feat: Support footnotes that start on the next line.

src/mistune/plugins/footnotes.py

@@ -16,10 +16,10 @@
 _PARAGRAPH_SPLIT = re.compile(r"\n{2,}")
 # https://michelf.ca/projects/php-markdown/extra/#footnotes
 REF_FOOTNOTE = (
-    r"^(?P<footnote_lead> {0,3})"
-    r"\[\^(?P<footnote_key>" + LINK_LABEL + r")]:[ \t]"
+    r"^(?P<footnote_lead> {0,4})"
+    r"\[\^(?P<footnote_key>" + LINK_LABEL + r")]:[ \t\n]"
     r"(?P<footnote_text>[^\n]*(?:\n+|$)"
-    r"(?:(?P=footnote_lead) {1,3}(?! )[^\n]*\n+)*"
+    r"(?:(?P=footnote_lead) {1,4}(?! )[^\n]*\n+)*"
     r")"
 )
 
@@ -70,8 +70,11 @@ def parse_footnote_item(block: "BlockParser", key: str, index: int, state: Block
         spaces = len(second_line) - len(second_line.lstrip())
         pattern = re.compile(r"^ {" + str(spaces) + r",}", flags=re.M)
         text = pattern.sub("", text).strip()
-        items = _PARAGRAPH_SPLIT.split(text)
-        children = [{"type": "paragraph", "text": s} for s in items]
+
+        footer_state = BlockState()
+        footer_state.process(text)
+        block.parse(footer_state)
+        children = footer_state.tokens
     else:
         text = text.strip()
         children = [{"type": "paragraph", "text": text}]

tests/fixtures/footnotes.txt

@@ -31,15 +31,67 @@ multiple lines [^1]
    three
 
     four
+
+     five
 .
 <p>multiple lines <sup class="footnote-ref" id="fnref-1"><a href="#fn-1">1</a></sup></p>
-<pre><code>four</code></pre>
+<pre><code> five</code></pre>
 <section class="footnotes">
 <ol>
 <li id="fn-1"><p>foo</p>
 <p>one</p>
 <p>two</p>
-<p>three<a href="#fnref-1" class="footnote">&#8617;</a></p></li>
+<p>three</p>
+<p>four<a href="#fnref-1" class="footnote">&#8617;</a></p></li>
+</ol>
+</section>
+````````````````````````````````
+
+```````````````````````````````` example
+multi-line footnote[^1]
+
+[^1]:
+    Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod
+    tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam,
+    quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo
+    consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse
+    cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat
+    non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.
+.
+<p>multi-line footnote<sup class="footnote-ref" id="fnref-1"><a href="#fn-1">1</a></sup></p>
+<section class="footnotes">
+<ol>
+<li id="fn-1"><p>Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod
+tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam,
+quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo
+consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse
+cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat
+non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.<a href="#fnref-1" class="footnote">&#8617;</a></p></li>
+</ol>
+</section>
+````````````````````````````````
+
+```````````````````````````````` example
+fenced code block in footnote[^1]
+
+[^1]:
+    first
+
+    ```sh
+    second
+    third
+    ```
+
+    fourth
+.
+<p>fenced code block in footnote<sup class="footnote-ref" id="fnref-1"><a href="#fn-1">1</a></sup></p>
+<section class="footnotes">
+<ol>
+<li id="fn-1"><p>first</p>
+<pre><code class="language-sh">second
+third
+</code></pre>
+<p>fourth<a href="#fnref-1" class="footnote">&#8617;</a></p></li>
 </ol>
 </section>
 ````````````````````````````````