Rollup merge of #111946 - nicklimmm:askama-item-template-trait, r=GuillaumeGomez

rustdoc: Add `ItemTemplate` trait and related functions to avoid repetitively wrapping existing functions

Context: https://github.com/rust-lang/rust/pull/111430#discussion_r1200672507

This trait will be used extensively in performing migrations to Askama templates (tracking issue: https://github.com/rust-lang/rust/issues/108868)

src/librustdoc/html/render/print_item.rs

@@ -9,6 +9,8 @@
 use rustc_middle::ty::{self, TyCtxt};
 use rustc_span::hygiene::MacroKind;
 use rustc_span::symbol::{kw, sym, Symbol};
+use std::borrow::Borrow;
+use std::cell::{RefCell, RefMut};
 use std::cmp::Ordering;
 use std::fmt;
 use std::rc::Rc;
@@ -216,6 +218,53 @@ fn toggle_close(mut w: impl fmt::Write) {
     w.write_str("</details>").unwrap();
 }
 
+trait ItemTemplate<'a, 'cx: 'a>: askama::Template + fmt::Display {
+    fn item_and_mut_cx(&self) -> (&'a clean::Item, RefMut<'_, &'a mut Context<'cx>>);
+}
+
+fn item_template_document<'a: 'b, 'b, 'cx: 'a>(
+    templ: &'b impl ItemTemplate<'a, 'cx>,
+) -> impl fmt::Display + Captures<'a> + 'b + Captures<'cx> {
+    display_fn(move |f| {
+        let (item, mut cx) = templ.item_and_mut_cx();
+        let v = document(*cx, item, None, HeadingOffset::H2);
+        write!(f, "{v}")
+    })
+}
+
+fn item_template_document_type_layout<'a: 'b, 'b, 'cx: 'a>(
+    templ: &'b impl ItemTemplate<'a, 'cx>,
+) -> impl fmt::Display + Captures<'a> + 'b + Captures<'cx> {
+    display_fn(move |f| {
+        let (item, cx) = templ.item_and_mut_cx();
+        let def_id = item.item_id.expect_def_id();
+        let v = document_type_layout(*cx, def_id);
+        write!(f, "{v}")
+    })
+}
+
+fn item_template_render_attributes_in_pre<'a: 'b, 'b, 'cx: 'a>(
+    templ: &'b impl ItemTemplate<'a, 'cx>,
+) -> impl fmt::Display + Captures<'a> + 'b + Captures<'cx> {
+    display_fn(move |f| {
+        let (item, cx) = templ.item_and_mut_cx();
+        let tcx = cx.tcx();
+        let v = render_attributes_in_pre(item, "", tcx);
+        write!(f, "{v}")
+    })
+}
+
+fn item_template_render_assoc_items<'a: 'b, 'b, 'cx: 'a>(
+    templ: &'b impl ItemTemplate<'a, 'cx>,
+) -> impl fmt::Display + Captures<'a> + 'b + Captures<'cx> {
+    display_fn(move |f| {
+        let (item, mut cx) = templ.item_and_mut_cx();
+        let def_id = item.item_id.expect_def_id();
+        let v = render_assoc_items(*cx, item, def_id, AssocItemRender::All);
+        write!(f, "{v}")
+    })
+}
+
 fn item_module(w: &mut Buffer, cx: &mut Context<'_>, item: &clean::Item, items: &[clean::Item]) {
     write!(w, "{}", document(cx, item, None, HeadingOffset::H2));
 
@@ -1131,32 +1180,18 @@ fn item_union(w: &mut Buffer, cx: &mut Context<'_>, it: &clean::Item, s: &clean:
     #[derive(Template)]
     #[template(path = "item_union.html")]
     struct ItemUnion<'a, 'cx> {
-        cx: std::cell::RefCell<&'a mut Context<'cx>>,
+        cx: RefCell<&'a mut Context<'cx>>,
         it: &'a clean::Item,
         s: &'a clean::Union,
     }
 
