[rustdoc] Add new --book-location option to add a link to associated guide and generate it if local

src/doc/rustdoc/src/unstable-features.md

@@ -830,3 +830,11 @@ will be split as follows:
     "you today?",
 ]
 ```
+
+## Generating link to guide
+
+You can generate a link to a guide or generate the guide with `mdbook` using the `--book-location`
+command line argument. It accepts either a URL or a path. If a path is provided, the book will
+be generated.
+
+In both cases, a link to the book will be added in the sidebar at the crate level documentation.

src/librustdoc/Cargo.toml

@@ -13,6 +13,7 @@ askama = { version = "0.13", default-features = false, features = ["alloc", "con
 base64 = "0.21.7"
 itertools = "0.12"
 indexmap = "2"
+mdbook = "0.4.48"
 minifier = { version = "0.3.5", default-features = false }
 pulldown-cmark-old = { version = "0.9.6", package = "pulldown-cmark", default-features = false }
 pulldown-cmark-escape = { version = "0.11.0", features = ["simd"] }

src/librustdoc/config.rs

@@ -229,6 +229,22 @@ impl fmt::Debug for Options {
     }
 }
 
+#[derive(Clone, Debug)]
+pub(crate) enum PathOrURL {
+    Path(PathBuf),
+    URL(String),
+}
+
+impl PathOrURL {
+    fn new(s: String) -> Self {
+        if s.starts_with("https://") || s.starts_with("http://") {
+            Self::URL(s)
+        } else {
+            Self::Path(s.into())
+        }
+    }
+}
+
 /// Configuration options for the HTML page-creation process.
 #[derive(Clone, Debug)]
 pub(crate) struct RenderOptions {
@@ -310,6 +326,8 @@ pub(crate) struct RenderOptions {
     pub(crate) parts_out_dir: Option<PathToParts>,
     /// disable minification of CSS/JS
     pub(crate) disable_minification: bool,
+    /// Location where the associated book is located.
+    pub(crate) book_location: Option<PathOrURL>,
 }
 
 #[derive(Copy, Clone, Debug, PartialEq, Eq)]
@@ -814,6 +832,7 @@ impl Options {
             rustc_feature::UnstableFeatures::from_environment(crate_name.as_deref());
 
         let disable_minification = matches.opt_present("disable-minification");
+        let book_location = matches.opt_str("book-location").map(PathOrURL::new);
 
         let options = Options {
             bin_crate,
@@ -893,6 +912,7 @@ impl Options {
             include_parts_dir,
             parts_out_dir,
             disable_minification,
+            book_location,
         };
         Some((input, options, render_options))
     }

src/librustdoc/html/markdown.rs

@@ -2061,6 +2061,7 @@ fn is_default_id(id: &str) -> bool {
         | "copy-path"
         | "rustdoc-toc"
         | "rustdoc-modnav"
+        | "book-loc"
         // This is the list of IDs used by rustdoc sections (but still generated by
         // rustdoc).
         | "fields"

src/librustdoc/html/render/context.rs

@@ -146,6 +146,7 @@ pub(crate) struct SharedContext<'tcx> {
     /// Controls whether we read / write to cci files in the doc root. Defaults read=true,
     /// write=true
     should_merge: ShouldMerge,
+    pub(crate) book_location: Option<crate::config::PathOrURL>,
 }
 
 impl SharedContext<'_> {
@@ -489,6 +490,7 @@ impl<'tcx> FormatRenderer<'tcx> for Context<'tcx> {
             call_locations,
             no_emit_shared,
             html_no_source,
+            book_location,
             ..
