Add --debug argument to CLI to make the THING LOGGER level configurable between debug and info. Unit test also added.

Author: bprobert97

src/labthings_fastapi/logs.py

@@ -79,11 +79,11 @@ def emit(self, record: logging.LogRecord) -> None:
                 pass  # If there's no destination for a particular log, ignore it.
 
 
-def configure_thing_logger() -> None:
+def configure_thing_logger(level: int | None = None) -> None:
     """Set up the logger for thing instances.
 
-    We always set the logger for thing instances to level INFO, as this
-    is currently used to relay progress to the client.
+    We always set the logger for thing instances to level INFO by default,
+    as this is currently used to relay progress to the client.
 
     This function will collect logs on a per-invocation
     basis by adding a `.DequeByInvocationIDHandler` to the log. Only one
@@ -93,8 +93,15 @@ def configure_thing_logger() -> None:
     a filter to add invocation ID is not possible. Instead, we attach a filter to
     the handler, which filters all the records that propagate to it (i.e. anything
     that starts with ``labthings_fastapi.things``).
+
+    :param level: the logging level to use. If not specified, we use the
+        current level, or INFO if no level has been set.
     """
-    THING_LOGGER.setLevel(logging.INFO)
+    if level is not None:
+        THING_LOGGER.setLevel(level)
+    elif THING_LOGGER.level == logging.NOTSET:
+        THING_LOGGER.setLevel(logging.INFO)
+
     if not any(
         isinstance(h, DequeByInvocationIDHandler) for h in THING_LOGGER.handlers
     ):

src/labthings_fastapi/server/cli.py

@@ -19,6 +19,7 @@
 """
 
 from argparse import ArgumentParser, Namespace
+import logging
 import sys
 from typing import Literal, Optional, overload
 
@@ -28,6 +29,7 @@
 from . import ThingServer
 from . import fallback
 from .config_model import ThingServerConfig, ThingImportFailure
+from ..logs import configure_thing_logger
 
 
 def get_default_parser() -> ArgumentParser:
@@ -56,6 +58,11 @@ def get_default_parser() -> ArgumentParser:
         default=5000,
         help="Bind socket to this port. If 0, an available port will be picked.",
     )
+    parser.add_argument(
+        "--debug",
+        action="store_true",
+        help="Enable debug logging.",
+    )
     return parser
 
 
@@ -149,6 +156,9 @@ def serve_from_cli(
         option is not specified.
     """
     args = parse_args(argv)
+    if args.debug:
+        configure_thing_logger(logging.DEBUG)
+
     try:
         config, server = None, None
         config = config_from_args(args)

tests/test_cli_debug.py

@@ -0,0 +1,27 @@
+import logging
+from labthings_fastapi.server.cli import serve_from_cli
+from labthings_fastapi.logs import THING_LOGGER
+
+def test_cli_debug_flag():
+    """
+    Test that using the --debug flag sets the logger level to DEBUG,
+    and that not using it leaves the logger level at INFO.
+    """
+    # Reset logger level to NOTSET
+    THING_LOGGER.setLevel(logging.NOTSET)
+
+    # Run without --debug
+    # We use dry_run=True to avoid starting uvicorn
+    # We need a dummy config
+    dummy_json = '{"things": {}}'
+    serve_from_cli(["--json", dummy_json], dry_run=True)
+
+    assert THING_LOGGER.level == logging.INFO
+
+    # Reset logger level
+    THING_LOGGER.setLevel(logging.NOTSET)
+
+    # Run with --debug
+    serve_from_cli(["--json", dummy_json, "--debug"], dry_run=True)
+
+    assert THING_LOGGER.level == logging.DEBUG