Fix hot reloading for Python 3.9

[MtkN1]

Fixes #178

1. Move asyncio.Event creation to lifespan

This PR moves the creation of the asyncio.Event from RebuildServer.__init__ to RebuildServer.lifespan. This ensures asyncio.Event is created within the event loop context, resolving the relevant error.

[!NOTE] The error does not occur in Python>=3.10 because the implementation was changed by python/cpython#86558.

2. Add rebuild test

Since there was no rebuild test, I added one.

• Added a rebuild test.
  • Added a test to check refresh messages from /websocket-reload after modifying the index.rst file.
• Changed the target test function to an asynchronous function.
  • Starlette's TestClient uses threads, while RebuildServer uses multiprocessing. In my view, this affected the rebuild test execution and cause it to fail. (0662fc9)
  • Changed Starlette's TestClient to http.AsyncClient. (ref)
  • Added test dependencies asgi-lifespan and httpx-ws required for testing lifespan and WebSocket.

[z-aki]

@AA-Turner @hugovk requesting a review.

[hugovk]

I'm not a maintainer here, but Python 3.9 is only receiving security updates and is EOL in October:

https://devguide.python.org/versions/

And Sphinx itself supports 3.11+:

https://www.sphinx-doc.org/en/master/internals/release-process.html#python-version-support-policy

Can you upgrade to a newer Python?

[MtkN1]

Thank you for your comment.

sphinx-autobuild itself requires Python >= 3.9, and many library projects have this requirement. Therefore, it still has value for at least half a year. I am not particularly attached to Python 3.9, but I believe the changes in the implementation are reasonable. Additionally, I have added tests for hot reload, which may also be valuable for this project.

I would appreciate it if a maintainer could review the changes.

[hugovk]

Thank you for your comment.

sphinx-autobuild itself requires Python >= 3.9, and many library projects have this requirement. Therefore, it still has value for at least half a year. I am not particularly attached to Python 3.9, but I believe the changes in the implementation are reasonable.

Because Sphinx is an application for generating docs, and not a library dependency, projects can build docs with a single (recent) Python version, even if they support the full 3.9-3.13 range.

I've opened https://github.com/sphinx-doc/sphinx-autobuild/pull/189 as an alternative to match the same versions as Sphinx itself, in case the maintainers wish to keep parity.

Additionally, I have added tests for hot reload, which may also be valuable for this project.

Yes, these sound useful.