         } = options;
 
@@ -575,6 +577,7 @@ impl<'tcx> FormatRenderer<'tcx> for Context<'tcx> {
             cache,
             call_locations,
             should_merge: options.should_merge,
+            book_location,
         };
 
         let dst = output;
@@ -646,6 +649,7 @@ impl<'tcx> FormatRenderer<'tcx> for Context<'tcx> {
             parent_is_crate: false,
             blocks: vec![blocks],
             path: String::new(),
+            book_location: shared.book_location.as_ref(),
         };
 
         bar.render_into(&mut sidebar).unwrap();

src/librustdoc/html/render/sidebar.rs

@@ -42,6 +42,7 @@ pub(super) struct Sidebar<'a> {
     pub(super) is_mod: bool,
     pub(super) blocks: Vec<LinkBlock<'a>>,
     pub(super) path: String,
+    pub(super) book_location: Option<&'a crate::config::PathOrURL>,
 }
 
 impl Sidebar<'_> {
@@ -194,6 +195,7 @@ pub(super) fn print_sidebar(cx: &Context<'_>, it: &clean::Item, buffer: &mut Str
         parent_is_crate: sidebar_path.len() == 1,
         blocks,
         path,
+        book_location: cx.shared.book_location.as_ref(),
     };
     sidebar.render_into(buffer).unwrap();
 }

src/librustdoc/html/static/css/noscript.css

@@ -135,6 +135,7 @@ nav.sub {
 	--scrape-example-code-wrapper-background-end: rgba(255, 255, 255, 0);
 	--sidebar-resizer-hover: hsl(207, 90%, 66%);
 	--sidebar-resizer-active: hsl(207, 90%, 54%);
+	--book-img-filter: invert(0%);
 }
 /* End theme: light */
 
@@ -244,6 +245,7 @@ nav.sub {
 		--scrape-example-code-wrapper-background-end: rgba(53, 53, 53, 0);
 		--sidebar-resizer-hover: hsl(207, 30%, 54%);
 		--sidebar-resizer-active: hsl(207, 90%, 54%);
+		--book-img-filter: invert(80%);
 	}
 /* End theme: dark */
 }

src/librustdoc/html/static/css/rustdoc.css

@@ -833,6 +833,27 @@ ul.block, .block li, .block ul {
 	margin-bottom: 1rem;
 }
 
+.sidebar .book {
+	display: flex;
+}
+
+.book::before {
+	width: 1em;
+	height: 1em;
+	/* Font Awesome Free 6.7.2 by @fontawesome - https://fontawesome.com License -
+	https://fontawesome.com/license/free Copyright 2025 Fonticons, Inc.*/
+	content: url('data:image/svg+xml,<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 448 512">\
+		<path d="M96 0C43 0 0 43 0 96L0 416c0 53 43 96 96 96l288 0 32 0c17.7 0 32-14.3 \
+		32-32s-14.3-32-32-32l0-64c17.7 0 32-14.3 32-32l0-320c0-17.7-14.3-32-32-32L384 0 96 0zm0 \
+		384l256 0 0 64L96 448c-17.7 0-32-14.3-32-32s14.3-32 32-32zm32-240c0-8.8 7.2-16 16-16l192 \
+		0c8.8 0 16 7.2 16 16s-7.2 16-16 16l-192 0c-8.8 0-16-7.2-16-16zm16 48l192 0c8.8 0 16 7.2 16 \
+		16s-7.2 16-16 16l-192 0c-8.8 0-16-7.2-16-16s7.2-16 16-16z"/></svg>');
+	display: block;
+	margin-right: 6px;
+	padding-top: 3px;
+	filter: var(--book-img-filter);
+}
+
 .mobile-topbar {
 	display: none;
 }
@@ -2985,6 +3006,7 @@ by default.
 	--scrape-example-code-wrapper-background-end: rgba(255, 255, 255, 0);
 	--sidebar-resizer-hover: hsl(207, 90%, 66%);
 	--sidebar-resizer-active: hsl(207, 90%, 54%);
+	--book-img-filter: invert(0%);
 }
 /* End theme: light */
 
@@ -3093,6 +3115,7 @@ by default.
 	--scrape-example-code-wrapper-background-end: rgba(53, 53, 53, 0);
 	--sidebar-resizer-hover: hsl(207, 30%, 54%);
 	--sidebar-resizer-active: hsl(207, 90%, 54%);
+	--book-img-filter: invert(80%);
 }
 /* End theme: dark */
 
@@ -3205,6 +3228,7 @@ Original by Dempfi (https://github.com/dempfi/ayu)
 	--scrape-example-code-wrapper-background-end: rgba(15, 20, 25, 0);
 	--sidebar-resizer-hover: hsl(34, 50%, 33%);
 	--sidebar-resizer-active: hsl(34, 100%, 66%);
+	--book-img-filter: invert(100%);
 }
 
 :root[data-theme="ayu"] h1,

src/librustdoc/html/templates/sidebar.html

@@ -1,5 +1,19 @@
 <div class="sidebar-elems">
     {% if is_crate %}
+        {% if let Some(book_location) = book_location %}
+            <ul class="block"> {# #}
+                <li> {# #}
+                    <h3> {# #}
+                        <a id="book-loc" class="book" href="
+                            {% match book_location %}
+                                {% when crate::config::PathOrURL::Path(s) %}{{s.display()}}
+                                {% when crate::config::PathOrURL::URL(s) %}{{s}}
+                            {% endmatch %}
+                        ">Book</a> {# #}
+                    </h3> {# #}
+                </li> {# #}
+            </ul>
+        {% endif %}
         <ul class="block"> {# #}
