add another heirustic to source_span_for_markdown_range

Author: lolbinarycat

compiler/rustc_resolve/src/rustdoc.rs

@@ -498,20 +498,25 @@ pub fn span_of_fragments(fragments: &[DocFragment]) -> Option<Span> {
 /// This method does not always work, because markdown bytes don't necessarily match source bytes,
 /// like if escapes are used in the string. In this case, it returns `None`.
 ///
+/// `markdown` is typically the entire documentation for an item,
+/// after combining fragments.
+///
 /// This method will return `Some` only if:
 ///
 /// - The doc is made entirely from sugared doc comments, which cannot contain escapes
 /// - The doc is entirely from a single doc fragment, with a string literal, exactly equal
 /// - The doc comes from `include_str!`
+/// - The doc includes exactly one substring matching `markdown[md_range]` which is contained in a single doc fragment.
 pub fn source_span_for_markdown_range(
     tcx: TyCtxt<'_>,
     markdown: &str,
     md_range: &Range<usize>,
     fragments: &[DocFragment],
 ) -> Option<Span> {
+    let span_to_snippet = |span| tcx.sess.source_map().span_to_snippet(span);
     if let &[fragment] = &fragments
         && fragment.kind == DocFragmentKind::RawDoc
-        && let Ok(snippet) = tcx.sess.source_map().span_to_snippet(fragment.span)
+        && let Ok(snippet) = span_to_snippet(fragment.span)
         && snippet.trim_end() == markdown.trim_end()
         && let Ok(md_range_lo) = u32::try_from(md_range.start)
         && let Ok(md_range_hi) = u32::try_from(md_range.end)
@@ -528,6 +533,30 @@ pub fn source_span_for_markdown_range(
     let is_all_sugared_doc = fragments.iter().all(|frag| frag.kind == DocFragmentKind::SugaredDoc);
 
     if !is_all_sugared_doc {
+        // this case ignores the markdown outside of the range so that it can
+        // work in cases where the markdown is made from several different
+        // doc fragments, but the target range does not span across multiple
+        // fragments.
+        let mut match_data = None;
+        for (i, fragment) in fragments.iter().enumerate() {
+            if let Ok(snippet) = span_to_snippet(fragment.span)
+                && let Some(match_start) = snippet.find(&markdown[md_range.clone()])
+            {
+                if match_data.is_none() {
+                    match_data = Some((i, match_start));
+                } else {
+                    // heirustic produced ambiguity, return nothing.
+                    return None;
+                }
+            }
+        }
+        if let Some((i, match_start)) = match_data {
+            use rustc_span::BytePos;
+            let mut sp = fragments[i].span;
+            sp = sp.with_lo(sp.lo() + BytePos(match_start as u32));
+            sp = sp.with_hi(sp.lo() + BytePos((md_range.end - md_range.start) as u32));
+            return Some(sp);
+        }
         return None;
     }
 

tests/rustdoc-ui/lints/bare-urls-limit.rs

@@ -0,0 +1,12 @@
+//@ check-fail
+
+#![deny(rustdoc::bare_urls)]
+
+// examples of bare urls that are beyond our ability to generate suggestions for
+
+// this falls through every heirustic in `source_span_for_markdown_range`,
+// and thus does not get any suggestion.
+#[doc = "good: <https://example.com/> \n\n"]
+//~^ ERROR this URL is not a hyperlink
+#[doc = "bad: https://example.com/"]
+pub fn duplicate_raw() {}

tests/rustdoc-ui/lints/bare-urls-limit.stderr

@@ -0,0 +1,18 @@
+error: this URL is not a hyperlink
+  --> $DIR/bare-urls-limit.rs:9:9
+   |
+LL |   #[doc = "good: <https://example.com/> \n\n"]
+   |  _________^
+LL | |
+LL | | #[doc = "bad: https://example.com/"]
+   | |___________________________________^
+   |
+   = note: bare URLs are not automatically turned into clickable links
+note: the lint level is defined here
+  --> $DIR/bare-urls-limit.rs:3:9
+   |
+LL | #![deny(rustdoc::bare_urls)]
+   |         ^^^^^^^^^^^^^^^^^^
+
+error: aborting due to 1 previous error
+

tests/rustdoc-ui/lints/bare-urls.fixed

@@ -38,6 +38,16 @@
 //~^ ERROR this URL is not a hyperlink
 pub fn c() {}
 
+#[doc = "here's a thing: <https://example.com/>"]
+//~^ ERROR this URL is not a hyperlink
+pub fn f() {}
+
+/// <https://example.com/sugar>
+//~^ ERROR this URL is not a hyperlink
+#[doc = "<https://example.com/raw>"]
+//~^ ERROR this URL is not a hyperlink
+pub fn mixed() {}
+
 /// <https://somewhere.com>
 /// [a](http://a.com)
 /// [b]

tests/rustdoc-ui/lints/bare-urls.rs

@@ -38,6 +38,16 @@
 //~^ ERROR this URL is not a hyperlink
 pub fn c() {}
 
+#[doc = "here's a thing: https://example.com/"]
+//~^ ERROR this URL is not a hyperlink
+pub fn f() {}
+
+/// https://example.com/sugar
+//~^ ERROR this URL is not a hyperlink
+#[doc = "https://example.com/raw"]
+//~^ ERROR this URL is not a hyperlink
+pub fn mixed() {}
+
 /// <https://somewhere.com>
 /// [a](http://a.com)
 /// [b]