Expose `log_cli` as a CLI parser option.

_pytest/logging.py

@@ -336,9 +336,10 @@ class LoggingPlugin(object):
         create a single one for the entire test session here.
         """
         self._config = config
+        self._stream_logs = None
 
         # enable verbose output automatically if live logging is enabled
-        if self._config.getini('log_cli') and not config.getoption('verbose'):
+        if self._stream_logs_enabled() and not config.getoption('verbose'):
             # sanity check: terminal reporter should not have been loaded at this point
             assert self._config.pluginmanager.get_plugin('terminalreporter') is None
             config.option.verbose = 1
@@ -364,6 +365,12 @@ class LoggingPlugin(object):
         # initialized during pytest_runtestloop
         self.log_cli_handler = None
 
+    def _stream_logs_enabled(self):
+        if self._stream_logs is None:
+            self._stream_logs = self._config.getoption('--log-cli-level') is not None or \
+                    self._config.getini('log_cli')
+        return self._stream_logs
+
     @contextmanager
     def _runtest_for(self, item, when):
         """Implements the internals of pytest_runtest_xxx() hook."""
@@ -438,7 +445,7 @@ class LoggingPlugin(object):
         This must be done right before starting the loop so we can access the terminal reporter plugin.
         """
         terminal_reporter = self._config.pluginmanager.get_plugin('terminalreporter')
-        if self._config.getini('log_cli') and terminal_reporter is not None:
+        if self._stream_logs_enabled() and terminal_reporter is not None:
             capture_manager = self._config.pluginmanager.get_plugin('capturemanager')
             log_cli_handler = _LiveLoggingStreamHandler(terminal_reporter, capture_manager)
             log_cli_format = get_option_ini(self._config, 'log_cli_format', 'log_format')

changelog/3190.feature

@@ -0,0 +1 @@
+Passing `--log-cli-level` in the command-line now automatically activates live logging.

testing/logging/test_reporting.py

@@ -366,6 +366,48 @@ def test_log_cli_ini_level(testdir):
     assert result.ret == 0
 
 
+@pytest.mark.parametrize('cli_args', ['',
+                                      '--log-level=WARNING',
+                                      '--log-file-level=WARNING',
+                                      '--log-cli-level=WARNING'])
+def test_log_cli_auto_enable(testdir, request, cli_args):
+    """Check that live logs are enabled if --log-level or --log-cli-level is passed on the CLI.
+    It should not be auto enabled if the same configs are set on the INI file.
+    """
+    testdir.makepyfile('''
+        import pytest
+        import logging
+
+        def test_log_1():
+            logging.info("log message from test_log_1 not to be shown")
+            logging.warning("log message from test_log_1")
+
+    ''')
+    testdir.makeini('''
+        [pytest]
+        log_level=INFO
+        log_cli_level=INFO
+    ''')
+
+    result = testdir.runpytest(cli_args)
+    if cli_args == '--log-cli-level=WARNING':
+        result.stdout.fnmatch_lines([
+            '*::test_log_1 ',
+            '*-- live log call --*',
+            '*WARNING*log message from test_log_1*',
+            'PASSED *100%*',
+            '=* 1 passed in *=',
+        ])
+        assert 'INFO' not in result.stdout.str()
+    else:
+        result.stdout.fnmatch_lines([
+            '*test_log_cli_auto_enable*100%*',
+            '=* 1 passed in *=',
+        ])
+        assert 'INFO' not in result.stdout.str()
+        assert 'WARNING' not in result.stdout.str()
+
+
 def test_log_file_cli(testdir):
     # Default log file level
     testdir.makepyfile('''