count();
+    let count_fields =
+        fields.iter().filter(|f| matches!(*f.kind, clean::StructFieldItem(..))).count();
     let toggle = should_hide_fields(count_fields);
     if toggle {
         toggle_open(w, "fields");
@@ -1361,10 +1363,8 @@ fn render_struct(
                 write!(w, "{}", print_where_clause(g, cx.cache(), cx.tcx(), 0, true),)
             }
             w.write_str(" {");
-            let count_fields = fields
-                .iter()
-                .filter(|f| matches!(clean::StructFieldItem(..) = *f.kind))
-                .count();
+            let count_fields =
+                fields.iter().filter(|f| matches!(*f.kind, clean::StructFieldItem(..))).count();
             let has_visible_fields = count_fields > 0;
             let toggle = should_hide_fields(count_fields);
             if toggle {
diff --git a/src/librustdoc/html/static/main.js b/src/librustdoc/html/static/main.js
index af66a7a135a..1b14f67fce1 100644
--- a/src/librustdoc/html/static/main.js
+++ b/src/librustdoc/html/static/main.js
@@ -1,4 +1,3 @@
-// ignore-tidy-filelength
 // Local js definitions:
 /* global addClass, getSettingValue, hasClass */
 /* global onEach, onEachLazy, hasOwnProperty, removeClass, updateLocalStorage */
@@ -2316,6 +2315,9 @@ function hideThemeButtonState() {
         if (hasClass(innerToggle, "will-expand")) {
             updateLocalStorage("rustdoc-collapse", "false");
             removeClass(innerToggle, "will-expand");
+            onEachLazy(document.getElementsByTagName("details"), function(e) {
+                e.open = true;
+            });
             onEveryMatchingChild(innerToggle, "inner", function(e) {
                 e.innerHTML = labelForToggleButton(false);
             });
@@ -2328,6 +2330,9 @@ function hideThemeButtonState() {
         } else {
             updateLocalStorage("rustdoc-collapse", "true");
             addClass(innerToggle, "will-expand");
+            onEachLazy(document.getElementsByTagName("details"), function(e) {
+                e.open = false;
+            });
             onEveryMatchingChild(innerToggle, "inner", function(e) {
                 var parent = e.parentNode;
                 var superParent = null;
@@ -2569,6 +2574,7 @@ function hideThemeButtonState() {
         var toggle = createSimpleToggle(false);
         var hideMethodDocs = getSettingValue("auto-hide-method-docs") === "true";
         var hideImplementors = getSettingValue("auto-collapse-implementors") !== "false";
+        let hideLargeItemContents = getSettingValue("auto-hide-large-items") !== "false";
 
         var func = function(e) {
             var next = e.nextElementSibling;
@@ -2615,6 +2621,14 @@ function hideThemeButtonState() {
         onEachLazy(document.getElementsByClassName("associatedconstant"), func);
         onEachLazy(document.getElementsByClassName("impl"), funcImpl);
         var impl_call = function() {};
+        // Large items are hidden by default in the HTML. If the setting overrides that, show 'em.
+        if (!hideLargeItemContents) {
+            onEachLazy(document.getElementsByTagName("details"), function (e) {
+                if (hasClass(e, "type-contents-toggle")) {
+                    e.open = true;
+                }
+            });
+        }
         if (hideMethodDocs === true) {
             impl_call = function(e, newToggle) {
                 if (e.id.match(/^impl(?:-\d+)?$/) === null) {
@@ -2703,14 +2717,6 @@ function hideThemeButtonState() {
                         }
                     });
                 }
-            } else if (hasClass(e, "type-contents-toggle")) {
-                let text = e.getAttribute("data-toggle-text");
-                let hideItemContents = getSettingValue("auto-hide-large-items") !== "false";
-                let tog = createToggle(toggle, `Show ${text}`, null, "", !hideItemContents);
-                e.parentNode.insertBefore(tog,  e);
-                if (hideItemContents) {
-                    collapseDocs(e.previousSibling.childNodes[0], "toggle");
-                }
             }
             if (e.parentNode.id === "main") {
                 var otherMessage = "";
@@ -2744,7 +2750,7 @@ function hideThemeButtonState() {
                         otherMessage,
                         fontSize,
                         extraClass,
-                        false),
+                        true),
                     e);
                 if (hasClass(e, "non-exhaustive") === true) {
                     collapseDocs(e.previousSibling.childNodes[0], "toggle");
@@ -2763,38 +2769,6 @@ function hideThemeButtonState() {
         }
     }());
 
