fix(logger): fix exception on flush without buffer (aws-powertools#6794)

* fix: exception on flush without buffer

* fix(logger): add test for flush without buffer

Co-authored-by: leandrodamascena <[email protected]>

---------

Co-authored-by: Leandro Damascena <[email protected]>
Co-authored-by: leandrodamascena <[email protected]>

Author: 2 people

aws_lambda_powertools/logging/logger.py

@@ -1200,6 +1200,10 @@ def flush_buffer(self) -> None:
 
         tracer_id = get_tracer_id()
 
+        # no buffer config? return
+        if not self._buffer_config:
+            return
+
         # Flushing log without a tracer id? Return
         if not tracer_id:
             return
@@ -1209,9 +1213,6 @@ def flush_buffer(self) -> None:
         if not buffer:
             return
 
-        if not self._buffer_config:
-            return
-
         # Check ALC level against buffer level
         lambda_log_level = self._get_aws_lambda_log_level()
         if lambda_log_level:

tests/functional/logger/required_dependencies/test_powertools_logger_buffer.py

@@ -391,6 +391,30 @@ def handler(event, context):
     assert len(log) == 0
 
 
+def test_flush_buffer_log_output_without_buffer_config(stdout, service_name, lambda_context, monkeypatch):
+    # Set initial trace ID for first Lambda invocation
+    monkeypatch.setenv(constants.XRAY_TRACE_ID_ENV, "1-67c39786-5908a82a246fb67f3089263f")
+
+    # GIVEN A logger without buffer configuration
+    logger = Logger(level="DEBUG", service=service_name, stream=stdout)
+
+    @logger.inject_lambda_context(flush_buffer_on_uncaught_error=True)
+    def handler(event, context):
+        # Log messages are not buffered and should be output immediately
+        logger.debug("debug message - 1")
+        logger.debug("debug message - 2")
+        raise ValueError("Test error")
+
+    # WHEN Invoking the handler and expecting a ValueError
+    # AND flush_buffer_on_uncaught_error is True but there is no logger buffer configuration
+    with pytest.raises(ValueError):
+        handler({}, lambda_context)
+
+    # THEN Verify that log messages are flushed without any exception
+    log = capture_multiple_logging_statements_output(stdout)
+    assert len(log) == 2, "Expected two log messages"
+
+
 def test_buffer_configuration_and_buffer_propagation_across_logger_instances(stdout, service_name, monkeypatch):
     monkeypatch.setenv(constants.XRAY_TRACE_ID_ENV, "1-67c39786-5908a82a246fb67f3089263f")