Cython compilation error with const variable assignments in datetime.pyx (commit a29a6f6a)

まだ誰も着手していません。

When building from a29a6f6aaa09013cb33ffadb8dd57e21d671ab55 there are compilation errors on 3.12. On relatively newer versions of cython declaring a `const` at module initialization has been deprecated.

```bash
Error compiling Cython file:
------------------------------------------------------------
...
pg_epoch_date = datetime.date(2000, 1, 1)
cdef int32_t pg_date_offset_ord = \
cpython.PyLong_AsLong(pg_epoch_date.toordinal())

# Binary representations of infinity for datetimes.
cdef const int64_t pg_time64_infinity = 0x7fffffffffffffff
^
------------------------------------------------------------

asyncpg/pgproto/./codecs/datetime.pyx:30:5: Assignment to const 'pg_time64_infinity'

Error compiling Cython file:
------------------------------------------------------------
...
cdef int32_t pg_date_offset_ord = \
cpython.PyLong_AsLong(pg_epoch_date.toordinal())

# Binary representations of infinity for datetimes.
cdef const int64_t pg_time64_infinity = 0x7fffffffffffffff
cdef const int64_t pg_time64_negative_infinity = 0x8000000000000000
^
------------------------------------------------------------

asyncpg/pgproto/./codecs/datetime.pyx:31:5: Assignment to const 'pg_time64_negative_infinity'

Error compiling Cython file:
------------------------------------------------------------
...
cpython.PyLong_AsLong(pg_epoch_date.toordinal())

# Binary representations of infinity for datetimes.
cdef const int64_t pg_time64_infinity = 0x7fffffffffffffff
cdef const int64_t pg_time64_negative_infinity = 0x8000000000000000
cdef const int32_t pg_date_infinity = 0x7fffffff
^
------------------------------------------------------------

asyncpg/pgproto/./codecs/datetime.pyx:32:5: Assignment to const 'pg_date_infinity'

Error compiling Cython file:
------------------------------------------------------------
...

# Binary representations of infinity for datetimes.
cdef const int64_t pg_time64_infinity = 0x7fffffffffffffff
cdef const int64_t pg_time64_negative_infinity = 0x8000000000000000
cdef const int32_t pg_date_infinity = 0x7fffffff
cdef const int32_t pg_date_negative_infinity = 0x80000000
^
------------------------------------------------------------

asyncpg/pgproto/./codecs/datetime.pyx:33:5: Assignment to const 'pg_date_negative_infinity'
Compiling asyncpg/pgproto/pgproto.pyx because it changed.
Compiling asyncpg/protocol/protocol.pyx because it changed.
[1/2] Cythonizing asyncpg/pgproto/pgproto.pyx
Traceback (most recent call last):
File "/usr/local/lib/python3.12/site-packages/pip/_vendor/pyproject_hooks/_in_process/_in_process.py", line 389, in
main()
File "/usr/local/lib/python3.12/site-packages/pip/_vendor/pyproject_hooks/_in_process/_in_process.py", line 373, in main
json_out["return_val"] = hook(**hook_input["kwargs"])
^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/usr/local/lib/python3.12/site-packages/pip/_vendor/pyproject_hooks/_in_process/_in_process.py", line 175, in prepare_metadata_for_build_wheel
return hook(metadata_directory, config_settings)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/usr/local/lib/python3.12/site-packages/setuptools/build_meta.py", line 374, in prepare_metadata_for_build_wheel
self.run_setup()
File "/usr/local/lib/python3.12/site-packages/setuptools/build_meta.py", line 317, in run_setup
exec(code, locals())
File "", line 234, in
File "/usr/local/lib/python3.12/site-packages/setuptools/__init__.py", line 115, in setup
return distutils.core.setup(**attrs)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/usr/local/lib/python3.12/site-packages/setuptools/_distutils/core.py", line 186, in setup
