Fix DOC_MARKDOWN requiring backticks on links to external websites

Author: nindalf

clippy_lints/src/doc.rs

@@ -660,6 +660,12 @@ fn check_doc<'a, Events: Iterator<Item = (pulldown_cmark::Event<'a>, Range<usize
                     check_link_quotes(cx, in_link.is_some(), trimmed_text, span, &range, begin, text.len());
                     // Adjust for the beginning of the current `Event`
                     let span = span.with_lo(span.lo() + BytePos::from_usize(range.start - begin));
+                    if let Some(link) = in_link.as_ref()
+                      && let Ok(url) = Url::parse(link)
+                      && (url.scheme() == "https" || url.scheme() == "http") {
+                        // Don't check the text associated with external URLs
+                        continue;
+                    }
                     text_to_check.push((text, span));
                 }
             },

tests/ui/doc/doc-fixable.fixed

@@ -78,7 +78,7 @@ fn test_allowed() {
 /// This test has [a `link_with_underscores`][chunked-example] inside it. See #823.
 /// See also [the issue tracker](https://github.com/rust-lang/rust-clippy/search?q=clippy::doc_markdown&type=Issues)
 /// on GitHub (which is a camel-cased word, but is OK). And here is another [inline link][inline_link].
-/// It can also be [`inline_link2`].
+/// It can also be [inline_link2]. A link to [StackOverflow](https://stackoverflow.com) is also acceptable.
 ///
 /// [chunked-example]: https://en.wikipedia.org/wiki/Chunked_transfer_encoding#Example
 /// [inline_link]: https://foobar

tests/ui/doc/doc-fixable.rs

@@ -75,10 +75,10 @@ fn test_units() {
 fn test_allowed() {
 }
 
-/// This test has [a link_with_underscores][chunked-example] inside it. See #823.
+/// This test has [a `link_with_underscores`][chunked-example] inside it. See #823.
 /// See also [the issue tracker](https://github.com/rust-lang/rust-clippy/search?q=clippy::doc_markdown&type=Issues)
 /// on GitHub (which is a camel-cased word, but is OK). And here is another [inline link][inline_link].
-/// It can also be [inline_link2].
+/// It can also be [inline_link2]. A link to [StackOverflow](https://stackoverflow.com) is also acceptable.
 ///
 /// [chunked-example]: https://en.wikipedia.org/wiki/Chunked_transfer_encoding#Example
 /// [inline_link]: https://foobar

tests/ui/doc/doc-fixable.stderr

@@ -142,28 +142,6 @@ help: try
 LL | /// `be_sure_we_got_to_the_end_of_it`
    |     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
-error: item in documentation is missing backticks
-  --> $DIR/doc-fixable.rs:78:22
-   |
-LL | /// This test has [a link_with_underscores][chunked-example] inside it. See #823.
-   |                      ^^^^^^^^^^^^^^^^^^^^^
-   |
-help: try
-   |
-LL | /// This test has [a `link_with_underscores`][chunked-example] inside it. See #823.
-   |                      ~~~~~~~~~~~~~~~~~~~~~~~
-
-error: item in documentation is missing backticks
-  --> $DIR/doc-fixable.rs:81:21
-   |
-LL | /// It can also be [inline_link2].
-   |                     ^^^^^^^^^^^^
-   |
-help: try
-   |
-LL | /// It can also be [`inline_link2`].
-   |                     ~~~~~~~~~~~~~~
-
 error: item in documentation is missing backticks
   --> $DIR/doc-fixable.rs:91:5
    |
@@ -329,5 +307,5 @@ help: try
 LL | /// An iterator over `mycrate::Collection`'s values.
    |                      ~~~~~~~~~~~~~~~~~~~~~
 
-error: aborting due to 30 previous errors
+error: aborting due to 28 previous errors