Add support for reStructuredText literal blocks (#196)

Co-authored-by: Adam Johnson <me@adamj.eu>
fix #195

HISTORY.rst

@@ -4,6 +4,9 @@ History
 
 * Require Black 22.1.0+.
 
+* Add ``--rst-literal-blocks`` option, to also format text in reStructuredText literal blocks, starting with ``::``.
+  Sphinx highlights these with the project’s default language, which defaults to Python.
+
 1.12.1 (2022-01-30)
 -------------------
 

README.md

@@ -29,6 +29,7 @@ options:
 Following additional parameters can be used:
 
  - `-E` / `--skip-errors`
+ - `--rst-literal-blocks`
 
 `blacken-docs` will format code in the following block types:
 
@@ -59,6 +60,8 @@ Following additional parameters can be used:
             print("hello world")
 ```
 
+This style is enabled with the `--use-sphinx-default` option.
+
 (rst `pycon`)
 ```rst
     .. code-block:: pycon
@@ -68,6 +71,19 @@ Following additional parameters can be used:
         ...
 ```
 
+(rst literal blocks - activated with ``--rst-literal-blocks``)
+
+reStructuredText [literal blocks](https://docutils.sourceforge.io/docs/ref/rst/restructuredtext.html#literal-blocks) are marked with `::` and can be any monospaced text by default.
+However Sphinx interprets them as Python code [by default](https://www.sphinx-doc.org/en/master/usage/restructuredtext/basics.html#rst-literal-blocks).
+If your project uses Sphinx and such a configuration, add `--rst-literal-blocks` to also format such blocks.
+
+``rst
+    An example::
+
+        def hello():
+            print("hello world")
+```
+
 (latex)
 ```latex
 \begin{minted}{python}

src/blacken_docs/__init__.py

@@ -42,6 +42,15 @@
     rf'(?P<code>(^((?P=indent) +.*)?\n)+)',
     re.MULTILINE,
 )
+RST_LITERAL_BLOCKS_RE = re.compile(
+    r'(?P<before>'
+    r'^(?! *\.\. )(?P<indent> *).*::\n'
+    r'((?P=indent) +:.*\n)*'
+    r'\n*'
+    r')'
+    r'(?P<code>(^((?P=indent) +.*)?\n)+)',
+    re.MULTILINE,
+)
 RST_PYCON_RE = re.compile(
     r'(?P<before>'
     r'(?P<indent> *)\.\. ((code|code-block):: pycon|doctest::.*)\n'
@@ -85,7 +94,10 @@ class CodeBlockError(NamedTuple):
 
 
 def format_str(
-        src: str, black_mode: black.FileMode,
+        src: str,
+        black_mode: black.FileMode,
+        *,
+        rst_literal_blocks: bool = False,
 ) -> tuple[str, Sequence[CodeBlockError]]:
     errors: list[CodeBlockError] = []
 
@@ -117,6 +129,19 @@ def _rst_match(match: Match[str]) -> str:
         code = textwrap.indent(code, min_indent)
         return f'{match["before"]}{code.rstrip()}{trailing_ws}'
 
+    def _rst_literal_blocks_match(match: Match[str]) -> str:
+        if not match['code'].strip():
+            return match[0]
+        min_indent = min(INDENT_RE.findall(match['code']))
+        trailing_ws_match = TRAILING_NL_RE.search(match['code'])
+        assert trailing_ws_match
+        trailing_ws = trailing_ws_match.group()
+        code = textwrap.dedent(match['code'])
+        with _collect_error(match):
+            code = black.format_str(code, mode=black_mode)
+        code = textwrap.indent(code, min_indent)
+        return f'{match["before"]}{code.rstrip()}{trailing_ws}'
+
     def _pycon_match(match: Match[str]) -> str:
         code = ''
         fragment: str | None = None
@@ -189,18 +214,30 @@ def _latex_pycon_match(match: Match[str]) -> str:
     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)
+    if rst_literal_blocks:
+        src = RST_LITERAL_BLOCKS_RE.sub(
+            _rst_literal_blocks_match,
+            src,
+        )
     src = LATEX_RE.sub(_latex_match, src)
     src = LATEX_PYCON_RE.sub(_latex_pycon_match, src)
     src = PYTHONTEX_RE.sub(_latex_match, src)
     return src, errors
 
 
 def format_file(
-        filename: str, black_mode: black.FileMode, skip_errors: bool,
+        filename: str,
+        black_mode: black.FileMode,
+        skip_errors: bool,
+        rst_literal_blocks: bool,
 ) -> int:
     with open(filename, encoding='UTF-8') as f:
         contents = f.read()
-    new_contents, errors = format_str(contents, black_mode)
+    new_contents, errors = format_str(
+        contents,
+        black_mode,
+        rst_literal_blocks=rst_literal_blocks,
+    )
     for error in errors:
         lineno = contents[:error.offset].count('\n') + 1
         print(f'{filename}:{lineno}: code block parse error {error.exc}')
@@ -233,6 +270,9 @@ def main(argv: Sequence[str] | None = None) -> int:
         '-S', '--skip-string-normalization', action='store_true',
     )
     parser.add_argument('-E', '--skip-errors', action='store_true')
+    parser.add_argument(
+        '--rst-literal-blocks', action='store_true',
+    )
     parser.add_argument('filenames', nargs='*')
     args = parser.parse_args(argv)
 
@@ -244,5 +284,10 @@ def main(argv: Sequence[str] | None = None) -> int:
 
     retv = 0
     for filename in args.filenames:
-        retv |= format_file(filename, black_mode, skip_errors=args.skip_errors)
+        retv |= format_file(
+            filename,
+            black_mode,
+            skip_errors=args.skip_errors,
+            rst_literal_blocks=args.rst_literal_blocks,
+        )
     return retv

tests/blacken_docs_test.py

@@ -1,5 +1,7 @@
 from __future__ import annotations
 
+from textwrap import dedent
+
 import black
 from black.const import DEFAULT_LINE_LENGTH
 
@@ -197,6 +199,60 @@ def test_format_src_rst():
     )
 
 
+def test_format_src_rst_literal_blocks():
+    before = (
+        'hello::\n'
+        '\n'
+        '    f(1,2,3)\n'
+        '\n'
+        'world\n'
+    )
+    after, _ = blacken_docs.format_str(
+        before, BLACK_MODE, rst_literal_blocks=True,
+    )
+    assert after == (
+        'hello::\n'
+        '\n'
+        '    f(1, 2, 3)\n'
+        '\n'
+        'world\n'
+    )
+
+
+def test_format_src_rst_literal_blocks_nested():
+    before = dedent(
+        '''
+        * hello
+
+          .. warning::
+
+            don't hello too much
+        ''',
+    )
+    after, errors = blacken_docs.format_str(
+        before, BLACK_MODE, rst_literal_blocks=True,
+    )
+    assert after == before
+    assert errors == []
+
+
+def test_format_src_rst_literal_blocks_empty():
+    before = dedent(
+        '''
+        Example::
+
+        .. warning::
+
+            There was no example.
+        ''',
+    )
+    after, errors = blacken_docs.format_str(
+        before, BLACK_MODE, rst_literal_blocks=True,
+    )
+    assert after == before
+    assert errors == []
+
+
 def test_format_src_rst_sphinx_doctest():
     before = (
         '.. testsetup:: group1\n'