-    function createToggleWrapper(tog) {
-        var span = document.createElement("span");
-        span.className = "toggle-label";
-        span.style.display = "none";
-        span.innerHTML = "&nbsp;Expand&nbsp;attributes";
-        tog.appendChild(span);
-
-        var wrapper = document.createElement("div");
-        wrapper.className = "toggle-wrapper toggle-attributes";
-        wrapper.appendChild(tog);
-        return wrapper;
-    }
-
-    (function() {
-        // To avoid checking on "rustdoc-item-attributes" value on every loop...
-        var itemAttributesFunc = function() {};
-        if (getSettingValue("auto-hide-attributes") !== "false") {
-            itemAttributesFunc = function(x) {
-                collapseDocs(x.previousSibling.childNodes[0], "toggle");
-            };
-        }
-        var attributesToggle = createToggleWrapper(createSimpleToggle(false));
-        onEachLazy(main.getElementsByClassName("attributes"), function(i_e) {
-            var attr_tog = attributesToggle.cloneNode(true);
-            if (hasClass(i_e, "top-attr") === true) {
-                addClass(attr_tog, "top-attr");
-            }
-            i_e.parentNode.insertBefore(attr_tog, i_e);
-            itemAttributesFunc(i_e);
-        });
-    }());
-
     (function() {
         // To avoid checking on "rustdoc-line-numbers" value on every loop...
         var lineNumbersFunc = function() {};
diff --git a/src/librustdoc/html/static/rustdoc.css b/src/librustdoc/html/static/rustdoc.css
index 309e55670b1..64972bc2389 100644
--- a/src/librustdoc/html/static/rustdoc.css
+++ b/src/librustdoc/html/static/rustdoc.css
@@ -970,10 +970,6 @@ a.test-arrow:hover{
 	position: absolute;
 	left: -23px;
 	top: 0;
-
-	/* The click event for this is defined on the document,
-	   so bubbling does not work. See https://github.com/rust-lang/rust/issues/83332 */
-	z-index: 10;
 }
 
 h3 > .collapse-toggle, h4 > .collapse-toggle {
@@ -1058,11 +1054,6 @@ h3 > .collapse-toggle, h4 > .collapse-toggle {
 	margin-top: 3px;
 }
 
-/* for hiding fields/variants/associated items */
-.enum > .toggle-wrapper + .docblock, .struct > .toggle-wrapper + .docblock, .union > .toggle-wrapper + .docblock, .trait > .toggle-wrapper + .docblock {
-	margin-left: 0px;
-}
-
 .docblock > .section-header:first-child {
 	margin-left: 15px;
 	margin-top: 0;
@@ -1076,22 +1067,6 @@ h3 > .collapse-toggle, h4 > .collapse-toggle {
 	display: block;
 }
 
-.attributes {
-	display: block;
-	margin-top: 0px !important;
-	margin-right: 0px;
-	margin-bottom: 0px !important;
-	margin-left: 30px;
-}
-.toggle-attributes.collapsed {
-	margin-bottom: 0;
-}
-.impl-items > .toggle-attributes {
-	margin-left: 20px;
-}
-.impl-items .attributes {
-	font-weight: 500;
-}
 
 :target > code {
 	opacity: 1;
@@ -1778,16 +1753,56 @@ div.name.expand::before {
 	top: 2px;
 }
 
