"""Defines any IO utilities used by isort"""
import dataclasses
import re
import tokenize
from contextlib import contextmanager
from io import BytesIO, StringIO, TextIOWrapper
from pathlib import Path
from typing import Any, Callable, Iterator, TextIO, Union
from isort.exceptions import UnsupportedEncoding
_ENCODING_PATTERN = re.compile(rb"^[ \t\f]*#.*?coding[:=][ \t]*([-_.a-zA-Z0-9]+)")
@dataclasses.dataclass(frozen=True)
class File:
stream: TextIO
path: Path
encoding: str
@staticmethod
def detect_encoding(filename: Union[str, Path], readline: Callable[[], bytes]) -> str:
try:
return tokenize.detect_encoding(readline)[0]
except Exception:
raise UnsupportedEncoding(filename)
@staticmethod
def from_contents(contents: str, filename: str) -> "File":
encoding = File.detect_encoding(filename, BytesIO(contents.encode("utf-8")).readline)
return File(stream=StringIO(contents), path=Path(filename).resolve(), encoding=encoding)
@property
def extension(self) -> str:
return self.path.suffix.lstrip(".")
@staticmethod
def _open(filename: Union[str, Path]) -> TextIOWrapper:
"""Open a file in read only mode using the encoding detected by
detect_encoding().
"""
buffer = open(filename, "rb")
try:
encoding = File.detect_encoding(filename, buffer.readline)
buffer.seek(0)
text = TextIOWrapper(buffer, encoding, line_buffering=True, newline="")
text.mode = "r" # type: ignore
return text
except Exception:
buffer.close()
raise
@staticmethod
@contextmanager
def read(filename: Union[str, Path]) -> Iterator["File"]:
file_path = Path(filename).resolve()
stream = None
try:
stream = File._open(file_path)
yield File(stream=stream, path=file_path, encoding=stream.encoding)
finally:
if stream is not None:
stream.close()
class _EmptyIO(StringIO):
def write(self, *args: Any, **kwargs: Any) -> None: # type: ignore # skipcq: PTC-W0049
pass
Empty = _EmptyIO()