return run_commands(dist)
^^^^^^^^^^^^^^^^^^
File "/usr/local/lib/python3.12/site-packages/setuptools/_distutils/core.py", line 202, in run_commands
dist.run_commands()
File "/usr/local/lib/python3.12/site-packages/setuptools/_distutils/dist.py", line 1002, in run_commands
self.run_command(cmd)
File "/usr/local/lib/python3.12/site-packages/setuptools/dist.py", line 1102, in run_command
super().run_command(command)
File "/usr/local/lib/python3.12/site-packages/setuptools/_distutils/dist.py", line 1021, in run_command
cmd_obj.run()
File "/usr/local/lib/python3.12/site-packages/setuptools/command/dist_info.py", line 94, in run
self.egg_info.run()
File "/usr/local/lib/python3.12/site-packages/setuptools/command/egg_info.py", line 312, in run
self.find_sources()
File "/usr/local/lib/python3.12/site-packages/setuptools/command/egg_info.py", line 320, in find_sources
mm.run()
File "/usr/local/lib/python3.12/site-packages/setuptools/command/egg_info.py", line 543, in run
self.add_defaults()
File "/usr/local/lib/python3.12/site-packages/setuptools/command/egg_info.py", line 581, in add_defaults
sdist.add_defaults(self)
File "/usr/local/lib/python3.12/site-packages/setuptools/command/sdist.py", line 109, in add_defaults
super().add_defaults()
File "/usr/local/lib/python3.12/site-packages/setuptools/_distutils/command/sdist.py", line 245, in add_defaults
self._add_defaults_ext()
File "/usr/local/lib/python3.12/site-packages/setuptools/_distutils/command/sdist.py", line 329, in _add_defaults_ext
build_ext = self.get_finalized_command('build_ext')
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/usr/local/lib/python3.12/site-packages/setuptools/_distutils/cmd.py", line 334, in get_finalized_command
cmd_obj.ensure_finalized()
File "/usr/local/lib/python3.12/site-packages/setuptools/_distutils/cmd.py", line 135, in ensure_finalized
self.finalize_options()
File "", line 216, in finalize_options
File "/usr/local/lib/python3.12/site-packages/Cython/Build/Dependencies.py", line 1154, in cythonize
cythonize_one(*args)
File "/usr/local/lib/python3.12/site-packages/Cython/Build/Dependencies.py", line 1321, in cythonize_one
raise CompileError(None, pyx_file)
Cython.Compiler.Errors.CompileError: asyncpg/pgproto/pgproto.pyx
error: subprocess-exited-with-error

× Preparing metadata (pyproject.toml) did not run successfully.
│ exit code: 1
╰─> No available output.

note: This error originates from a subprocess, and is likely not a problem with pip.
full command: /usr/local/bin/python3.12 /usr/local/lib/python3.12/site-packages/pip/_vendor/pyproject_hooks/_in_process/_in_process.py prepare_metadata_for_build_wheel /tmp/tmpk5opk_pk
cwd: /tmp/eugo/asyncpg
Preparing metadata (pyproject.toml) ... error
error: metadata-generation-failed
```

## Fix

Remove the `const` keyword from lines 30-33 in `codecs/datetime.pyx`:
```cython
# Change from:
cdef const int64_t pg_time64_infinity = 0x7fffffffffffffff
cdef const int64_t pg_time64_negative_infinity = 0x8000000000000000
cdef const int32_t pg_date_infinity = 0x7fffffff
cdef const int32_t pg_date_negative_infinity = 0x80000000

# To:
cdef int64_t pg_time64_infinity = 0x7fffffffffffffff
cdef int64_t pg_time64_negative_infinity = 0x8000000000000000
cdef int32_t pg_date_infinity = 0x7fffffff
cdef int32_t pg_date_negative_infinity = 0x80000000
```

asyncpg/pgproto/codecs/datetime.pyx の 30-33 行目から始め、コンパイルエラーで示されている Cython 宣言を確認します。Python 3.12 のビルドまたは metadata-generation コマンドを再実行し、const-assignment errors なしでコンパイルが成功することを確認します。パッケージのビルドが正常に成功すれば完了です。

索引モデルが issue の本文から書いたものです。