Rollup merge of #112740 - GuillaumeGomez:link-to-search-chapter, r=notriddle

Add link to rustdoc book search chapter in help popover

One thing that was missing in the rustdoc output and its help popover was a link back to the search feature chapter in the rustdoc book.

It looks like this:

![image](https://github.com/rust-lang/rust/assets/3050060/425413e5-e734-4d40-b675-8b2dcef874a2)

r? `@notriddle`

4 files changed, 12 insertions, 2 deletions

diff --git a/src/librustdoc/clean/utils.rs b/src/librustdoc/clean/utils.rs
index 294de12cea8..f375f0efbd1 100644
--- a/src/librustdoc/clean/utils.rs
+++ b/src/librustdoc/clean/utils.rs
@@ -21,6 +21,7 @@ use rustc_middle::ty::{self, TyCtxt};
 use rustc_span::symbol::{kw, sym, Symbol};
 use std::fmt::Write as _;
 use std::mem;
+use std::sync::LazyLock as Lazy;
 use thin_vec::{thin_vec, ThinVec};
 
 #[cfg(test)]
@@ -582,6 +583,8 @@ pub(crate) fn has_doc_flag(tcx: TyCtxt<'_>, did: DefId, flag: Symbol) -> bool {
 ///
 /// Set by `bootstrap::Builder::doc_rust_lang_org_channel` in order to keep tests passing on beta/stable.
 pub(crate) const DOC_RUST_LANG_ORG_CHANNEL: &str = env!("DOC_RUST_LANG_ORG_CHANNEL");
+pub(crate) static DOC_CHANNEL: Lazy<&'static str> =
+    Lazy::new(|| DOC_RUST_LANG_ORG_CHANNEL.rsplit("/").filter(|c| !c.is_empty()).next().unwrap());
 
 /// Render a sequence of macro arms in a format suitable for displaying to the user
 /// as part of an item declaration.
diff --git a/src/librustdoc/html/layout.rs b/src/librustdoc/html/layout.rs
index 6ab849c92a0..8c5871d9126 100644
--- a/src/librustdoc/html/layout.rs
+++ b/src/librustdoc/html/layout.rs
@@ -55,6 +55,7 @@ struct PageLayout<'a> {
     sidebar: String,
     content: String,
     krate_with_trailing_slash: String,
+    rust_channel: &'static str,
     pub(crate) rustdoc_version: &'a str,
 }
 
@@ -82,6 +83,7 @@ pub(crate) fn render<T: Print, S: Print>(
         sidebar,
         content,
         krate_with_trailing_slash,
+        rust_channel: *crate::clean::utils::DOC_CHANNEL,
         rustdoc_version,
     }
     .render()
diff --git a/src/librustdoc/html/static/js/main.js b/src/librustdoc/html/static/js/main.js
index f5296abaee6..254b0d8bf5a 100644
--- a/src/librustdoc/html/static/js/main.js
+++ b/src/librustdoc/html/static/js/main.js
@@ -1050,9 +1050,10 @@ function preLoadCss(cssUrl) {
 
     function buildHelpMenu() {
         const book_info = document.createElement("span");
+        const channel = getVar("channel");
         book_info.className = "top";
-        book_info.innerHTML = "You can find more information in \
-            <a href=\"https://doc.rust-lang.org/rustdoc/\">the rustdoc book</a>.";
+        book_info.innerHTML = `You can find more information in \
+<a href="https://doc.rust-lang.org/${channel}/rustdoc/">the rustdoc book</a>.`;
 
         const shortcuts = [
             ["?", "Show this help dialog"],
@@ -1072,6 +1073,9 @@ function preLoadCss(cssUrl) {
         div_shortcuts.innerHTML = "<h2>Keyboard Shortcuts</h2><dl>" + shortcuts + "</dl></div>";
 
         const infos = [
+            `For a full list of all search features, take a look <a \
+href="https://doc.rust-lang.org/${channel}/rustdoc/how-to-read-rustdoc.html\
+#the-search-interface">here</a>.`,
             "Prefix searches with a type followed by a colon (e.g., <code>fn:</code>) to \
              restrict the search to a given item kind.",
             "Accepted kinds are: <code>fn</code>, <code>mod</code>, <code>struct</code>, \
diff --git a/src/librustdoc/html/templates/page.html b/src/librustdoc/html/templates/page.html
index 9133f899af6..759c4fd6012 100644
--- a/src/librustdoc/html/templates/page.html
+++ b/src/librustdoc/html/templates/page.html
@@ -31,6 +31,7 @@
          data-themes="{{themes|join(",") }}" {#+ #}
          data-resource-suffix="{{page.resource_suffix}}" {#+ #}
          data-rustdoc-version="{{rustdoc_version}}" {#+ #}
+         data-channel="{{rust_channel}}" {#+ #}
          data-search-js="{{files.search_js}}" {#+ #}
          data-settings-js="{{files.settings_js}}" {#+ #}
          data-settings-css="{{files.settings_css}}" {#+ #}