Rollup merge of #117869 - GuillaumeGomez:comment-highlighting-item-de…

…cl, r=notriddle

[rustdoc] Add highlighting for comments in items declaration

Fixes #117555.

So after the discussion in #117643, the outcome was that having the comments in the item declaration at the same level (in term of color) as the rest of the code was actually a bit distracting and could be improved.

The current highlighting color for comments is "lighter" than the rest and I think it fits perfectly to improve the current situation. With this, we now have different "levels" which makes it easier to read and filter out what we want when reading the items declaration.

Here's a screenshot:

![image](https://github.com/rust-lang/rust/assets/3050060/dbd98029-e98b-4997-9a89-6b823eaac9a4)

r? `@notriddle`

src/librustdoc/html/render/print_item.rs

@@ -1509,7 +1509,7 @@ fn print_tuple_struct_fields<'a, 'cx: 'a>(
                 matches!(*field.kind, clean::StrippedItem(box clean::StructFieldItem(..)))
             })
         {
-            return f.write_str("/* private fields */");
+            return f.write_str("<span class=\"comment\">/* private fields */</span>");
         }
 
         for (i, ty) in s.iter().enumerate() {
@@ -1666,7 +1666,7 @@ fn render_enum_fields(
         }
 
         if variants_stripped && !is_non_exhaustive {
-            w.write_str("    // some variants omitted\n");
+            w.write_str("    <span class=\"comment\">// some variants omitted</span>\n");
         }
         if toggle {
             toggle_close(&mut w);
@@ -1811,15 +1811,21 @@ fn item_proc_macro(
         let name = it.name.expect("proc-macros always have names");
         match m.kind {
             MacroKind::Bang => {
-                write!(buffer, "{name}!() {{ /* proc-macro */ }}").unwrap();
+                write!(buffer, "{name}!() {{ <span class=\"comment\">/* proc-macro */</span> }}")
+                    .unwrap();
             }
             MacroKind::Attr => {
                 write!(buffer, "#[{name}]").unwrap();
             }
             MacroKind::Derive => {
                 write!(buffer, "#[derive({name})]").unwrap();
                 if !m.helpers.is_empty() {
-                    buffer.write_str("\n{\n    // Attributes available to this derive:\n").unwrap();
+                    buffer
+                        .write_str(
+                            "\n{\n    \
+                        <span class=\"comment\">// Attributes available to this derive:</span>\n",
+                        )
+                        .unwrap();
                     for attr in &m.helpers {
                         writeln!(buffer, "    #[{attr}]").unwrap();
                     }
@@ -2181,7 +2187,7 @@ fn render_union<'a, 'cx: 'a>(
         }
 
         if it.has_stripped_entries().unwrap() {
-            write!(f, "    /* private fields */\n")?;
+            write!(f, "    <span class=\"comment\">/* private fields */</span>\n")?;
         }
         if toggle {
             toggle_close(&mut f);
@@ -2267,11 +2273,11 @@ fn render_struct_fields(
 
             if has_visible_fields {
                 if has_stripped_entries {
-                    write!(w, "\n{tab}    /* private fields */");
+                    write!(w, "\n{tab}    <span class=\"comment\">/* private fields */</span>");
                 }
                 write!(w, "\n{tab}");
             } else if has_stripped_entries {
-                write!(w, " /* private fields */ ");
+                write!(w, " <span class=\"comment\">/* private fields */</span> ");
             }
             if toggle {
                 toggle_close(&mut w);
@@ -2285,7 +2291,7 @@ fn render_struct_fields(
                     matches!(*field.kind, clean::StrippedItem(box clean::StructFieldItem(..)))
                 })
             {
-                write!(w, "/* private fields */");
+                write!(w, "<span class=\"comment\">/* private fields */</span>");
             } else {
                 for (i, field) in fields.iter().enumerate() {
                     if i > 0 {

tests/rustdoc-gui/item-decl-comment-highlighting.goml

@@ -0,0 +1,73 @@
+// This test checks that comments in item declarations are highlighted.
+go-to: "file://" + |DOC_PATH| + "/test_docs/private/enum.Enum.html"
+show-text: true
+
+define-function: (
+    "check-item-decl-comment",
+    (theme, url, comment_color),
+    block {
+        go-to: |url|
+        set-local-storage: {"rustdoc-theme": |theme|, "rustdoc-use-system-theme": "false"}
+        reload:
+        assert-css: (".item-decl .comment", {"color": |comment_color|}, ALL)
+    }
+)
+
+define-function: (
+    "check-items-for-theme",
+    (theme, comment_color),
+    block {
+        call-function: ("check-item-decl-comment", {
+            "theme": |theme|,
+            "url": "file://" + |DOC_PATH| + "/test_docs/private/enum.Enum.html",
+            "comment_color": |comment_color|,
+        })
+        call-function: ("check-item-decl-comment", {
+            "theme": |theme|,
+            "url": "file://" + |DOC_PATH| + "/test_docs/private/struct.Struct.html",
+            "comment_color": |comment_color|,
+        })
+        call-function: ("check-item-decl-comment", {
+            "theme": |theme|,
+            "url": "file://" + |DOC_PATH| + "/test_docs/private/struct.Tuple.html",
+            "comment_color": |comment_color|,
+        })
+        call-function: ("check-item-decl-comment", {
+            "theme": |theme|,
+            "url": "file://" + |DOC_PATH| + "/test_docs/private/union.Union.html",
+            "comment_color": |comment_color|,
+        })
+        call-function: ("check-item-decl-comment", {
+            "theme": |theme|,
+            "url": "file://" + |DOC_PATH| + "/proc_macro_test/macro.make_answer.html",
+            "comment_color": |comment_color|,
+        })
+        call-function: ("check-item-decl-comment", {
+            "theme": |theme|,
+            "url": "file://" + |DOC_PATH| + "/proc_macro_test/derive.HelperAttr.html",
+            "comment_color": |comment_color|,
+        })
+    }
+)
+
+call-function: (
+    "check-items-for-theme",
+    {
+        "theme": "ayu",
+        "comment_color": "#788797",
+    }
+)
+call-function: (
+    "check-items-for-theme",
+    {
+        "theme": "dark",
+        "comment_color": "#8d8d8b",
+    }
+)
+call-function: (
+    "check-items-for-theme",
+    {
+        "theme": "light",
+        "comment_color": "#8e908c",
+    }
+)

