rustdoc's automatic link suggestion is syntactically invalid when the link is in a #[doc] attribute

[Fulgen301]

#[doc = "https://rust-lang.org"]
pub fn doc_attribute() {}

/// https://rust-lang.org
pub fn doc_comment() {}

Running rustdoc on that code produces the following output:

warning: this URL is not a hyperlink
 --> issue.rs:1:9
  |
1 | #[doc = "https://rust-lang.org"]
  |         ^^^^^^^^^^^^^^^^^^^^^^^
  |
  = note: bare URLs are not automatically turned into clickable links
  = note: `#[warn(rustdoc::bare_urls)]` on by default
help: use an automatic link instead
  |
1 | #[doc = <"https://rust-lang.org">]
  |         +                       +

warning: this URL is not a hyperlink
 --> issue.rs:4:5
  |
4 | /// https://rust-lang.org
  |     ^^^^^^^^^^^^^^^^^^^^^
  |
  = note: bare URLs are not automatically turned into clickable links
help: use an automatic link instead
  |
4 | /// <https://rust-lang.org>
  |     +                     +

warning: 2 warnings emitted

The replacement suggestion is correct for the link in the doc comment, but syntactically incorrect for the one in the #[doc] attribute - it should suggest #[doc = "<https://rust-lang.org>"] instead.

The bug happens on both stable (rustdoc 1.84.0 (9fc6b4312 2025-01-07)) and nightly (rustdoc 1.86.0-nightly (f3d1d47fd 2025-01-20)).

[linyihai]

Hi, I maybe found the outmost codes that thriggered this issue

rust/src/librustdoc/passes/lint/bare_urls.rs

Lines 19 to 35 in 22a220a

	pub(super) fn visit_item(cx: &DocContext<'_>, item: &Item, hir_id: HirId, dox: &str) {
	let report_diag = |cx: &DocContext<'_>, msg: &'static str, range: Range<usize>| {
	let sp = source_span_for_markdown_range(cx.tcx, dox, &range, &item.attrs.doc_strings)
	.unwrap_or_else(|| item.attr_span(cx.tcx));
	cx.tcx.node_span_lint(crate::lint::BARE_URLS, hir_id, sp, |lint| {
	lint.primary_message(msg)
	.note("bare URLs are not automatically turned into clickable links")
	.multipart_suggestion(
	"use an automatic link instead",
	vec![
	(sp.shrink_to_lo(), "<".to_string()),
	(sp.shrink_to_hi(), ">".to_string()),
	],
	Applicability::MachineApplicable,
	);
	});
	};

For the raw doc, the sp includes the double quotation marks(like "https:://somewhere.com", not https:://somewhere.com). I did a hack solution to drop the double quotation marks

            let mut sp = sp;
            if let Some(frame) = &item.attrs.doc_strings.first()
                && frame.kind == DocFragmentKind::RawDoc
            {
                sp = sp.with_lo(sp.lo() + BytePos(1));
                sp = sp.with_hi(sp.hi() - BytePos(1));
            }

I'm not sure it's deserve to submit a PR bases on this hack solution.

[lolbinarycat]

I belive this is because of the limitations of source_span_for_markdown_range

[lolbinarycat]

oh yeah the current system is extremely broken if there's even a single #[doc] attribute.