fix unsupported logging format check

doc/whatsnew/fragments/10752.false_positive

@@ -0,0 +1,5 @@
+Fixed false positive for ``logging-unsupported-format`` when no arguments are provided to logging functions.
+
+According to Python's logging documentation, no formatting is performed when no arguments are supplied, so strings like ``logging.error("%test")`` are valid.
+
+Closes #10752

pylint/checkers/logging.py

@@ -355,12 +355,16 @@ def _check_format_string(self, node: nodes.Call, format_arg: Literal[0, 1]) -> N
                         keyword_args_cnt + implicit_pos_args + explicit_pos_args
                     )
             except utils.UnsupportedFormatCharacter as ex:
-                char = format_string[ex.index]
-                self.add_message(
-                    "logging-unsupported-format",
-                    node=node,
-                    args=(char, ord(char), ex.index),
-                )
+                if num_args > 0:
+                    # Only report unsupported format characters if arguments are provided
+                    # When no arguments are supplied, no formatting is performed
+                    # https://docs.python.org/3/library/logging.html#logging.Logger.debug
+                    char = format_string[ex.index]
+                    self.add_message(
+                        "logging-unsupported-format",
+                        node=node,
+                        args=(char, ord(char), ex.index),
+                    )
                 return
             except utils.IncompleteFormatString:
                 self.add_message("logging-format-truncated", node=node)