Allow reference links with backticks (again)

docs/changelog.md

@@ -17,6 +17,8 @@ See the [Contributing Guide](contributing.md) for details.
 * Ensure nested elements inside inline comments are properly unescaped (#1571).
 * Make the docs build successfully with mkdocstrings-python 2.0 (#1575).
 * Fix infinite loop when multiple bogus or unclosed HTML comments appear in input (#1578).
+* Backtick formatting permitted in reference links to match conventional
+  links (#495).
 
 ## [3.10.0] - 2025-11-03
 

markdown/blockprocessors.py

@@ -580,16 +580,35 @@ class ReferenceProcessor(BlockProcessor):
         r'^[ ]{0,3}\[([^\[\]]*)\]:[ ]*\n?[ ]*([^\s]+)[ ]*(?:\n[ ]*)?((["\'])(.*)\4[ ]*|\((.*)\)[ ]*)?$', re.MULTILINE
     )
 
+    def __init__(self, parser: BlockParser):
+        super().__init__(parser)
+
+        from markdown.inlinepatterns import BACKTICK_RE, BacktickInlineProcessor
+        self.processor = BacktickInlineProcessor(BACKTICK_RE)
+
     def test(self, parent: etree.Element, block: str) -> bool:
         return True
 
     def run(self, parent: etree.Element, blocks: list[str]) -> bool:
         block = blocks.pop(0)
         m = self.RE.search(block)
         if m:
-            id = m.group(1).strip().lower()
+            id = m.group(1).strip()
             link = m.group(2).lstrip('<').rstrip('>')
             title = m.group(5) or m.group(6)
+
+            # ID may contain backticks that need to be processed, so process
+            # to the expanded form and use that as the id
+            bt_m = self.processor.compiled_re.search(id)
+            while bt_m and bt_m.group(3):
+                el, start, end = self.processor.handleMatch(bt_m, id)
+                id = '{}{}{}'.format(
+                    id[:start],
+                    etree.tostring(el, encoding='unicode'),
+                    id[end:]
+                )
+                bt_m = self.processor.compiled_re.search(id)
+
             self.parser.md.references[id] = (link, title)
             if block[m.end():].strip():
                 # Add any content after match back to blocks as separate block

markdown/inlinepatterns.py

@@ -892,6 +892,21 @@ def handleMatch(self, m: re.Match[str], data: str) -> tuple[etree.Element | None
         if not handled:
             return None, None, None
 
+        # If candidate data contains placeholder string - attempt to expand it
+        # in a limited way - only going 1 level deep.
+        if str(util.INLINE_PLACEHOLDER_PREFIX) in id:
+            inline_processor_index = self.md.treeprocessors.get_index_for_name('inline')
+
+            ex_m = util.INLINE_PLACEHOLDER_RE.search(id)
+            while ex_m and ex_m.group(1) in self.md.treeprocessors[inline_processor_index].stashed_nodes:
+                value = self.md.treeprocessors[inline_processor_index].stashed_nodes.get(ex_m.group(1))
+                if isinstance(value, str):
+                    id = id.replace(ex_m.group(0), value)
+                else:
+                    # An `etree` Element - return rendered version only
+                    id = id.replace(ex_m.group(0), ''.join(etree.tostring(value, encoding='unicode')))
+                ex_m = util.INLINE_PLACEHOLDER_RE.search(id)
+
         # Clean up line breaks in id
         id = self.NEWLINE_CLEANUP_RE.sub(' ', id)
         if id not in self.md.references:  # ignore undefined refs
@@ -911,10 +926,10 @@ def evalId(self, data: str, index: int, text: str) -> tuple[str | None, int, boo
         if not m:
             return None, index, False
         else:
-            id = m.group(1).lower()
+            id = m.group(1)
             end = m.end(0)
             if not id:
-                id = text.lower()
+                id = text
         return id, end, True
 
     def makeTag(self, href: str, title: str, text: str) -> etree.Element:
@@ -926,6 +941,7 @@ def makeTag(self, href: str, title: str, text: str) -> etree.Element:
             el.set('title', title)
 
         el.text = text
+
         return el
 
 
@@ -934,7 +950,7 @@ class ShortReferenceInlineProcessor(ReferenceInlineProcessor):
     def evalId(self, data: str, index: int, text: str) -> tuple[str, int, bool]:
         """Evaluate the id of `[ref]`.  """
 
-        return text.lower(), index, True
+        return text, index, True
 
 
 class ImageReferenceInlineProcessor(ReferenceInlineProcessor):

tests/test_syntax/inline/test_links.py

@@ -164,6 +164,29 @@ def test_angles_and_nonsense_url(self):
             '<p><a href="?}]*+|&amp;)">test nonsense</a>.</p>'
         )
 
+    def test_monospaced_title(self):
+        self.assertMarkdownRenders(
+            """[`test`](link)""",
+            """<p><a href="link"><code>test</code></a></p>"""
+        )
+
+    def test_title_containing_monospaced_title(self):
+        self.assertMarkdownRenders(
+            """[some `test`](link)""",
+            """<p><a href="link">some <code>test</code></a></p>"""
+        )
+
+        self.assertMarkdownRenders(
+            """before [`test` and `test`](link) after""",
+            """<p>before <a href="link"><code>test</code> and <code>test</code></a> after</p>"""
+        )
+
+    def test_title_containing_single_backtick(self):
+        self.assertMarkdownRenders(
+            """[some `test](link)""",
+            """<p><a href="link">some `test</a></p>"""
+        )
+
 
 class TestReferenceLinks(TestCase):
 
@@ -434,3 +457,74 @@ def test_ref_round_brackets(self):
                 """
             )
         )
+
+    def test_ref_link_monospaced_text(self):
+        self.assertMarkdownRenders(
+            self.dedent(
+                """
+                [`Text`]
+
+                [`Text`]: http://example.com
+                """
+            ),
+            """<p><a href="http://example.com"><code>Text</code></a></p>"""
+        )
+
+    def test_ref_link_with_containing_monospaced_text(self):
+
+        self.assertMarkdownRenders(
+            self.dedent(
+                """
+                text before [`Text` internal `Text`] text after
+
+                [`Text` internal `Text`]: http://example.com
+                """
+            ),
+            """<p>text before <a href="http://example.com"><code>Text</code> internal <code>Text</code></a> text after</p>"""
+        )
+
+        self.assertMarkdownRenders(
+            self.dedent(
+                """
+                [some `Text`]
+
+                [some `Text`]: http://example.com
+                """
+            ),
+            """<p><a href="http://example.com">some <code>Text</code></a></p>"""
+        )
+
+        self.assertMarkdownRenders(
+            self.dedent(
+                """
+                [`Text` after]
+
+                [`Text` after]: http://example.com
+                """
+            ),
+            """<p><a href="http://example.com"><code>Text</code> after</a></p>"""
+        )
+
+        self.assertMarkdownRenders(
+            self.dedent(
+                """
+                text before [`Text` internal] text after
+
+                [`Text` internal]: http://example.com
+                """
+            ),
+            """<p>text before <a href="http://example.com"><code>Text</code> internal</a> text after</p>"""
+        )
+
+
+    def test_ref_link_with_single_backtick(self):
+        self.assertMarkdownRenders(
+            self.dedent(
+                """
+                [some `Text]
+
+                [some `Text]: http://example.com
+                """
+            ),
+            """<p><a href="http://example.com">some `Text</a></p>"""
+        )