feat: add autorestore_context option and make it True by default

[spumer]

The main reason for this behavior is we make usage of async_to_sync and sync_to_async is transparent.
Programmers can use it without any unexpected side effects.

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So, i can wait for your PR #19 and adapt my changes.

We use your lib on production since 2023 and i wrote article about that:
https://habr.com/ru/companies/tochka/articles/798577/

We run sync handlers in fastapi through asyncio-gevent, and this save us! Thank you for this project!

Summary by Sourcery

Add context preservation functionality to async and sync function conversions in asyncio-gevent

New Features:

• Introduce an autorestore_context option that preserves context variables when converting between sync and async functions
• Add support for passing and restoring context variables across greenlet and future conversions

Enhancements:

• Modify async_to_sync, sync_to_async, and greenlet_to_future functions to support context variable preservation
• Improve context handling to make async and sync function conversions more transparent

Tests:

• Add test cases to verify context preservation for both sync_to_async and async_to_sync function conversions

[cr-gpt]

Seems you are using me but didn't get OPENAI_API_KEY seted in Variables/Secrets for this repo. you could follow readme for more information

[sourcery-ai]

Reviewer's Guide by Sourcery

This pull request introduces an autorestore_context option to greenlet_to_future, async_to_sync, and sync_to_async functions. This option, enabled by default, ensures that context variables are properly passed and restored when switching between asyncio and gevent, providing more transparent usage of async_to_sync and sync_to_async.

Sequence diagram for sync_to_async with autorestore_context

sequenceDiagram
    participant SyncFn as Synchronous Function
    participant geventGreenlet as gevent.Greenlet
    participant greenlet_to_future as greenlet_to_future
    participant asyncioEventLoop as asyncio Event Loop
    participant Future as asyncio.Future

    SyncFn->>geventGreenlet: gevent.Greenlet(fn, *args, **kwargs)
    activate geventGreenlet
    geventGreenlet->>greenlet_to_future: greenlet_to_future(greenlet, autorestore_context=True)
    activate greenlet_to_future
    greenlet_to_future->>asyncioEventLoop: loop.run_in_executor(fn)
    activate asyncioEventLoop
    asyncioEventLoop-->>greenlet_to_future: Result from fn
    deactivate asyncioEventLoop
    greenlet_to_future->>Future: Resolves with result
    deactivate greenlet_to_future
    Future-->>geventGreenlet: Result
    geventGreenlet-->>SyncFn: Result
    deactivate geventGreenlet

    opt autorestore_context is True
        geventGreenlet->>SyncFn: Restore context variables
    end

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Sequence diagram for async_to_sync with autorestore_context

sequenceDiagram
    participant AsyncCoroutine as Asynchronous Coroutine
    participant future_to_greenlet as future_to_greenlet
    participant geventGreenlet as gevent.Greenlet
    participant asyncioEventLoop as asyncio Event Loop
    participant Future as asyncio.Future

    AsyncCoroutine->>future_to_greenlet: future_to_greenlet(coroutine(), autorestore_context=True)
    activate future_to_greenlet
    future_to_greenlet->>asyncioEventLoop: loop.create_task(coroutine())
    activate asyncioEventLoop
    asyncioEventLoop-->>future_to_greenlet: Future
    deactivate asyncioEventLoop
    future_to_greenlet->>geventGreenlet: gevent.Greenlet(run_until_complete, future)
    activate geventGreenlet
    geventGreenlet->>Future: Await Future
    Future-->>geventGreenlet: Result
    deactivate geventGreenlet
    future_to_greenlet-->>AsyncCoroutine: Result
    deactivate future_to_greenlet

    opt autorestore_context is True
        geventGreenlet->>AsyncCoroutine: Restore context variables
    end

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File-Level Changes

Change	Details	Files
Introduces an autorestore_context option to greenlet_to_future, async_to_sync, and sync_to_async functions, enabled by default, to automatically pass and restore context variables when switching between asyncio and gevent.	Added autorestore_context parameter to greenlet_to_future, async_to_sync, and sync_to_async functions. Modified greenlet_to_future to copy the context and restore it after execution. Modified async_to_sync to copy the context and restore it after execution. Modified sync_to_async to copy the context and restore it after execution. Added tests to verify context passing and restoration for async_to_sync and sync_to_async.	tests/test_asyncio_on_gevent.py asyncio_gevent/greenlet_to_future.py asyncio_gevent/future_to_greenlet.py asyncio_gevent/async_to_sync.py asyncio_gevent/sync_to_async.py

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[sourcery-ai]

Hey @spumer - I've reviewed your changes - here's some feedback:

Overall Comments:

• Consider adding a helper function to avoid repeating the context restoration logic in async_to_sync and greenlet_to_future.
• The added tests are great for demonstrating the context preservation, but consider adding tests that verify context isolation between greenlets.

