add basic sphinx & readthedocs infra

.readthedocs.yaml

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+---
+# .readthedocs.yaml
+# Read the Docs configuration file
+# See https://docs.readthedocs.io/en/stable/config-file/v2.html for details
+
+# Required
+version: 2
+
+# Set the OS, Python version and other tools you might need
+build:
+    os: ubuntu-lts-latest
+    tools:
+        python: latest
+    # You can also specify other tool versions:
+    # nodejs: "19"
+    # rust: "1.64"
+    # golang: "1.19"
+
+# Build documentation in the "docs/" directory with Sphinx
+sphinx:
+    configuration: docs/conf.py
+
+# Optionally build your docs in additional formats such as PDF and ePub
+# formats:
+#    - pdf
+#    - epub
+
+# Optional but recommended, declare the Python requirements required
+# to build your documentation
+# See https://docs.readthedocs.io/en/stable/guides/reproducible-builds.html
+python:
+    install:
+        - requirements: docs/requirements.txt

docs/Makefile

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+# Minimal makefile for Sphinx documentation
+#
+
+# You can set these variables from the command line, and also
+# from the environment for the first two.
+SPHINXOPTS    ?=
+SPHINXBUILD   ?= sphinx-build
+SOURCEDIR     = .
+BUILDDIR      = _build
+
+# Put it first so that "make" without argument is like "make help".
+help:
+	@$(SPHINXBUILD) -M help "$(SOURCEDIR)" "$(BUILDDIR)" $(SPHINXOPTS) $(O)
+
+.PHONY: help Makefile
+
+# Catch-all target: route all unknown targets to Sphinx using the new
+# "make mode" option.  $(O) is meant as a shortcut for $(SPHINXOPTS).
+%: Makefile
+	@$(SPHINXBUILD) -M $@ "$(SOURCEDIR)" "$(BUILDDIR)" $(SPHINXOPTS) $(O)

docs/__init__.py

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+"""Documentation for flake8-async.
+
+Ruff raised INP001 "implicit namespace package" without this file.
+"""

docs/conf.py

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+"""Configuration file for the Sphinx documentation builder.
+
+For the full list of built-in configuration values, see the documentation:
+https://www.sphinx-doc.org/en/master/usage/configuration.html
+"""
+
+import sys
+from pathlib import Path
+
+sys.path.insert(0, str(Path("..").resolve()))
+import flake8_async
+
+# -- Project information -----------------------------------------------------
+# https://www.sphinx-doc.org/en/master/usage/configuration.html#project-information
+
+project = "flake8-async"
+# A001: shadowing python builtin
+copyright = "2024, Zac Hatfield-Dodds, John Litborn, and Contributors"  # noqa: A001
+author = "Zac Hatfield-Dodds, John Litborn, and Contributors"
+
+
+version = flake8_async.__version__
+release = version
+
+# -- General configuration ---------------------------------------------------
+# https://www.sphinx-doc.org/en/master/usage/configuration.html#general-configuration
+
+extensions: list[str] = []
+
+templates_path = ["_templates"]
+exclude_patterns: list[str] = ["_build", "Thumbs.db", ".DS_Store"]
+
+# Warn about all references to unknown targets
+nitpicky = True
+
+
+# -- Options for HTML output -------------------------------------------------
+# https://www.sphinx-doc.org/en/master/usage/configuration.html#options-for-html-output
+
+html_theme = "alabaster"
+# We don't currently use the _static directory, and git doesn't allow empty directories,
+# so leaving it commented out for now to silence a warning.
+# `html_static_path = ["_static"]`

docs/index.rst

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+.. flake8-async documentation master file, created by
+   sphinx-quickstart on Wed Mar 20 13:37:26 2024.
+   You can adapt this file completely to your liking, but it should at least
+   contain the root `toctree` directive.
+
+############
+flake8-async
+############
+
+
+A highly opinionated flake8 plugin for problems related to `Trio <https://github.com/python-trio/trio>`_, `AnyIO <https://github.com/agronholm/anyio>`_, or `asyncio <https://docs.python.org/3/library/asyncio.html>`_.
+
+
+This can include anything from outright bugs, to pointless/dead code,
+to likely performance issues, to minor points of idiom that might signal
+a misunderstanding.
+
+
+The plugin may well be too noisy or pedantic depending on your requirements or opinions, in which case you should consider :ref:`--disable` for those rules.
+Pairs well with flake8-bugbear.
+
+
+Some checks are incorporated into `ruff <https://github.com/astral-sh/ruff>`_.
+
+
+This plugin was previously known as flake8-trio, and there was a separate small plugin known as flake8-async for asyncio. But this plugin was a superset of the checks in flake8-async, and support for anyio was added, so it's now named flake8-async to more properly convey its usage. At the same time all error codes were renamed from TRIOxxx to ASYNCxxx, as was previously used by the old flake8-async.
+
+
+*********
+Contents:
+*********
+.. toctree::
+   :maxdepth: 2
+
+   usage
+   rules
+
+
+******************
+Indices and tables
+******************
+
+* :ref:`genindex`
+* :ref:`modindex`
+* :ref:`search`
+* :doc:`usage`
+* :doc:`rules`