-/* This part is to fix the "Expand attributes" part in the type declaration. */
-.type-decl > pre > .toggle-wrapper.toggle-attributes.top-attr {
-	margin-left: 0 !important;
+/* The hideme class is used on summary tags that contain a span with
+	placeholder text shown only when the toggle is closed. For instance,
+	"Expand description" or "Show methods". */
+details > summary.hideme {
+	cursor: pointer;
+}
+
+details > summary::-webkit-details-marker {
+	display: none;
+}
+
+details > summary.hideme > span {
+	margin-left: 9px;
+	color: #999;
 }
-.type-decl > pre > .docblock.attributes.top-attr {
-	margin-left: 1.8em !important;
+
+details > summary::before {
+	content: "[+]";
+	font-weight: 300;
+	font-size: 0.8em;
+	color: #999;
+	letter-spacing: 1px;
+}
+
+details > summary.hideme::before {
+	position: relative;
 }
-.type-decl > pre .toggle-attributes {
-	margin-left: 2.2em;
+
+details > summary:not(.hideme)::before {
+	float: left;
 }
-.type-decl > pre > .docblock.attributes {
-	margin-left: 4em;
+
+/* When a "hideme" summary is open and the "Expand description" or "Show
+	methods" text is hidden, we want the [-] toggle that remains to not
+	affect the layout of the items to its right. To do that, we use
+	absolute positioning. Note that we also set position: relative
+	on the parent <details> to make this work properly. */
+details[open] > summary.hideme {
+	position: absolute;
+}
+
+details[open] {
+	position: relative;
+}
+
+details[open] > summary.hideme > span {
+	display: none;
+}
+
+details[open] > summary::before {
+	content: "[−]";
+	display: inline;
 }
diff --git a/src/librustdoc/html/static/storage.js b/src/librustdoc/html/static/storage.js
index c68128516d2..2ed87fdedae 100644
--- a/src/librustdoc/html/static/storage.js
+++ b/src/librustdoc/html/static/storage.js
@@ -1,6 +1,5 @@
 // From rust:
 /* global resourcesSuffix */
-
 var darkThemes = ["dark", "ayu"];
 window.currentTheme = document.getElementById("themeStyle");
 window.mainTheme = document.getElementById("mainThemeStyle");
diff --git a/src/librustdoc/html/static/themes/ayu.css b/src/librustdoc/html/static/themes/ayu.css
index 0404fa50b99..b24f4035ca8 100644
--- a/src/librustdoc/html/static/themes/ayu.css
+++ b/src/librustdoc/html/static/themes/ayu.css
@@ -218,7 +218,7 @@ a {
 	color: #c5c5c5;
 }
 
-.docblock:not(.type-decl) a:not(.srclink):not(.test-arrow):not(.collapse-toggle),
+.docblock:not(.type-decl) a:not(.srclink):not(.test-arrow),
 .docblock-short a:not(.srclink):not(.test-arrow), .item-info a,
 #help a {
 	color: #39AFD7;
diff --git a/src/librustdoc/html/static/themes/dark.css b/src/librustdoc/html/static/themes/dark.css
index 15b485a966f..e863ed03f51 100644
--- a/src/librustdoc/html/static/themes/dark.css
+++ b/src/librustdoc/html/static/themes/dark.css
@@ -176,7 +176,7 @@ a {
 	color: #ddd;
 }
 
-.docblock:not(.type-decl) a:not(.srclink):not(.test-arrow):not(.collapse-toggle),
+.docblock:not(.type-decl) a:not(.srclink):not(.test-arrow),
 .docblock-short a:not(.srclink):not(.test-arrow), .item-info a,
 #help a {
 	color: #D2991D;
diff --git a/src/librustdoc/html/static/themes/light.css b/src/librustdoc/html/static/themes/light.css
index 4c83879e234..9335dd96d29 100644
--- a/src/librustdoc/html/static/themes/light.css
+++ b/src/librustdoc/html/static/themes/light.css
@@ -174,7 +174,7 @@ a {
 	color: #000;
 }
 
-.docblock:not(.type-decl) a:not(.srclink):not(.test-arrow):not(.collapse-toggle),
+.docblock:not(.type-decl) a:not(.srclink):not(.test-arrow),
 .docblock-short a:not(.srclink):not(.test-arrow), .item-info a,
 #help a {
 	color: #3873AD;