from contextvars import ContextVar
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from typing import Optional
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import sys
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import threading
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current_async_library_cvar = ContextVar(
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"current_async_library_cvar", default=None
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) # type: ContextVar[Optional[str]]
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|
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class _ThreadLocal(threading.local):
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# Since threading.local provides no explicit mechanism is for setting
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# a default for a value, a custom class with a class attribute is used
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# instead.
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name = None # type: Optional[str]
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|
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thread_local = _ThreadLocal()
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class AsyncLibraryNotFoundError(RuntimeError):
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pass
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def current_async_library() -> str:
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"""Detect which async library is currently running.
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The following libraries are currently supported:
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================ =========== ============================
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Library Requires Magic string
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================ =========== ============================
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**Trio** Trio v0.6+ ``"trio"``
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**Curio** - ``"curio"``
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**asyncio** ``"asyncio"``
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**Trio-asyncio** v0.8.2+ ``"trio"`` or ``"asyncio"``,
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depending on current mode
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================ =========== ============================
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Returns:
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A string like ``"trio"``.
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Raises:
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AsyncLibraryNotFoundError: if called from synchronous context,
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or if the current async library was not recognized.
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Examples:
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.. code-block:: python3
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from sniffio import current_async_library
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async def generic_sleep(seconds):
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library = current_async_library()
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if library == "trio":
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import trio
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await trio.sleep(seconds)
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elif library == "asyncio":
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import asyncio
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await asyncio.sleep(seconds)
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# ... and so on ...
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else:
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raise RuntimeError(f"Unsupported library {library!r}")
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"""
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value = thread_local.name
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if value is not None:
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return value
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value = current_async_library_cvar.get()
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if value is not None:
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return value
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# Need to sniff for asyncio
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if "asyncio" in sys.modules:
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import asyncio
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try:
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current_task = asyncio.current_task # type: ignore[attr-defined]
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except AttributeError:
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current_task = asyncio.Task.current_task # type: ignore[attr-defined]
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try:
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if current_task() is not None:
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return "asyncio"
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except RuntimeError:
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pass
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# Sniff for curio (for now)
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if 'curio' in sys.modules:
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from curio.meta import curio_running
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if curio_running():
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return 'curio'
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raise AsyncLibraryNotFoundError(
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"unknown async library, or not in async context"
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)
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