fix: Escape double quotes in link titles. (#62)

Byron · Nov 24, 2023 · 9a64f6b · 9a64f6b
2 parents b1f77e0 + 4767b2f
commit 9a64f6b
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Showing 2 changed files with 54 additions and 2 deletions.
diff --git a/src/lib.rs b/src/lib.rs
@@ -3,7 +3,7 @@
 use std::{
     borrow::{Borrow, Cow},
     collections::HashSet,
-    fmt,
+    fmt::{self, Write},
 };
 
 use pulldown_cmark::{Alignment as TableAlignment, Event, HeadingLevel, LinkType};
@@ -588,7 +588,7 @@ where
         write!(f, "]{}{uri}", separator, uri = uri)?;
     }
     if !title.is_empty() {
-        write!(f, " \"{title}\"", title = title)?;
+        write!(f, " \"{title}\"", title = EscapeLinkTitle(title))?;
     }
     if link_type != LinkType::Shortcut {
         f.write_char(')')?;
@@ -597,6 +597,24 @@ where
     Ok(())
 }
 
+struct EscapeLinkTitle<'a>(&'a str);
+
+/// Writes a link title with double quotes escaped.
+/// See https://spec.commonmark.org/0.30/#link-title for the rules around
+/// link titles and the characters they may contain.
+impl fmt::Display for EscapeLinkTitle<'_> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        for c in self.0.chars() {
+            match c {
+                '"' => f.write_str(r#"\""#)?,
+                '\\' => f.write_str(r"\\")?,
+                c => f.write_char(c)?,
+            }
+        }
+        Ok(())
+    }
+}
+
 impl<'a> State<'a> {
     pub fn finalize<F>(mut self, mut formatter: F) -> Result<Self, fmt::Error>
     where

diff --git a/tests/fmt.rs b/tests/fmt.rs
@@ -872,6 +872,40 @@ mod escapes {
         );
     }
 
+    #[test]
+    fn link_titles() {
+        // See https://spec.commonmark.org/0.30/#link-title for the rules around
+        // link titles and the characters they may contain
+        assert_eq!(
+            fmts(r#"[link](http://example.com "'link title'")"#).0,
+            r#"[link](http://example.com "'link title'")"#
+        );
+        assert_eq!(
+            fmts(r#"[link](http://example.com "\\\"link \\ title\"")"#).0,
+            r#"[link](http://example.com "\\\"link \\ title\"")"#
+        );
+        assert_eq!(
+            fmts(r#"[link](http://example.com "\"link title\"")"#).0,
+            r#"[link](http://example.com "\"link title\"")"#
+        );
+        assert_eq!(
+            fmts(r#"[link](http://example.com '"link title"')"#).0,
+            r#"[link](http://example.com "\"link title\"")"#
+        );
+        assert_eq!(
+            fmts(r#"[link](http://example.com '\'link title\'')"#).0,
+            r#"[link](http://example.com "'link title'")"#
+        );
+        assert_eq!(
+            fmts(r#"[link](http://example.com (\(link title\)))"#).0,
+            r#"[link](http://example.com "(link title)")"#
+        );
+        assert_eq!(
+            fmts(r#"[link](http://example.com (你好👋))"#).0,
+            r#"[link](http://example.com "你好👋")"#
+        );
+    }
+
     #[test]
     fn it_does_esscape_lone_square_brackets_in_text() {
         assert_eq!(