fix: two backticks with no closing run trip up link parser (#663) (#665)

Signed-off-by: squidfunk <martin.donath@squidfunk.com>

python/tests/unit/collectors/test_references.py

@@ -1554,6 +1554,10 @@ class TestInlineCode:
                 b"``text`[text](href)``",
                 id="inline-code, inner backticks",
             ),
+            pytest.param(
+                b"`` `[text](href)`",
+                id="inline-code, empty code span",
+            ),
         ],
     )
     def test_inline_code(self, md: bytes) -> None:

python/zensical/collectors/references/cursor.py

@@ -198,12 +198,25 @@ def _scan(cursor: Cursor) -> Iterator[Reference]:
 
         # Code block: ```...``` or `...`
         if char == _BACKTICK:
-            if cursor.at_line_start():
+            # Consume the full run so a failed match does not leave trailing
+            # backticks to be rescanned as new delimiters.
+            count = 1
+            while cursor.peek(count) == _BACKTICK:
+                count += 1
+            if (
+                cursor.at_line_start()
+                and count >= 3  # noqa: PLR2004
+                and cursor.peek(count) in (_SPACE, _TAB, _NL, _CR, -1)
+            ):
                 end = _scan_fenced_code(cursor, _BACKTICK)
                 if end is not None:
                     cursor.advance(end - cursor.pos)
                     continue
 
+                # Literal
+                cursor.advance(count)
+                continue
+
             # Inline code: `...`
             end = _scan_inline_code(cursor)
             if end is not None:
@@ -211,7 +224,7 @@ def _scan(cursor: Cursor) -> Iterator[Reference]:
                 continue
 
             # Literal
-            cursor.advance(1)
+            cursor.advance(count)
             continue
 
         # Code block: ~~~...~~~