[feat] Detect missing formatting args when the string is not interpolated too

The original decision was taken in db8b3a4 during implementation with
a different rational ("If no args were supplied, then all format strings
are valid don't check any further.") and was not discussed again when the
comment was updated in #2713. I think the new behavior make sense especially
considering that the primer shows 4 false negative in home-assistant.

Co-authored-by: Alex Prabhat Bara <[email protected]>

Author: Pierre-Sassoulas

doc/whatsnew/fragments/9999.false_negative

@@ -0,0 +1,5 @@
+We now raise a ``logging-too-few-args`` for format string with no
+interpolation arguments at all (i.e. for something like ``logging.debug("Awaiting process %s")``
+or ``logging.debug("Awaiting process {pid}")``). Previously we did not raise for such case.
+
+Closes #9999

pylint/checkers/logging.py

@@ -326,11 +326,6 @@ def _check_format_string(self, node: nodes.Call, format_arg: Literal[0, 1]) -> N
           format_arg: Index of the format string in the node arguments.
         """
         num_args = _count_supplied_tokens(node.args[format_arg + 1 :])
-        if not num_args:
-            # If no args were supplied the string is not interpolated and can contain
-            # formatting characters - it's used verbatim. Don't check any further.
-            return
-
         format_string = node.args[format_arg].value
         required_num_args = 0
         if isinstance(format_string, bytes):

tests/functional/l/logging/logging_too_few_args.txt

@@ -1,9 +1,12 @@
-"""Tests for logging-too-few-args"""
+"""Tests for logging-too-few-args new style"""
 
 import logging
 
 logging.error("{}, {}", 1)  # [logging-too-few-args]
 logging.error("{0}, {1}", 1)  # [logging-too-few-args]
+logging.error("{}")  # [logging-too-few-args]
+logging.error("{0}")  # [logging-too-few-args]
+logging.error("{named}")  # [logging-too-few-args]
 logging.error("{named1}, {named2}", {"named1": 1})  # [logging-too-few-args]
 logging.error("{0}, {named}", 1)  # [logging-too-few-args]
 logging.error("{}, {named}", {"named": 1})  # [logging-too-few-args]

tests/functional/l/logging/logging_too_few_args.py renamed to tests/functional/l/logging/logging_too_few_args_new_style.py

@@ -0,0 +1,9 @@
+logging-too-few-args:5:0:5:26::Not enough arguments for logging format string:UNDEFINED
+logging-too-few-args:6:0:6:28::Not enough arguments for logging format string:UNDEFINED
+logging-too-few-args:7:0:7:19::Not enough arguments for logging format string:UNDEFINED
+logging-too-few-args:8:0:8:20::Not enough arguments for logging format string:UNDEFINED
+logging-too-few-args:9:0:9:24::Not enough arguments for logging format string:UNDEFINED
+logging-too-few-args:10:0:10:50::Not enough arguments for logging format string:UNDEFINED
+logging-too-few-args:11:0:11:32::Not enough arguments for logging format string:UNDEFINED
+logging-too-few-args:12:0:12:42::Not enough arguments for logging format string:UNDEFINED
+logging-too-few-args:13:0:13:43::Not enough arguments for logging format string:UNDEFINED

tests/functional/l/logging/logging_too_few_args.rc renamed to tests/functional/l/logging/logging_too_few_args_new_style.rc

@@ -0,0 +1,6 @@
+"""Tests for logging-too-few-args old style"""
+
+import logging
+
+logging.error("%s, %s", 1)  # [logging-too-few-args]
+logging.debug("Sisyphus table %s: sleep")  # [logging-too-few-args]

tests/functional/l/logging/logging_too_few_args_new_style.txt

@@ -0,0 +1,2 @@
+[LOGGING]
+logging-format-style=old

tests/functional/l/logging/logging_too_few_args_old_style.py

@@ -0,0 +1,2 @@
+logging-too-few-args:5:0:5:26::Not enough arguments for logging format string:UNDEFINED
+logging-too-few-args:6:0:6:41::Not enough arguments for logging format string:UNDEFINED