Rollup merge of #83337 - Manishearth:item-hide, r=GuillaumeGomez

rustdoc: Hide item contents, not items

This tweaks rustdoc to hide item contents instead of items, and only when there are too many of them.

This means that users will _always_ see the type parameters, and will _often_ see fields/etc as long as they are small. Traits have some heuristics for hiding only the methods or only the methods and the consts, since the associated types are super important.

I'm happy to play around with the heuristics here; we could potentially make it so that structs/enums/etc are always hidden but traits will try really hard to show type aliases.

This needs a test, but you can see it rendered at https://manishearth.net/sand/doc_render/bar/

<details>

<summary> Code example </summary>

```rust
pub struct PubStruct {
    pub a: usize,
    pub b: usize,
}

pub struct BigPubStruct {
    pub a: usize,
    pub b: usize,
    pub c: usize,
    pub d: usize,
    pub e: usize,
    pub f: usize,
}

pub union BigUnion {
    pub a: usize,
    pub b: usize,
    pub c: usize,
    pub d: usize,
    pub e: usize,
    pub f: usize,
}

pub union Union {
    pub a: usize,
    pub b: usize,
    pub c: usize,
}

pub struct PrivStruct {
    a: usize,
    b: usize,
}

pub enum Enum {
    A, B, C,
    D {
        a: u8,
        b: u8
    }
}

pub enum LargeEnum {
    A, B, C, D, E, F, G, H, I, J
}

pub trait Trait {
    type A;
    #[must_use]
    fn foo();
    fn bar();
}

pub trait GinormousTrait {
    type A;
    type B;
    type C;
    type D;
    type E;
    type F;
    const N: usize = 1;
    #[must_use]
    fn foo();
    fn bar();
}

pub trait HugeTrait {
    type A;
    const M: usize = 1;
    const N: usize = 1;
    const O: usize = 1;
    const P: usize = 1;
    const Q: usize = 1;
    #[must_use]
    fn foo();
    fn bar();
}

pub trait BigTrait {
    type A;
    #[must_use]
    fn foo();
    fn bar();
    fn baz();
    fn quux();
    fn frob();
    fn greeble();
}

#[macro_export]
macro_rules! foo {
    (a) => {a};
}
```

</details>

Fixes #82114

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;
@@ -486,18 +485,7 @@ fn settings(root_path: &str, suffix: &str, themes: &[StylePath]) -> Result<Strin
             ],
         )
             .into(),
-        (
-            "Auto-hide item declarations",
-            vec![
-                ("auto-hide-struct", "Auto-hide structs declaration", true),
-                ("auto-hide-enum", "Auto-hide enums declaration", false),
-                ("auto-hide-union", "Auto-hide unions declaration", true),
-                ("auto-hide-trait", "Auto-hide traits declaration", true),
-                ("auto-hide-macro", "Auto-hide macros declaration", false),
-            ],
-        )
-            .into(),
-        ("auto-hide-attributes", "Auto-hide item attributes.", true).into(),
+        ("auto-hide-large-items", "Auto-hide item contents for large items.", true).into(),
         ("auto-hide-method-docs", "Auto-hide item methods' documentation", false).into(),
         ("auto-hide-trait-implementations", "Auto-hide trait implementation documentation", true)
             .into(),
@@ -947,19 +935,21 @@ 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,
@@ -1015,35 +1005,33 @@ 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 class=\"code-attribute\">{}</div>", a);
     }
 }
 

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;
@@ -131,6 +131,26 @@ pub(super) fn print_item(cx: &Context<'_>, item: &clean::Item, buf: &mut Buffer)
     }
 }
 
+/// For large structs, enums, unions, etc, determine whether to hide their fields
+fn should_hide_fields(n_fields: usize) -> bool {
+    n_fields > 12
+}
+
+fn toggle_open(w: &mut Buffer, text: &str) {
+    write!(
+        w,
+        "<details class=\"rustdoc-toggle type-contents-toggle\">\
+            <summary class=\"hideme\">\
+                <span>Show {}</span>\
+            </summary>",
+        text
+    );
+}
+
+fn toggle_close(w: &mut Buffer) {
+    w.write_str("</details>");
+}
+
 fn item_module(w: &mut Buffer, cx: &Context<'_>, item: &clean::Item, items: &[clean::Item]) {
     document(w, cx, item, None);
 
