Rollup merge of #105539 - GuillaumeGomez:hashtag-prepended-lines-non-rust, r=notriddle

rustdoc: Only hide lines starting with `#` in rust code blocks

Fixes https://github.com/rust-lang/rust/issues/105527.

So before approving, this is a big question: in rust code blocks, in a line starts with a `#`, we hide it in the output. However, should we do the same for non-rust code blocks too? I think it's a bit problematic to do it because `#` can be used for many things but I prefer to check first with everyone (might also be worth updating documentation too).

cc ``@rust-lang/rustdoc``
r? ``@notriddle``

src/librustdoc/html/markdown.rs

@@ -246,8 +246,6 @@ fn next(&mut self) -> Option<Self::Item> {
                 _ => {}
             }
         }
-        let lines = origtext.lines().filter_map(|l| map_line(l).for_html());
-        let text = lines.intersperse("\n".into()).collect::<String>();
 
         let parse_result = match kind {
             CodeBlockKind::Fenced(ref lang) => {
@@ -260,7 +258,7 @@ fn next(&mut self) -> Option<Self::Item> {
                                  <pre class=\"language-{}\"><code>{}</code></pre>\
                              </div>",
                             lang,
-                            Escape(&text),
+                            Escape(&origtext),
                         )
                         .into(),
                     ));
@@ -270,6 +268,9 @@ fn next(&mut self) -> Option<Self::Item> {
             CodeBlockKind::Indented => Default::default(),
         };
 
+        let lines = origtext.lines().filter_map(|l| map_line(l).for_html());
+        let text = lines.intersperse("\n".into()).collect::<String>();
+
         compile_fail = parse_result.compile_fail;
         should_panic = parse_result.should_panic;
         ignore = parse_result.ignore;

src/librustdoc/html/markdown/tests.rs

@@ -309,3 +309,40 @@ fn add_test(&mut self, _test: String, _config: LangString, line: usize) {
     t("```rust\n```\n```rust\n```", &[1, 3]);
     t("```rust\n```\n ```rust\n```", &[1, 3]);
 }
+
+#[test]
+fn test_ascii_with_prepending_hashtag() {
+    fn t(input: &str, expect: &str) {
+        let mut map = IdMap::new();
+        let output = Markdown {
+            content: input,
+            links: &[],
+            ids: &mut map,
+            error_codes: ErrorCodes::Yes,
+            edition: DEFAULT_EDITION,
+            playground: &None,
+            heading_offset: HeadingOffset::H2,
+        }
+        .into_string();
+        assert_eq!(output, expect, "original: {}", input);
+    }
+
+    t(
+        r#"```ascii
+#..#.####.#....#.....##..
+#..#.#....#....#....#..#.
+####.###..#....#....#..#.
+#..#.#....#....#....#..#.
+#..#.#....#....#....#..#.
+#..#.####.####.####..##..
+```"#,
+        "<div class=\"example-wrap\"><pre class=\"language-ascii\"><code>\
+#..#.####.#....#.....##..
+#..#.#....#....#....#..#.
+####.###..#....#....#..#.
+#..#.#....#....#....#..#.
+#..#.#....#....#....#..#.
+#..#.####.####.####..##..
+</code></pre></div>",
+    );
+}