docs/make.bat

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+@ECHO OFF
+
+pushd %~dp0
+
+REM Command file for Sphinx documentation
+
+if "%SPHINXBUILD%" == "" (
+	set SPHINXBUILD=sphinx-build
+)
+set SOURCEDIR=source
+set BUILDDIR=build
+
+%SPHINXBUILD% >NUL 2>NUL
+if errorlevel 9009 (
+	echo.
+	echo.The 'sphinx-build' command was not found. Make sure you have Sphinx
+	echo.installed, then set the SPHINXBUILD environment variable to point
+	echo.to the full path of the 'sphinx-build' executable. Alternatively you
+	echo.may add the Sphinx directory to PATH.
+	echo.
+	echo.If you don't have Sphinx installed, grab it from
+	echo.https://www.sphinx-doc.org/
+	exit /b 1
+)
+
+if "%1" == "" goto help
+
+%SPHINXBUILD% -M %1 %SOURCEDIR% %BUILDDIR% %SPHINXOPTS% %O%
+goto end
+
+:help
+%SPHINXBUILD% -M help %SOURCEDIR% %BUILDDIR% %SPHINXOPTS% %O%
+
+:end
+popd

docs/requirements.txt

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+libcst

docs/rules.rst

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+List of warnings
+------------------
+
+- **ASYNC100**: A ``with [trio/anyio].fail_after(...):`` or ``with [trio/anyio].move_on_after(...):`` context does not contain any ``await`` statements.  This makes it pointless, as the timeout can only be triggered by a checkpoint. This check also allows ``yield`` statements, since checkpoints can happen in the caller we yield to.
+- **ASYNC101**: ``yield`` inside a trio/anyio nursery or cancel scope is only safe when implementing a context manager - otherwise, it breaks exception handling.
+- **ASYNC102**: It's unsafe to await inside ``finally:`` or ``except BaseException/trio.Cancelled/anyio.get_cancelled_exc_class()/asyncio.exceptions.CancelledError`` unless you use a shielded cancel scope with a timeout. This is currently not able to detect asyncio shields.
+- **ASYNC103**: ``except BaseException/trio.Cancelled/anyio.get_cancelled_exc_class()/asyncio.exceptions.CancelledError``, or a bare ``except:`` with a code path that doesn't re-raise. If you don't want to re-raise ``BaseException``, add a separate handler for ``trio.Cancelled``/``anyio.get_cancelled_exc_class()``/``asyncio.exceptions.CancelledError`` before.
+- **ASYNC104**: ``trio.Cancelled``/``anyio.get_cancelled_exc_class()``/``asyncio.exceptions.CancelledError``/``BaseException`` must be re-raised. The same as ASYNC103, except specifically triggered on ``return`` or a different exception being raised.
+- **ASYNC105**: Calling a trio async function without immediately ``await``\ ing it. This is only supported with trio functions, but you can get similar functionality with a type-checker.
+- **ASYNC106**: ``trio``/``anyio``/``asyncio`` must be imported with ``import trio``/``import anyio``/``import asyncio`` for the linter to work.
+- **ASYNC109**: Async function definition with a ``timeout`` parameter - use ``[trio/anyio].[fail/move_on]_[after/at]`` instead.
+- **ASYNC110**: ``while <condition>: await [trio/anyio].sleep()`` should be replaced by a ``[trio/anyio].Event``.
+- **ASYNC111**: Variable, from context manager opened inside nursery, passed to ``start[_soon]`` might be invalidly accessed while in use, due to context manager closing before the nursery. This is usually a bug, and nurseries should generally be the inner-most context manager.
+- **ASYNC112**: Nursery body with only a call to ``nursery.start[_soon]`` and not passing itself as a parameter can be replaced with a regular function call.
+- **ASYNC113**: Using ``nursery.start_soon`` in ``__aenter__`` doesn't wait for the task to begin. Consider replacing with ``nursery.start``.
+- **ASYNC114**: Startable function (i.e. has a ``task_status`` keyword parameter) not in ``--startable-in-context-manager`` parameter list, please add it so ASYNC113 can catch errors when using it.
+- **ASYNC115**: Replace ``[trio/anyio].sleep(0)`` with the more suggestive ``[trio/anyio].lowlevel.checkpoint()``.
+- **ASYNC116**: ``[trio/anyio].sleep()`` with >24 hour interval should usually be ``[trio/anyio].sleep_forever()``.
