Py313 replace pkgutil get loader for 3.14 - #130

Three commits.

1. Replace pkgutil.get_loader for 3.14

postgresql/python/command.py does from pkgutil import get_loader as module_loader. pkgutil.get_loader was deprecated in Python 3.12 and removed in 3.14, so on 3.14

>>> import postgresql.python.command
ImportError: cannot import name 'get_loader' from 'pkgutil'

which also takes down postgresql.bin.pg_python (the pg_python script). On 3.12/3.13 it emits a DeprecationWarning on every -m/-C module: use.

The change defines module_loader(name) on top of importlib.util.find_spec() (available since 3.4, so fine for requires-python >= 3.7), returning the spec's loader or None, which is what Execution expects.

2. Always set version; fixes pg_dotconf import

postgresql/__init__.py does

from .project import version_info, version, \
    author as __author__, date as __date__
__version__ = version

inside try/except ImportError. project.py no longer defines author or date, so the import fails after binding version and before __version__ is set; the error is swallowed. As a result, on any Python version:

>>> import postgresql.bin.pg_dotconf
ImportError: cannot import name '__version__' from 'postgresql'
>>> from postgresql import *
AttributeError: module 'postgresql' has no attribute '__author__'

The change imports only version_info and version, sets __version__ after the try, and drops __author__/__date__ from __all__.

3. Fix pg_dotconf -f/--file

With the import fixed, pg_dotconf -f settings.conf postgresql.conf hits NameError: name 'comment' is not defined: the loop uses bare comment and unquote instead of configfile.comment/configfile.unquote. It also tested line[pl[0].start] (the first character of the key) for the comment marker, so a commented-out setting in the settings file would have been applied. It now checks line[:pl[0].start], as configfile.alter_config() does.

Testing

Driving postgresql.python.command.command() directly with ['pg_python', '-C', 'module:pgcmd_ctx', '-m', 'pgcmd_main', 'a1', 'a2'] (two small throwaway modules on sys.path), plus -m no_such_module_xyz, with DeprecationWarning turned into errors:

• Before (f71e4b2): 3.14.3 -> ImportError on import; 3.12.13 and 3.13.14 -> DeprecationWarning: 'pkgutil.get_loader' is deprecated and slated for removal in Python 3.14.
• After, CPython 3.12.13, 3.13.14 and 3.14.3: main module runs as __main__ with argv ['a1', 'a2'] and the context module's globals, returns 0; the missing module raises ImportError: Python module 'no_such_module_xyz' does not exist or cannot be read as before.
• python -m unittest postgresql.test.test_python: OK on all three.

Commits 2 and 3: import postgresql, from postgresql import *, then pg_dotconf.command(['pg_dotconf', '--stdout', '-f', 'settings.conf', 'postgresql.conf']) with a settings file holding port = 5433 and #work_mem = 64MB, and a postgresql.conf holding #port = 5432, max_connections = 100, #work_mem = 4MB:

• Before (f71e4b2 + commit 1): __version__ missing, star import AttributeError, import postgresql.bin.pg_dotconf ImportError (CPython 3.12.13 and 3.13.14).
• After commit 2 only: NameError comment in command().
• After commit 3, CPython 3.12.13, 3.13.14 and 3.14.3: __version__ == '1.3.1', star import OK, output port = '5433', max_connections = 100, #work_mem = 4MB (the commented work_mem line in the settings file is skipped).
• python -m unittest postgresql.test.test_configfile: OK on all three.