Add support for Python Markdown SuperFences

src/blacken_docs/__init__.py

@@ -23,6 +23,17 @@
     r"(?P<after>^(?P=indent)```[^\S\r\n]*$)",
     re.DOTALL | re.MULTILINE,
 )
+PYGMENTS_PY_LANG_CLASSES_RE_FRAGMENT = (
+    "(" + "|".join([r"\." + lang for lang in PYGMENTS_PY_LANGS]) + ")"
+)
+MD_BRACE_RE = re.compile(
+    r"(?P<before>^(?P<indent> *)```\s*\{\s*"
+    + PYGMENTS_PY_LANG_CLASSES_RE_FRAGMENT
+    + r"( [^\}\n]*?)?\}\s*?\n)"
+    r"(?P<code>.*?)"
+    r"(?P<after>^(?P=indent)```\s*$)",
+    re.DOTALL | re.MULTILINE,
+)
 MD_PYCON_RE = re.compile(
     r"(?P<before>^(?P<indent> *)```[^\S\r\n]*pycon( .*?)?\n)"
     r"(?P<code>.*?)"
@@ -265,6 +276,7 @@ def _latex_pycon_match(match: Match[str]) -> str:
         return f'{match["before"]}{code}{match["after"]}'
 
     src = MD_RE.sub(_md_match, src)
+    src = MD_BRACE_RE.sub(_md_match, src)
     src = MD_PYCON_RE.sub(_md_pycon_match, src)
     src = RST_RE.sub(_rst_match, src)
     src = RST_PYCON_RE.sub(_rst_pycon_match, src)

tests/test_blacken_docs.py

@@ -102,6 +102,24 @@ def test_format_src_markdown_options():
     )
 
 
+def test_format_src_markdown_braces():
+    before = dedent(
+        """\
+        ```{.python title='example.py'}
+        f(1,2,3)
+        ```
+        """
+    )
+    after, _ = blacken_docs.format_str(before, BLACK_MODE)
+    assert after == dedent(
+        """\
+        ```{.python title='example.py'}
+        f(1, 2, 3)
+        ```
+        """
+    )
+
+
 def test_format_src_markdown_trailing_whitespace():
     before = dedent(
         """\