def _format_str_once(src_contents: str, *, mode: Mode) -> str:
src_node = lib2to3_parse(src_contents.lstrip(), mode.target_versions)
dst_contents = []
future_imports = get_future_imports(src_node)
if mode.target_versions:
versions = mode.target_versions
else:
versions = detect_target_versions(src_node,
future_imports=future_imports)
normalize_fmt_off(src_node, preview=mode.preview)
lines = LineGenerator(mode=mode)
elt = EmptyLineTracker(is_pyi=mode.is_pyi)
empty_line = Line(mode=mode)
after = 0
split_line_features = {
feature
for feature in
{Feature.TRAILING_COMMA_IN_CALL, Feature.TRAILING_COMMA_IN_DEF}
if supports_feature(versions, feature)
}
for current_line in lines.visit(src_node):
dst_contents.append(str(empty_line) * after)
before, after = elt.maybe_empty_lines(current_line)
dst_contents.append(str(empty_line) * before)
for line in transform_line(current_line,
mode=mode,
features=split_line_features):
dst_contents.append(str(line))
return "".join(dst_contents)
def get_grammars(target_versions: Set[TargetVersion]) -> List[Grammar]:
if not target_versions:
# No target_version specified, so try all grammars.
return [
# Python 3.7+
pygram.
python_grammar_no_print_statement_no_exec_statement_async_keywords,
# Python 3.0-3.6
pygram.python_grammar_no_print_statement_no_exec_statement,
# Python 2.7 with future print_function import
pygram.python_grammar_no_print_statement,
# Python 2.7
pygram.python_grammar,
]
if all(version.is_python2() for version in target_versions):
# Python 2-only code, so try Python 2 grammars.
return [
# Python 2.7 with future print_function import
pygram.python_grammar_no_print_statement,
# Python 2.7
pygram.python_grammar,
]
# Python 3-compatible code, so only try Python 3 grammar.
grammars = []
if supports_feature(target_versions, Feature.PATTERN_MATCHING):
# Python 3.10+
grammars.append(pygram.python_grammar_soft_keywords)
# If we have to parse both, try to parse async as a keyword first
if not supports_feature(
target_versions,
Feature.ASYNC_IDENTIFIERS) and not supports_feature(
target_versions, Feature.PATTERN_MATCHING):
# Python 3.7-3.9
grammars.append(
pygram.
python_grammar_no_print_statement_no_exec_statement_async_keywords)
if not supports_feature(target_versions, Feature.ASYNC_KEYWORDS):
# Python 3.0-3.6
grammars.append(
pygram.python_grammar_no_print_statement_no_exec_statement)
# At least one of the above branches must have been taken, because every Python
# version has exactly one of the two 'ASYNC_*' flags
return grammars
def format_str(src_contents: str, *, mode: Mode) -> FileContent:
"""Reformat a string and return new contents.
`mode` determines formatting options, such as how many characters per line are
allowed. Example:
>>> import black
>>> print(black.format_str("def f(arg:str='')->None:...", mode=black.Mode()))
def f(arg: str = "") -> None:
...
A more complex example:
>>> print(
... black.format_str(
... "def f(arg:str='')->None: hey",
... mode=black.Mode(
... target_versions={black.TargetVersion.PY36},
... line_length=10,
... string_normalization=False,
... is_pyi=False,
... ),
... ),
... )
def f(
arg: str = '',
) -> None:
hey
"""
src_node = lib2to3_parse(src_contents.lstrip(), mode.target_versions)
dst_contents = []
future_imports = get_future_imports(src_node)
if mode.target_versions:
versions = mode.target_versions
else:
versions = detect_target_versions(src_node)
# TODO: fully drop support and this code hopefully in January 2022 :D
if TargetVersion.PY27 in mode.target_versions or versions == {
TargetVersion.PY27
}:
msg = (
"DEPRECATION: Python 2 support will be removed in the first stable release "
"expected in January 2022.")
err(msg, fg="yellow", bold=True)
normalize_fmt_off(src_node)
lines = LineGenerator(
mode=mode,
remove_u_prefix="unicode_literals" in future_imports
or supports_feature(versions, Feature.UNICODE_LITERALS),
)
elt = EmptyLineTracker(is_pyi=mode.is_pyi)
empty_line = Line(mode=mode)
after = 0
split_line_features = {
feature
for feature in
{Feature.TRAILING_COMMA_IN_CALL, Feature.TRAILING_COMMA_IN_DEF}
if supports_feature(versions, feature)
}
for current_line in lines.visit(src_node):
dst_contents.append(str(empty_line) * after)
before, after = elt.maybe_empty_lines(current_line)
dst_contents.append(str(empty_line) * before)
for line in transform_line(current_line,
mode=mode,
features=split_line_features):
dst_contents.append(str(line))
return "".join(dst_contents)