ruff/crates/ty_python_semantic/resources/mdtest/call/open.md

Calls to open()

builtins.open

We do not fully understand typeshed's overloads for open() yet, due to missing support for PEP-613 type aliases. However, we also do not emit false-positive diagnostics on common calls to open():

import pickle

reveal_type(open(""))  # revealed: TextIOWrapper[_WrappedBuffer]
reveal_type(open("", "r"))  # revealed: TextIOWrapper[_WrappedBuffer]
reveal_type(open("", "rb"))  # revealed: BufferedReader[_BufferedReaderStream]

with open("foo.pickle", "rb") as f:
    x = pickle.load(f)  # fine

def _(mode: str):
    reveal_type(open("", mode))  # revealed: IO[Any]

os.fdopen

The same is true for os.fdopen():

import pickle
import os

reveal_type(os.fdopen(0))  # revealed: TextIOWrapper[_WrappedBuffer]
reveal_type(os.fdopen(0, "r"))  # revealed: TextIOWrapper[_WrappedBuffer]
reveal_type(os.fdopen(0, "rb"))  # revealed: BufferedReader[_BufferedReaderStream]

with os.fdopen(0, "rb") as f:
    x = pickle.load(f)  # fine

Path.open

And similarly for Path.open():

from pathlib import Path
import pickle

reveal_type(Path("").open())  # revealed: TextIOWrapper[_WrappedBuffer]
reveal_type(Path("").open("r"))  # revealed: TextIOWrapper[_WrappedBuffer]
reveal_type(Path("").open("rb"))  # revealed: BufferedReader[_BufferedReaderStream]

with Path("foo.pickle").open("rb") as f:
    x = pickle.load(f)  # fine

NamedTemporaryFile

And similarly for tempfile.NamedTemporaryFile():

from tempfile import NamedTemporaryFile
import pickle

reveal_type(NamedTemporaryFile())  # revealed: _TemporaryFileWrapper[bytes]
reveal_type(NamedTemporaryFile("r"))  # revealed: _TemporaryFileWrapper[str]
reveal_type(NamedTemporaryFile("rb"))  # revealed: _TemporaryFileWrapper[bytes]

with NamedTemporaryFile("rb") as f:
    x = pickle.load(f)  # fine