Here's what I looked at during the review

• 🟡 General issues: 4 issues found
• 🟢 Security: all looks good
• 🟢 Testing: all looks good
• 🟢 Complexity: all looks good
• 🟢 Documentation: all looks good

---

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[spumer]

@gfmio can you review too?)

[Copilot]

Pull Request Overview

This PR adds an autorestore_context option (enabled by default) to preserve context variables when converting between sync and async functions, making async_to_sync, sync_to_async, and related internals context‐aware and transparent.

• Introduce autorestore_context parameter in sync_to_async and async_to_sync and propagate it to greenlet_to_future
• Capture, pass, and restore contextvars in _await_greenlet and future_to_greenlet
• Add tests to verify context preservation across greenlet/future boundaries

Reviewed Changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
tests/test_asyncio_on_gevent.py	Add tests for context preservation in sync_to_async and async_to_sync
asyncio_gevent/sync_to_async.py	Added autorestore_context parameter and forwarded it to greenlet_to_future
asyncio_gevent/greenlet_to_future.py	Capture contextvars before start, restore after await, updated signature and executor
asyncio_gevent/future_to_greenlet.py	Propagate gr_context when scheduling coroutine futures
asyncio_gevent/async_to_sync.py	Added autorestore_context parameter and restore context after sync call

Comments suppressed due to low confidence (3)

asyncio_gevent/greenlet_to_future.py:82

• The return type of greenlet_to_future was changed from asyncio.Future to typing.Awaitable, which may be a breaking API change. Consider documenting this change or providing backward compatibility.

) -> typing.Awaitable:

tests/test_asyncio_on_gevent.py:97

• [nitpick] Test function name is verbose and uses multiple underscores; consider renaming to test_sync_to_async_context_preservation for clarity.

def test_asyncio_on_gevent___sync_to_async__pass_and_copyback_context():

tests/test_asyncio_on_gevent.py:1

• The tests reference asyncio_gevent but there is no import asyncio_gevent statement. Add import asyncio_gevent at the top to avoid NameError.

import contextvars

[gfmio]

Thank you for using asyncio-gevent, I'm glad you find it useful! Thank you also for your PR and sorry for the wait.

I've just had a quick look and I think the PR looks good to me (Edit: there is one deadlock issue that requires addressing). I agree that adding context restoration is important.

I tried to merge in main, but there are a few minor merge conflicts.

Can you please address those and do the deduplication the bot reviewers have highlighted?

Once that's taken care of, I'll merge in your PR and cut version 0.3.0.

Thanks!

[gfmio]

Can you please address the two issues? The potential deadlock issue is a definite blocker as it stands.

[spumer]

@gfmio deadlock tests implemented and i found a way to exclude ThreadPoolExecutor from implementation.

loop.call_soon / direct call -> loop.call_soon_threadsafe

This allow switch between EvenLoop greenlet and otherone, like between threads. So, detailed overview in module docstring.

This allow us use "await future" without locking forever.

You can replace call_soon_threadsafe back to direct call / call_soon and re-run tests, you will got a deadlock.

[spumer]

Before that call_soon_threadsafe was called in ThreadPoolExecutor (greenlet.join).

When a spawned greenlet completes, TWO events occur in parallel:

Path 1 (link callback):
greenlet dies → link → future.set_result()
→ call_soon(__wakeup) → in _ready, BUT WITHOUT _write_to_self ✗

Path 2 (executor):
greenlet dies → greenlet.join() returns → executor worker completes
→ concurrent.futures.Future resolves
→ asyncio.wrap_future → call_soon_threadsafe(...)
→ _write_to_self() → self-pipe → selector wakes up! ✓

UPD: good article about asyncio event loop and self-pipe mechanics: https://habr.com/ru/articles/995032/

[spumer]

Can we run tests or review via AI?