rustdoc: use <wbr> in sidebar headers

This also improves sidebar layout, so instead of

    BTreeM
    ap

you get this

    BTree
    Map

Author: notriddle

src/librustdoc/html/layout.rs

@@ -69,6 +69,8 @@ struct PageLayout<'a> {
     display_krate_version_extra: &'a str,
 }
 
+pub(crate) use crate::html::render::sidebar::filters;
+
 pub(crate) fn render<T: Print, S: Print>(
     layout: &Layout,
     page: &Page<'_>,

src/librustdoc/html/render/mod.rs

@@ -30,7 +30,7 @@ mod tests;
 
 mod context;
 mod print_item;
-mod sidebar;
+pub(crate) mod sidebar;
 mod span_map;
 mod type_layout;
 mod write_shared;

src/librustdoc/html/render/sidebar.rs

@@ -77,6 +77,25 @@ impl<'a> Link<'a> {
     }
 }
 
+pub(crate) mod filters {
+    use std::fmt::Display;
+
+    use askama::{Html, MarkupDisplay};
+
+    use crate::html::escape::EscapeBodyTextWithWbr;
+    use crate::html::render::display_fn;
+    pub(crate) fn wrapped<T>(v: T) -> askama::Result<MarkupDisplay<Html, impl Display>>
+    where
+        T: Display,
+    {
+        let string = v.to_string();
+        Ok(MarkupDisplay::new_safe(
+            display_fn(move |f| EscapeBodyTextWithWbr(&string).fmt(f)),
+            Html,
+        ))
+    }
+}
+
 pub(super) fn print_sidebar(cx: &Context<'_>, it: &clean::Item, buffer: &mut Buffer) {
     let blocks: Vec<LinkBlock<'_>> = match *it.kind {
         clean::StructItem(ref s) => sidebar_struct(cx, it, s),

src/librustdoc/html/templates/page.html

@@ -98,7 +98,7 @@
             </a> {# #}
             {% endif %}
             <h2> {# #}
-                <a href="{{page.root_path|safe}}{{display_krate_with_trailing_slash|safe}}index.html">{{display_krate}}</a> {# #}
+                <a href="{{page.root_path|safe}}{{display_krate_with_trailing_slash|safe}}index.html">{{display_krate|wrapped|safe}}</a> {# #}
                 {% if !display_krate_version_number.is_empty() %}
                     <span class="version">{{+ display_krate_version_number}}</span>
                 {% endif %}

src/librustdoc/html/templates/sidebar.html

@@ -1,6 +1,6 @@
 {% if !title.is_empty() %}
     <h2 class="location"> {# #}
-        <a href="#">{{title_prefix}}{{title}}</a> {# #}
+        <a href="#">{{title_prefix}}{{title|wrapped|safe}}</a> {# #}
     </h2>
 {% endif %}
 <div class="sidebar-elems">
@@ -15,7 +15,9 @@ <h2 class="location"> {# #}
             {% for block in blocks %}
                 {% if block.should_render() %}
                     {% if !block.heading.name.is_empty() %}
-                        <h3><a href="#{{block.heading.href|safe}}">{{block.heading.name}}</a></h3>
+                        <h3><a href="#{{block.heading.href|safe}}"> {# #}
+                            {{block.heading.name|wrapped|safe}} {# #}
+                        </a></h3> {# #}
                     {% endif %}
                     {% if !block.links.is_empty() %}
                         <ul class="block{% if !block.class.is_empty() +%} {{+block.class}}{% endif %}">