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Replace an instance of IO with a protocol #5471

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Merged
merged 3 commits into from
May 19, 2021
Merged

Replace an instance of IO with a protocol #5471

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53ad1a3
Replace an instance of IO with a protocol
srittau May 16, 2021
3447d14
Use bool instead of Literal[False]
srittau May 16, 2021
6101f59
Use 'object' over 'Any' for protocol returns
srittau May 16, 2021
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57 changes: 54 additions & 3 deletions stdlib/zipfile.pyi
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Original file line number Diff line number Diff line change
Expand Up @@ -2,7 +2,8 @@ import io
import sys
from _typeshed import StrPath
from types import TracebackType
from typing import IO, Any, Callable, Dict, Iterable, Iterator, List, Optional, Protocol, Sequence, Tuple, Type, Union
from typing import IO, Any, Callable, Dict, Iterable, Iterator, List, Optional, Protocol, Sequence, Tuple, Type, Union, overload
from typing_extensions import Literal

_DateTuple = Tuple[int, int, int, int, int, int]

Expand All @@ -13,6 +14,16 @@ error = BadZipfile

class LargeZipFile(Exception): ...

class _ZipStream(Protocol):
def read(self, __n: int) -> bytes: ...
# The following methods are optional:
# def seekable(self) -> bool: ...
# def tell(self) -> int: ...
# def seek(self, __n: int) -> Any: ...

class _ClosableZipStream(_ZipStream, Protocol):
def close(self) -> Any: ...

class ZipExtFile(io.BufferedIOBase):
MAX_N: int = ...
MIN_READ_SIZE: int = ...
Expand All @@ -24,13 +35,53 @@ class ZipExtFile(io.BufferedIOBase):
mode: str
name: str
if sys.version_info >= (3, 7):
@overload
def __init__(
self, fileobj: _ClosableZipStream, mode: str, zipinfo: ZipInfo, pwd: Optional[bytes], close_fileobj: Literal[True]
) -> None: ...
@overload
def __init__(
self, fileobj: IO[bytes], mode: str, zipinfo: ZipInfo, pwd: Optional[bytes] = ..., close_fileobj: bool = ...
self,
fileobj: _ClosableZipStream,
mode: str,
zipinfo: ZipInfo,
pwd: Optional[bytes] = ...,
*,
close_fileobj: Literal[True],
) -> None: ...
@overload
def __init__(
self,
fileobj: _ZipStream,
mode: str,
zipinfo: ZipInfo,
pwd: Optional[bytes] = ...,
close_fileobj: bool = ...,
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I don't think this works as intended. If fileobj is a _ZipStream but not a _ClosableZipStream, and you pass close_fileobj=True, it will match this overload instead of erroring.

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See above: I think this is a reasonable tradeoff, considering our "prefer false negatives over false positives" policy.

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Then we might as well get rid of _ClosableZipStream altogether, because distinguishing between closable and non-closable zip streams doesn't affect whether the code type-checks.

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But having it separate has the advantage that the following fails:

ZipExtFile(my_non_closable_stream, close_fileobj=True)

The only thing that can't be checked properly is the following:

close: bool = True
ZipExtFile(my_non_closable_stream, close_fileobj=close)

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@Akuli Akuli May 16, 2021 •
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I don't think that fails. It doesn't match the first two overloads, but it does match the third overload which just requires any stream, and bool for close_fileobj. (Note that True converts to bool.)

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Good point. At this point I think that maybe the first solution was the best, and until python/mypy#6113 is fixed, people just use # type: ignore?

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Since we prefer false negatives, it might be better to just never require a .close() method.

) -> None: ...
else:
@overload
def __init__(
self,
fileobj: _ClosableZipStream,
mode: str,
zipinfo: ZipInfo,
decrypter: Optional[Callable[[Sequence[int]], bytes]],
close_fileobj: Literal[True],
) -> None: ...
@overload
def __init__(
self,
fileobj: _ClosableZipStream,
mode: str,
zipinfo: ZipInfo,
decrypter: Optional[Callable[[Sequence[int]], bytes]] = ...,
*,
close_fileobj: Literal[True],
) -> None: ...
@overload
def __init__(
self,
fileobj: IO[bytes],
fileobj: _ZipStream,
mode: str,
zipinfo: ZipInfo,
decrypter: Optional[Callable[[Sequence[int]], bytes]] = ...,
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