code/autoslm/_logging.py

"""Package logging helpers.

Library code logs through the ``autoslm`` logger and never configures handlers on import (it
attaches a :class:`logging.NullHandler`), so importing AutoSLM stays silent for downstream
applications. The CLI calls :func:`configure_logging` to attach a console handler whose
level is controlled by ``-v/--verbose`` or the ``AUTOSLM_LOG_LEVEL`` environment variable.
"""

from __future__ import annotations

import logging
import os

_ROOT_NAME = "autoslm"

# Attach a NullHandler once so "No handlers could be found" warnings never appear and
# importing the library produces no output unless the app opts in.
_root = logging.getLogger(_ROOT_NAME)
if not any(isinstance(h, logging.NullHandler) for h in _root.handlers):
    _root.addHandler(logging.NullHandler())


def get_logger(name: str | None = None) -> logging.Logger:
    """Return a logger under the ``autoslm`` namespace (e.g. ``get_logger(__name__)``)."""
    if not name or name == _ROOT_NAME:
        return logging.getLogger(_ROOT_NAME)
    if name.startswith(_ROOT_NAME + "."):
        return logging.getLogger(name)
    return logging.getLogger(f"{_ROOT_NAME}.{name}")


def _level_from_env(default: int = logging.WARNING) -> int:
    raw = os.environ.get("AUTOSLM_LOG_LEVEL")
    if not raw:
        return default
    raw = raw.strip()
    if raw.isdigit():
        return int(raw)
    # Map names (INFO/DEBUG/...) to ints via the canonical name->level mapping rather
    # than logging.getLevelName, whose name->int behaviour is deprecated and which
    # returns "Level FOO" for unknown names instead of signalling failure.
    return logging.getLevelNamesMapping().get(raw.upper(), default)


def configure_logging(verbosity: int = 0, level: int | None = None) -> None:
    """Attach a console handler to the ``autoslm`` logger and set its level.

    ``verbosity`` maps repeated ``-v`` flags to levels (0=WARNING, 1=INFO, >=2=DEBUG).
    An explicit ``level`` (or the ``AUTOSLM_LOG_LEVEL`` env var) overrides the verbosity mapping.
    """
    if level is None:
        if os.environ.get("AUTOSLM_LOG_LEVEL"):
            level = _level_from_env()
        else:
            level = {0: logging.WARNING, 1: logging.INFO}.get(verbosity, logging.DEBUG)

    logger = logging.getLogger(_ROOT_NAME)
    logger.setLevel(level)
    # Replace any prior console handler we installed so repeated calls don't stack handlers.
    for h in [h for h in logger.handlers if getattr(h, "_autoslm_console", False)]:
        logger.removeHandler(h)
    handler = logging.StreamHandler()  # stderr
    handler.setLevel(level)
    handler.setFormatter(logging.Formatter("%(levelname)s %(name)s: %(message)s"))
    handler._autoslm_console = True  # type: ignore[attr-defined]
    logger.addHandler(handler)