+- **ASYNC118**: Don't assign the value of ``anyio.get_cancelled_exc_class()`` to a variable, since that breaks linter checks and multi-backend programs.
+
+Warnings for blocking sync calls in async functions
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Note: 22X, 23X and 24X has not had asyncio-specific suggestions written.
+
+
+- **ASYNC200**: User-configured error for blocking sync calls in async functions. Does nothing by default, see :ref:`async200-blocking-calls` for how to configure it.
+- **ASYNC210**: Sync HTTP call in async function, use ``httpx.AsyncClient``. This and the other ASYNC21x checks look for usage of ``urllib3`` and ``httpx.Client``, and recommend using ``httpx.AsyncClient`` as that's the largest http client supporting anyio/trio.
+- **ASYNC211**: Likely sync HTTP call in async function, use ``httpx.AsyncClient``. Looks for ``urllib3`` method calls on pool objects, but only matching on the method signature and not the object.
+- **ASYNC212**: Blocking sync HTTP call on httpx object, use httpx.AsyncClient.
+- **ASYNC220**: Sync process call in async function, use ``await nursery.start([trio/anyio].run_process, ...)``. ``asyncio`` users can use `asyncio.create_subprocess_[exec/shell] <https://docs.python.org/3/library/asyncio-subprocess.html>`_.
+- **ASYNC221**: Sync process call in async function, use ``await [trio/anyio].run_process(...)``. ``asyncio`` users can use `asyncio.create_subprocess_[exec/shell] <https://docs.python.org/3/library/asyncio-subprocess.html>`_.
+- **ASYNC222**: Sync ``os.*`` call in async function, wrap in ``await [trio/anyio].to_thread.run_sync()``. ``asyncio`` users can use `asyncio.loop.run_in_executor <https://docs.python.org/3/library/asyncio-subprocess.html>`_.
+- **ASYNC230**: Sync IO call in async function, use ``[trio/anyio].open_file(...)``. ``asyncio`` users need to use a library such as `aiofiles <https://pypi.org/project/aiofiles/>`_, or switch to `anyio <https://github.com/agronholm/anyio>`_.
+- **ASYNC231**: Sync IO call in async function, use ``[trio/anyio].wrap_file(...)``. ``asyncio`` users need to use a library such as `aiofiles <https://pypi.org/project/aiofiles/>`_, or switch to `anyio <https://github.com/agronholm/anyio>`_.
+- **ASYNC232**: Blocking sync call on file object, wrap the file object in ``[trio/anyio].wrap_file()`` to get an async file object.
+- **ASYNC240**: Avoid using ``os.path`` in async functions, prefer using ``[trio/anyio].Path`` objects. ``asyncio`` users should consider `aiopath <https://pypi.org/project/aiopath>`_ or `anyio <https://github.com/agronholm/anyio>`_.
+- **ASYNC250**: Builtin ``input()`` should not be called from async function. Wrap in ``[trio/anyio].to_thread.run_sync()`` or ``asyncio.loop.run_in_executor()``.
+- **ASYNC251**: ``time.sleep(...)`` should not be called from async function. Use ``[trio/anyio/asyncio].sleep(...)``.
+
+Warnings disabled by default
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+- **ASYNC900**: Async generator without ``@asynccontextmanager`` not allowed. You might want to enable this on a codebase since async generators are inherently unsafe and cleanup logic might not be performed. See https://github.com/python-trio/flake8-async/issues/211 and https://discuss.python.org/t/using-exceptiongroup-at-anthropic-experience-report/20888/6 for discussion.
+- **ASYNC910**: Exit or ``return`` from async function with no guaranteed checkpoint or exception since function definition. You might want to enable this on a codebase to make it easier to reason about checkpoints, and make the logic of ASYNC911 correct.
+- **ASYNC911**: Exit, ``yield`` or ``return`` from async iterable with no guaranteed checkpoint since possible function entry (yield or function definition)
+  Checkpoints are ``await``, ``async for``, and ``async with`` (on one of enter/exit).
+
+Removed warnings
+~~~~~~~~~~~~~~~~
+
+- **TRIOxxx**: All error codes are now renamed ASYNCxxx
+- **TRIO107**: Renamed to TRIO910
+- **TRIO108**: Renamed to TRIO911
+- **TRIO117**: Don't raise