tests/rustdoc-gui/sidebar-source-code.goml

@@ -73,7 +73,7 @@ assert: "//*[@class='dir-entry' and @open]/*[text()='sub_mod']"
 // Only "another_folder" should be "open" in "lib2".
 assert: "//*[@class='dir-entry' and not(@open)]/*[text()='another_mod']"
 // All other trees should be collapsed.
-assert-count: ("//*[@id='src-sidebar']/details[not(text()='lib2') and not(@open)]", 10)
+assert-count: ("//*[@id='src-sidebar']/details[not(text()='lib2') and not(@open)]", 11)
 
 // We now switch to mobile mode.
 set-window-size: (600, 600)

tests/rustdoc-gui/src/proc_macro_test/Cargo.lock

@@ -0,0 +1,7 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 3
+
+[[package]]
+name = "proc_macro_test"
+version = "0.1.0"

tests/rustdoc-gui/src/proc_macro_test/Cargo.toml

@@ -0,0 +1,8 @@
+[package]
+name = "proc_macro_test"
+version = "0.1.0"
+edition = "2021"
+
+[lib]
+path = "lib.rs"
+proc-macro = true

tests/rustdoc-gui/src/proc_macro_test/lib.rs

@@ -0,0 +1,11 @@
+use proc_macro::TokenStream;
+
+#[proc_macro]
+pub fn make_answer(_item: TokenStream) -> TokenStream {
+    "fn answer() -> u32 { 42 }".parse().unwrap()
+}
+
+#[proc_macro_derive(HelperAttr, attributes(helper))]
+pub fn derive_helper_attr(_item: TokenStream) -> TokenStream {
+    TokenStream::new()
+}

tests/rustdoc-gui/src/test_docs/lib.rs

@@ -593,3 +593,21 @@ pub mod foreign_impl_order {
         fn f(&mut self, fg: [u8; 3]) {}
     }
 }
+
+pub mod private {
+    pub struct Tuple(u32, u8);
+    pub struct Struct {
+        a: u8,
+    }
+
+    pub union Union {
+        a: u8,
+        b: u16,
+    }
+
+    pub enum Enum {
+        A,
+        #[doc(hidden)]
+        B,
+    }
+}

tests/rustdoc/where.SWhere_Simd_item-decl.html

@@ -1,3 +1,3 @@
-<pre class="rust item-decl"><code>pub struct Simd&lt;T&gt;(/* private fields */)
+<pre class="rust item-decl"><code>pub struct Simd&lt;T&gt;(<span class="comment">/* private fields */</span>)
 <span class="where">where
-    T: <a class="trait" href="trait.MyTrait.html" title="trait foo::MyTrait">MyTrait</a></span>;</code></pre>
+    T: <a class="trait" href="trait.MyTrait.html" title="trait foo::MyTrait">MyTrait</a></span>;</code></pre>

tests/rustdoc/where.alpha_trait_decl.html

@@ -1,3 +1,3 @@
-<code>pub struct Alpha&lt;A&gt;(/* private fields */)
+<code>pub struct Alpha&lt;A&gt;(<span class="comment">/* private fields */</span>)
 <span class="where">where
     A: <a class="trait" href="trait.MyTrait.html" title="trait foo::MyTrait">MyTrait</a></span>;</code>

tests/rustdoc/whitespace-after-where-clause.union.html

@@ -1,4 +1,4 @@
 <pre class="rust item-decl"><code>pub union Union&lt;'a, B&gt;<div class="where">where
     B: <a class="trait" href="trait.ToOwned.html" title="trait foo::ToOwned">ToOwned</a>&lt;<a class="primitive" href="{{channel}}/std/primitive.unit.html">()</a>&gt; + ?<a class="trait" href="{{channel}}/core/marker/trait.Sized.html" title="trait core::marker::Sized">Sized</a> + 'a,</div>{
-    /* private fields */
+    <span class="comment">/* private fields */</span>
 }</code></pre>

tests/rustdoc/whitespace-after-where-clause.union2.html

@@ -1,3 +1,3 @@
 <pre class="rust item-decl"><code>pub union Union2&lt;'a, B: ?<a class="trait" href="{{channel}}/core/marker/trait.Sized.html" title="trait core::marker::Sized">Sized</a> + <a class="trait" href="trait.ToOwned.html" title="trait foo::ToOwned">ToOwned</a>&lt;<a class="primitive" href="{{channel}}/std/primitive.unit.html">()</a>&gt; + 'a&gt; {
-    /* private fields */
+    <span class="comment">/* private fields */</span>
 }</code></pre>