@@ -377,7 +397,7 @@ 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 \
@@ -406,7 +426,7 @@ 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 {}{}{}",
@@ -429,17 +449,36 @@ fn item_trait(w: &mut Buffer, cx: &Context<'_>, it: &clean::Item, t: &clean::Tra
         } else {
             // FIXME: we should be using a derived_id for the Anchors here
             w.write_str("{\n");
+            let mut toggle = false;
+
+            // If there are too many associated types, hide _everything_
+            if should_hide_fields(types.len()) {
+                toggle = true;
+                toggle_open(w, "associated items");
+            }
             for t in &types {
                 render_assoc_item(w, t, AssocItemLink::Anchor(None), ItemType::Trait, cx);
                 w.write_str(";\n");
             }
+            // If there are too many associated constants, hide everything after them
+            // We also do this if the types + consts is large because otherwise we could
+            // render a bunch of types and _then_ a bunch of consts just because both were
+            // _just_ under the limit
+            if !toggle && should_hide_fields(types.len() + consts.len()) {
+                toggle = true;
+                toggle_open(w, "associated constants and methods");
+            }
             if !types.is_empty() && !consts.is_empty() {
                 w.write_str("\n");
             }
             for t in &consts {
                 render_assoc_item(w, t, AssocItemLink::Anchor(None), ItemType::Trait, cx);
                 w.write_str(";\n");
             }
+            if !toggle && should_hide_fields(required.len() + provided.len()) {
+                toggle = true;
+                toggle_open(w, "methods");
+            }
             if !consts.is_empty() && !required.is_empty() {
                 w.write_str("\n");
             }
@@ -470,6 +509,9 @@ fn item_trait(w: &mut Buffer, cx: &Context<'_>, it: &clean::Item, t: &clean::Tra
                     w.write_str("<div class=\"item-spacer\"></div>");
                 }
             }
+            if toggle {
+                toggle_close(w);
+            }
             w.write_str("}");
         }
         w.write_str("</pre>")
@@ -693,7 +735,7 @@ 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>",
@@ -714,7 +756,7 @@ 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>",
@@ -735,7 +777,7 @@ 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>",
@@ -757,7 +799,7 @@ 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>")
     });
@@ -803,7 +845,7 @@ 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 {}{}{}",
@@ -816,6 +858,10 @@ fn item_enum(w: &mut Buffer, cx: &Context<'_>, it: &clean::Item, e: &clean::Enum
             w.write_str(" {}");
         } else {
             w.write_str(" {\n");
+            let toggle = should_hide_fields(e.variants.len());
+            if toggle {
+                toggle_open(w, "variants");
+            }
             for v in &e.variants {
                 w.write_str("    ");
                 let name = v.name.as_ref().unwrap();
@@ -844,6 +890,9 @@ fn item_enum(w: &mut Buffer, cx: &Context<'_>, it: &clean::Item, e: &clean::Enum
             if e.variants_stripped {
                 w.write_str("    // some variants omitted\n");
             }
+            if toggle {
+                toggle_close(w);
+            }
             w.write_str("}");
         }
         w.write_str("</pre>")
@@ -976,7 +1025,7 @@ 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,
@@ -1015,7 +1064,7 @@ 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>")
     });
@@ -1064,7 +1113,7 @@ 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>",
@@ -1078,7 +1127,7 @@ 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>",
@@ -1171,7 +1220,7 @@ fn wrap_into_docblock<F>(w: &mut Buffer, f: F)
 where
     F: FnOnce(&mut Buffer),
 {
-    w.write_str("<div class=\"docblock type-decl hidden-by-usual-hider\">");
+    w.write_str("<div class=\"docblock type-decl\">");
     f(w);
     w.write_str("</div>")
 }
@@ -1261,6 +1310,13 @@ fn render_union(
     }
 
     write!(w, " {{\n{}", tab);
+    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");
+    }
+
     for field in fields {
         if let clean::StructFieldItem(ref ty) = *field.kind {
             write!(
@@ -1277,6 +1333,9 @@ fn render_union(
     if it.has_stripped_fields().unwrap() {
         write!(w, "    // some fields omitted\n{}", tab);
     }
+    if toggle {
+        toggle_close(w);
+    }
     w.write_str("}");
 }
 
@@ -1305,8 +1364,14 @@ fn render_struct(
             if let Some(g) = g {
                 write!(w, "{}", print_where_clause(g, cx.cache(), cx.tcx(), 0, true),)
             }
-            let mut has_visible_fields = false;
             w.write_str(" {");
+            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 {
+                toggle_open(w, "fields");
+            }
             for field in fields {
                 if let clean::StructFieldItem(ref ty) = *field.kind {
                     write!(
@@ -1317,7 +1382,6 @@ fn render_struct(
                         field.name.as_ref().unwrap(),
                         ty.print(cx.cache(), cx.tcx()),
                     );
-                    has_visible_fields = true;
                 }
             }
 
@@ -1331,6 +1395,9 @@ fn render_struct(
                 // `{ /* fields omitted */ }` to save space.
                 write!(w, " /* fields omitted */ ");
             }
+            if toggle {
+                toggle_close(w);
+            }
             w.write_str("}");
         }
         CtorKind::Fn => {