Rollup merge of #110235 - GuillaumeGomez:fix-extend-css, r=notriddle

Fix `--extend-css` option

Fixes #110002.

The file was generated in the wrong folder so I moved it into `static.files` as it made more sense to have there instead of changing the path in the templates.

I also added a GUI test to ensure that this option won't break unexpectedly again.

3 files changed, 4 insertions, 5 deletions

diff --git a/src/bootstrap/test.rs b/src/bootstrap/test.rs
index ebba6e80f40..cc0e34c6035 100644
--- a/src/bootstrap/test.rs
+++ b/src/bootstrap/test.rs
@@ -1064,6 +1064,8 @@ impl Step for RustdocGUI {
                     cargo.env("RUSTDOCFLAGS", "-Zunstable-options --generate-link-to-definition");
                 } else if entry.file_name() == "scrape_examples" {
                     cargo.arg("-Zrustdoc-scrape-examples");
+                } else if entry.file_name() == "extend_css" {
+                    cargo.env("RUSTDOCFLAGS", &format!("--extend-css extra.css"));
                 }
                 builder.run(&mut cargo);
             }
diff --git a/src/doc/rustdoc/src/command-line-arguments.md b/src/doc/rustdoc/src/command-line-arguments.md
index 2a2e51b2f63..dfc80426372 100644
--- a/src/doc/rustdoc/src/command-line-arguments.md
+++ b/src/doc/rustdoc/src/command-line-arguments.md
@@ -320,10 +320,7 @@ $ rustdoc src/lib.rs --extend-css extra.css
 ```
 
 With this flag, the contents of the files you pass are included at the bottom
-of Rustdoc's `theme.css` file.
-
-While this flag is stable, the contents of `theme.css` are not, so be careful!
-Updates may break your theme extensions.
+of the `theme.css` file.
 
 ## `--sysroot`: override the system root
 
diff --git a/src/librustdoc/html/templates/page.html b/src/librustdoc/html/templates/page.html
index 532660e3d33..9133f899af6 100644
--- a/src/librustdoc/html/templates/page.html
+++ b/src/librustdoc/html/templates/page.html
@@ -64,7 +64,7 @@
     </noscript> {# #}
     {% if layout.css_file_extension.is_some() %}
         <link rel="stylesheet" {#+ #}
-            href="{{static_root_path|safe}}theme{{page.resource_suffix}}.css"> {# #}
+            href="{{page.root_path|safe}}theme{{page.resource_suffix}}.css"> {# #}
     {% endif %}
     {% if !layout.favicon.is_empty() %}
         <link rel="icon" href="{{layout.favicon}}"> {# #}