             <li><a id="all-types" href="all.html">All Items</a></li> {# #}
         </ul>

src/librustdoc/lib.rs

@@ -658,6 +658,14 @@ fn opts() -> Vec<RustcOptGroup> {
             "disable the minification of CSS/JS files (perma-unstable, do not use with cached files)",
             "",
         ),
+        opt(
+            Unstable,
+            Opt,
+            "",
+            "book-location",
+            "URL where the book is hosted or the folder where the mdBook source is located",
+            "PATH or URL",
+        ),
         // deprecated / removed options
         opt(
             Stable,
@@ -741,6 +749,32 @@ fn run_renderer<'tcx, T: formats::FormatRenderer<'tcx>>(
     }
 }
 
+fn generate_book(render_options: &mut config::RenderOptions) -> Result<(), String> {
+    let Some(config::PathOrURL::Path(ref mut book_dir)) = render_options.book_location else {
+        return Ok(());
+    };
+    if !book_dir.is_dir() {
+        return Err(format!(
+            "`{}` is not a folder, expected a folder or a URL for `--book-location` argument",
+            book_dir.display(),
+        ));
+    }
+    let mut book = match mdbook::MDBook::load(&book_dir) {
+        Ok(book) => book,
+        Err(error) => return Err(format!("failed to load book: {error:?}")),
+    };
+    let output_dir = render_options.output.join("doc-book");
+    *book_dir = output_dir.join("index.html");
+    book.config.build.build_dir = output_dir;
+    if let Err(error) = book.build() {
+        return Err(format!(
+            "failed to generate book into `{}`: {error:?}",
+            book.config.build.build_dir.display()
+        ));
+    }
+    Ok(())
+}
+
 /// Renders and writes cross-crate info files, like the search index. This function exists so that
 /// we can run rustdoc without a crate root in the `--merge=finalize` mode. Cross-crate info files
 /// discovered via `--include-parts-dir` are combined and written to the doc root.
@@ -793,7 +827,7 @@ fn main_args(early_dcx: &mut EarlyDiagCtxt, at_args: &[String]) {
 
     // Note that we discard any distinction between different non-zero exit
     // codes from `from_matches` here.
-    let (input, options, render_options) =
+    let (input, options, mut render_options) =
         match config::Options::from_matches(early_dcx, &matches, args) {
             Some(opts) => opts,
             None => return,
@@ -857,6 +891,10 @@ fn main_args(early_dcx: &mut EarlyDiagCtxt, at_args: &[String]) {
     let scrape_examples_options = options.scrape_examples_options.clone();
     let bin_crate = options.bin_crate;
 
+    if let Err(error) = generate_book(&mut render_options) {
+        early_dcx.early_fatal(error);
+    }
+
     let config = core::create_config(input, options, &render_options);
 
     let registered_lints = config.register_lints.is_some();

src/tools/tidy/src/deps.rs

@@ -28,6 +28,7 @@ const LICENSES: &[&str] = &[
     "Apache-2.0",
     "Apache-2.0/MIT",
     "BSD-2-Clause OR Apache-2.0 OR MIT",                   // zerocopy
+    "CC0-1.0",                                             // notify
     "ISC",
     "MIT / Apache-2.0",
     "MIT AND (MIT OR Apache-2.0)",
@@ -38,6 +39,7 @@ const LICENSES: &[&str] = &[
     "MIT OR Zlib OR Apache-2.0",                           // miniz_oxide
     "MIT",
     "MIT/Apache-2.0",
+    "MPL-2.0",                                             // mdbook
     "Unicode-3.0",                                         // icu4x
     "Unicode-DFS-2016",                                    // tinystr
     "Unlicense OR MIT",

tests/run-make/rustdoc-default-output/output-default.stdout

@@ -196,6 +196,9 @@ Options:
         --disable-minification 
                         disable the minification of CSS/JS files
                         (perma-unstable, do not use with cached files)
+        --book-location PATH or URL
+                        URL where the book is hosted or the folder where the
+                        mdBook source is located
         --plugin-path DIR
                         removed, see issue #44136
                         <https://github.com/rust-lang/rust/issues/44136> for

tests/rustdoc/book-location.rs

@@ -0,0 +1,7 @@
+//@ compile-flags: -Zunstable-options --book-location https://somewhere.world
+
+#![crate_name = "foo"]
+
+//@ has 'foo/index.html'
+//@ has - '//*[@id="book-loc"]' 'Book'
+//@ has - '//*[@href="https://somewhere.world"]' 'Book'