Add lint for broken doc links

CHANGELOG.md

@@ -5441,6 +5441,7 @@ Released 2018-09-13
 [`disallowed_type`]: https://rust-lang.github.io/rust-clippy/master/index.html#disallowed_type
 [`disallowed_types`]: https://rust-lang.github.io/rust-clippy/master/index.html#disallowed_types
 [`diverging_sub_expression`]: https://rust-lang.github.io/rust-clippy/master/index.html#diverging_sub_expression
+[`doc_broken_link`]: https://rust-lang.github.io/rust-clippy/master/index.html#doc_broken_link
 [`doc_lazy_continuation`]: https://rust-lang.github.io/rust-clippy/master/index.html#doc_lazy_continuation
 [`doc_link_with_quotes`]: https://rust-lang.github.io/rust-clippy/master/index.html#doc_link_with_quotes
 [`doc_markdown`]: https://rust-lang.github.io/rust-clippy/master/index.html#doc_markdown

clippy_lints/src/declared_lints.rs

@@ -135,6 +135,7 @@ pub static LINTS: &[&crate::LintInfo] = &[
     crate::disallowed_names::DISALLOWED_NAMES_INFO,
     crate::disallowed_script_idents::DISALLOWED_SCRIPT_IDENTS_INFO,
     crate::disallowed_types::DISALLOWED_TYPES_INFO,
+    crate::doc::DOC_BROKEN_LINK_INFO,
     crate::doc::DOC_LAZY_CONTINUATION_INFO,
     crate::doc::DOC_LINK_WITH_QUOTES_INFO,
     crate::doc::DOC_MARKDOWN_INFO,

clippy_lints/src/doc/broken_link.rs

@@ -0,0 +1,14 @@
+use super::{DOC_BROKEN_LINK, Fragments};
+use clippy_utils::diagnostics::span_lint;
+use rustc_lint::LateContext;
+use std::ops::Range;
+
+// Check broken links in code docs.
+pub fn check(cx: &LateContext<'_>, _trimmed_text: &str, range: Range<usize>, fragments: Fragments<'_>, link: &str) {
+    if let Some(span) = fragments.span(cx, range) {
+        // Broken links are replaced with "fake" value by `fake_broken_link_callback` at `doc/mod.rs`.
+        if link == "fake" {
+            span_lint(cx, DOC_BROKEN_LINK, span, "possible broken doc link");
+        }
+    }
+}

clippy_lints/src/doc/mod.rs

@@ -32,6 +32,7 @@ use rustc_span::{Span, sym};
 use std::ops::Range;
 use url::Url;
 
+mod broken_link;
 mod empty_line_after;
 mod link_with_quotes;
 mod markdown;
@@ -261,6 +262,33 @@ declare_clippy_lint! {
     "possible typo for an intra-doc link"
 }
 
+declare_clippy_lint! {
+    /// ### What it does
+    /// Checks the doc comments have unbroken links, mostly caused
+    /// by bad formatted links such as broken across multiple lines.
+    ///
+    /// ### Why is this bad?
+    /// Because documentation generated by rustdoc will be broken
+    /// since expected links won't be links and just text.
+    ///
+    /// ### Examples
+    /// This link is broken:
+    /// ```no_run
+    /// /// [example of a bad link](https://
+    /// /// github.com/rust-lang/rust-clippy/)
+    /// pub fn do_something() {}
+    ///
+    /// It shouldn't be broken across multiple lines to work:
+    /// ```no_run
+    /// /// [example of a good link](https://github.com/rust-lang/rust-clippy/)
+    /// pub fn do_something() {}
+    /// ```
+    #[clippy::version = "1.82.0"]
+    pub DOC_BROKEN_LINK,
+    pedantic,
+    "broken document link"
+}
+
 declare_clippy_lint! {
     /// ### What it does
     /// Checks for the doc comments of publicly visible
@@ -548,6 +576,7 @@ impl Documentation {
 
 impl_lint_pass!(Documentation => [
     DOC_LINK_WITH_QUOTES,
+    DOC_BROKEN_LINK,
     DOC_MARKDOWN,
     MISSING_SAFETY_DOC,
     MISSING_ERRORS_DOC,
@@ -929,6 +958,9 @@ fn check_doc<'a, Events: Iterator<Item = (pulldown_cmark::Event<'a>, Range<usize
                 } else {
                     if in_link.is_some() {
                         link_with_quotes::check(cx, trimmed_text, range.clone(), fragments);
+                        if let Some(link) = in_link.as_ref() {
+                            broken_link::check(cx, trimmed_text, range.clone(), fragments, &link);
+                        }
                     }
                     if let Some(link) = in_link.as_ref()
                         && let Ok(url) = Url::parse(link)

tests/ui/doc_broken_link.rs

@@ -0,0 +1,36 @@
+#![warn(clippy::doc_broken_link)]
+
+fn main() {
+    doc_valid_link();
+    doc_valid_link_broken_title();
+    doc_valid_link_broken_url_tag();
+    doc_invalid_link_broken_url_scheme_part();
+    doc_invalid_link_broken_url_host_part();
+}
+
+/// Test valid link, whole link single line.
+/// [doc valid link](https://test.fake/doc_valid_link)
+pub fn doc_valid_link() {}
+
+/// Test valid link, title tag broken across multiple lines.
+/// [doc invalid link broken
+/// title](https://test.fake/doc_valid_link_broken_title)
+pub fn doc_valid_link_broken_title() {}
+
+/// Test valid link, url tag broken across multiple lines, but
+/// the whole url part in a single line.
+/// [doc valid link broken url tag](
+/// https://test.fake/doc_valid_link_broken_url_tag)
+pub fn doc_valid_link_broken_url_tag() {}
+
+/// Test invalid link, url part broken across multiple lines.
+/// [doc invalid link broken url scheme part part](https://
+/// test.fake/doc_invalid_link_broken_url_scheme_part)
+//~^^ ERROR: possible broken doc link
+pub fn doc_invalid_link_broken_url_scheme_part() {}
+
+/// Test invalid link, url part broken across multiple lines.
+/// [doc invalid link broken url host part](https://test
+/// .fake/doc_invalid_link_broken_url_host_part)
+//~^^ ERROR: possible broken doc link
+pub fn doc_invalid_link_broken_url_host_part() {}

tests/ui/doc_broken_link.stderr

@@ -0,0 +1,17 @@
+error: possible broken doc link
+  --> tests/ui/doc_broken_link.rs:27:6
+   |
+LL | /// [doc invalid link broken url scheme part part](https://
+   |      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: `-D clippy::doc-broken-link` implied by `-D warnings`
+   = help: to override `-D warnings` add `#[allow(clippy::doc_broken_link)]`
+
+error: possible broken doc link
+  --> tests/ui/doc_broken_link.rs:33:6
+   |
+LL | /// [doc invalid link broken url host part](https://test
+   |      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to 2 previous errors
+