+    impl<'a, 'cx: 'a> ItemTemplate<'a, 'cx> for ItemUnion<'a, 'cx> {
+        fn item_and_mut_cx(&self) -> (&'a clean::Item, RefMut<'_, &'a mut Context<'cx>>) {
+            (self.it, self.cx.borrow_mut())
+        }
+    }
+
     impl<'a, 'cx: 'a> ItemUnion<'a, 'cx> {
-        fn render_assoc_items<'b>(
-            &'b self,
-        ) -> impl fmt::Display + Captures<'a> + 'b + Captures<'cx> {
-            display_fn(move |f| {
-                let def_id = self.it.item_id.expect_def_id();
-                let mut cx = self.cx.borrow_mut();
-                let v = render_assoc_items(*cx, self.it, def_id, AssocItemRender::All);
-                write!(f, "{v}")
-            })
-        }
-        fn document_type_layout<'b>(
-            &'b self,
-        ) -> impl fmt::Display + Captures<'a> + 'b + Captures<'cx> {
-            display_fn(move |f| {
-                let def_id = self.it.item_id.expect_def_id();
-                let cx = self.cx.borrow_mut();
-                let v = document_type_layout(*cx, def_id);
-                write!(f, "{v}")
-            })
-        }
         fn render_union<'b>(&'b self) -> impl fmt::Display + Captures<'a> + 'b + Captures<'cx> {
             display_fn(move |f| {
                 let cx = self.cx.borrow_mut();
@@ -1164,22 +1199,6 @@ fn render_union<'b>(&'b self) -> impl fmt::Display + Captures<'a> + 'b + Capture
                 write!(f, "{v}")
             })
         }
-        fn render_attributes_in_pre<'b>(
-            &'b self,
-        ) -> impl fmt::Display + Captures<'a> + 'b + Captures<'cx> {
-            display_fn(move |f| {
-                let tcx = self.cx.borrow().tcx();
-                let v = render_attributes_in_pre(self.it, "", tcx);
-                write!(f, "{v}")
-            })
-        }
-        fn document<'b>(&'b self) -> impl fmt::Display + Captures<'a> + 'b + Captures<'cx> {
-            display_fn(move |f| {
-                let mut cx = self.cx.borrow_mut();
-                let v = document(*cx, self.it, None, HeadingOffset::H2);
-                write!(f, "{v}")
-            })
-        }
         fn document_field<'b>(
             &'b self,
             field: &'a clean::Item,
@@ -1219,7 +1238,7 @@ fn fields_iter(
         }
     }
 
-    ItemUnion { cx: std::cell::RefCell::new(cx), it, s }.render_into(w).unwrap();
+    ItemUnion { cx: RefCell::new(cx), it, s }.render_into(w).unwrap();
 }
 
 fn print_tuple_struct_fields<'a, 'cx: 'a>(

src/librustdoc/html/templates/item_union.html

@@ -1,8 +1,8 @@
 <pre class="rust item-decl"><code>
-    {{ self.render_attributes_in_pre() | safe }}
+    {{ self::item_template_render_attributes_in_pre(self.borrow()) | safe }}
     {{ self.render_union() | safe }}
 </code></pre>
-{{ self.document() | safe }}
+{{ self::item_template_document(self.borrow()) | safe }}
 {% if self.fields_iter().peek().is_some() %}
     <h2 id="fields" class="fields small-section-header">
         Fields<a href="#fields" class="anchor">§</a>
@@ -19,5 +19,5 @@
         {{ self.document_field(field) | safe }}
     {% endfor %}
 {% endif %}
-{{ self.render_assoc_items() | safe }}
+{{ self::item_template_render_assoc_items(self.borrow()) | safe }}
-{{ self.document_type_layout() | safe }}
+{{ self::item_template_document_type_layout(self.borrow()) | safe }}