logging: make log levels/format configurable

This allows users to prevent the root logger from swallowing logs, for
example logs emitted by plugins and dependencies (such as the
MusicBrainz API client).

Author: 9999years

beets/logging.py

@@ -29,10 +29,12 @@
     WARNING,
     FileHandler,
     Filter,
+    Formatter,
     Handler,
     Logger,
     NullHandler,
     StreamHandler,
+    _levelToName,
 )
 
 __all__ = [
@@ -42,14 +44,28 @@
     "WARNING",
     "FileHandler",
     "Filter",
+    "Formatter",
     "Handler",
     "Logger",
     "NullHandler",
     "StreamHandler",
     "getLogger",
+    "getLevelNamesMapping",
 ]
 
 
+def getLevelNamesMapping() -> dict[str, int]:
+    """Returns a mapping from level names to their corresponding logging
+    levels. For example, the string “CRITICAL” maps to CRITICAL. The returned
+    mapping is copied from an internal mapping on each call to this function.
+
+    Polyfill for `logging.getLevelNamesMapping`, which was only added in Python
+    3.11.
+    """
+
+    return {name: level for (level, name) in _levelToName.items()}
+
+
 def logsafe(val):
     """Coerce `bytes` to `str` to avoid crashes solely due to logging.
 

beets/ui/__init__.py

@@ -29,7 +29,7 @@
 import textwrap
 import traceback
 from difflib import SequenceMatcher
-from typing import TYPE_CHECKING, Any, Callable
+from typing import TYPE_CHECKING, Any, Callable, OrderedDict, cast
 
 import confuse
 
@@ -1637,13 +1637,7 @@ def _configure(options):
         overlay_path = None
     config.set_args(options)
 
-    beet_logger = logging.getLogger("beets")
-
-    # Configure the logger.
-    if config["verbose"].get(int):
-        beet_logger.set_global_level(logging.DEBUG)
-    else:
-        beet_logger.set_global_level(logging.INFO)
+    _configure_logging()
 
     if overlay_path:
         log.debug(
@@ -1663,6 +1657,72 @@ def _configure(options):
     return config
 
 
+def _configure_logging():
+    """Configure logging levels and handlers."""
+
+    if config["verbose"].get(int):
+        level = logging.DEBUG
+    else:
+        level = logging.INFO
+
+    root_logger = logging.getLogger()
+    beet_logger = logging.getLogger("beets")
+
+    root_logger.setLevel(level)
+    beet_logger.set_global_level(level)
+
+    log_format = config["logging"]["format"].get(
+        confuse.String(default="{message}")
+    )
+    date_format = config["logging"]["date_format"].get(
+        confuse.String(default="%Y-%m-%d %H:%M:%S")
+    )
+
+    # Remove the `StreamHandler` we added earlier so we can make a new one with
+    # the user's format.
+    for logger in [log, beet_logger, root_logger]:
+        stream_handlers = [
+            handler
+            for handler in logger.handlers
+            if isinstance(handler, logging.StreamHandler)
+        ]
+        for handler in stream_handlers:
+            logger.removeHandler(handler)
+
+        handler = logging.StreamHandler()
+        handler.setFormatter(
+            logging.Formatter(
+                fmt=cast(str, log_format),
+                datefmt=cast(str, date_format),
+                style="{",
+                validate=True,
+            )
+        )
+        logger.addHandler(handler)
+
+    level_names_mapping = logging.getLevelNamesMapping()
+    log_levels = config["logging"]["levels"].get(
+        confuse.MappingValues(
+            confuse.OneOf(
+                allowed=[
+                    confuse.Integer(),
+                    confuse.OneOf(allowed=level_names_mapping.keys()),
+                ]
+            )
+        )
+    )
+
+    if log_levels:
+        for name, level in cast(OrderedDict, log_levels).items():
+            name = None if name == "root" else name
+            logger = logging.getLogger(name)
+            if isinstance(level, str):
+                level = level_names_mapping[level]
+            logger.setLevel(level)
+            if hasattr(logger, "set_global_level"):
+                logger.set_global_level(level)
+
+
 def _ensure_db_directory_exists(path):
     if path == b":memory:":  # in memory db
         return