rustdoc: smartly hide associated items of traits if there are too man…

…y of them

src/librustdoc/html/render/print_item.rs

@@ -443,17 +443,36 @@ 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");
             }
@@ -484,6 +503,9 @@ 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>")
@@ -1284,9 +1306,7 @@ fn render_union(
     write!(w, " {{\n{}", tab);
     let count_fields = fields
         .iter()
-        .filter(
-            |f| if let clean::StructFieldItem(..) = *f.kind { true } else { false },
-        )
+        .filter(|f| if let clean::StructFieldItem(..) = *f.kind { true } else { false })
         .count();
     let toggle = should_hide_fields(count_fields);
     if toggle {
@@ -1343,9 +1363,7 @@ fn render_struct(
             w.write_str(" {");
             let count_fields = fields
                 .iter()
-                .filter(
-                    |f| if let clean::StructFieldItem(..) = *f.kind { true } else { false },
-                )
+                .filter(|f| if let clean::StructFieldItem(..) = *f.kind { true } else { false })
                 .count();
             let has_visible_fields = count_fields > 0;
             let toggle = should_hide_fields(count_fields);

src/librustdoc/html/static/rustdoc.css

@@ -1058,8 +1058,8 @@ h3 > .collapse-toggle, h4 > .collapse-toggle {
 	margin-top: 3px;
 }
 
-/* for enum and struct fields */
-.enum > .toggle-wrapper + .docblock, .struct > .toggle-wrapper + .docblock, .union > .toggle-wrapper + .docblock {
+/* 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;
 }
 
@@ -1785,7 +1785,7 @@ div.name.expand::before {
 .type-decl > pre > .docblock.attributes.top-attr {
 	margin-left: 1.8em !important;
 }
-.type-decl > pre > .toggle-attributes {
+.type-decl > pre .toggle-attributes {
 	margin-left: 2.2em;
 }
 .type-decl > pre > .docblock.attributes {

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

@@ -218,7 +218,7 @@ a {
 	color: #c5c5c5;
 }
 
-.docblock:not(.type-decl) a:not(.srclink):not(.test-arrow),
+.docblock:not(.type-decl) a:not(.srclink):not(.test-arrow):not(.collapse-toggle),
 .docblock-short a:not(.srclink):not(.test-arrow), .item-info a,
 #help a {
 	color: #39AFD7;

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

@@ -176,7 +176,7 @@ a {
 	color: #ddd;
 }
 
-.docblock:not(.type-decl) a:not(.srclink):not(.test-arrow),
+.docblock:not(.type-decl) a:not(.srclink):not(.test-arrow):not(.collapse-toggle),
 .docblock-short a:not(.srclink):not(.test-arrow), .item-info a,
 #help a {
 	color: #D2991D;

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

@@ -174,7 +174,7 @@ a {
 	color: #000;
 }
 
-.docblock:not(.type-decl) a:not(.srclink):not(.test-arrow),
+.docblock:not(.type-decl) a:not(.srclink):not(.test-arrow):not(.collapse-toggle),
 .docblock-short a:not(.srclink):not(.test-arrow), .item-info a,
 #help a {
 	color: #3873AD;