_utils.py

import os
import sys
import warnings
import functools

from typing import Any, Dict

# Avoid "LookupError: unknown encoding: ascii" when open() called in a destructor
outnull_file = open(os.devnull, "w")
errnull_file = open(os.devnull, "w")

STDOUT_FILENO = 1
STDERR_FILENO = 2


class suppress_stdout_stderr(object):
    # NOTE: these must be "saved" here to avoid exceptions when using
    #       this context manager inside of a __del__ method
    sys = sys
    os = os

    def __init__(self, disable: bool = True):
        self.disable = disable

    # Oddly enough this works better than the contextlib version
    def __enter__(self):
        if self.disable:
            return self

        self.old_stdout_fileno_undup = STDOUT_FILENO
        self.old_stderr_fileno_undup = STDERR_FILENO

        self.old_stdout_fileno = self.os.dup(self.old_stdout_fileno_undup)
        self.old_stderr_fileno = self.os.dup(self.old_stderr_fileno_undup)

        self.old_stdout = self.sys.stdout
        self.old_stderr = self.sys.stderr

        self.os.dup2(outnull_file.fileno(), self.old_stdout_fileno_undup)
        self.os.dup2(errnull_file.fileno(), self.old_stderr_fileno_undup)

        self.sys.stdout = outnull_file
        self.sys.stderr = errnull_file
        return self

    def __exit__(self, *_):
        if self.disable:
            return

        # Check if sys.stdout and sys.stderr have fileno method
        self.sys.stdout = self.old_stdout
        self.sys.stderr = self.old_stderr

        self.os.dup2(self.old_stdout_fileno, self.old_stdout_fileno_undup)
        self.os.dup2(self.old_stderr_fileno, self.old_stderr_fileno_undup)

        self.os.close(self.old_stdout_fileno)
        self.os.close(self.old_stderr_fileno)


class MetaSingleton(type):
    """
    Metaclass for implementing the Singleton pattern.
    """

    _instances: Dict[type, Any] = {}

    def __call__(cls, *args: Any, **kwargs: Any) -> Any:
        if cls not in cls._instances:
            cls._instances[cls] = super(MetaSingleton, cls).__call__(*args, **kwargs)
        return cls._instances[cls]


class Singleton(object, metaclass=MetaSingleton):
    """
    Base class for implementing the Singleton pattern.
    """

    def __init__(self):
        super(Singleton, self).__init__()


def deprecated(reason):
    def decorator(func):
        @functools.wraps(func)
        def wrapper(*args, **kwargs):
            warnings.warn(
                f"Call to deprecated function {func.__name__} ({reason}).",
                category=DeprecationWarning,
                stacklevel=2,
            )
            return func(*args, **kwargs)
        return wrapper
    return decorator