Expose log_cli as a CLI parser option.

_pytest/logging.py

@@ -101,9 +101,14 @@ def add_option_ini(option, dest, default=None, type=None, **kwargs):
         '--log-date-format',
         dest='log_date_format', default=DEFAULT_LOG_DATE_FORMAT,
         help='log date format as used by the logging module.')
-    parser.addini(
-        'log_cli', default=False, type='bool',
-        help='enable log display during test run (also known as "live logging").')
+    add_option_ini(
+        '--log-cli',
+        dest='log_cli',
+        default=False, action='store_true',
+        type='bool',
+        help='enable log display during test run (also known as '
+             '"live logging").'
+    )
     add_option_ini(
         '--log-cli-level',
         dest='log_cli_level', default=None,
@@ -337,8 +342,14 @@ def __init__(self, config):
         """
         self._config = config
 
+        auto_enable_log_stream = self._config.getoption('--log-cli-level')
+        if auto_enable_log_stream is not None:
+            # Explicitely enable log_cli is --log-cli-level was passed on the CLI
+            # It won't be automatically enabled is set on the ini file.
+            config._inicache['log_cli'] = config._parser._inidict['log_cli'] = True
         # enable verbose output automatically if live logging is enabled
-        if self._config.getini('log_cli') and not config.getoption('verbose'):
+        stream_logs = self._config.getoption('log_cli') or self._config.getini('log_cli')
+        if stream_logs is True 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
@@ -425,7 +436,8 @@ def _setup_cli_logging(self):
         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:
+        stream_logs = self._config.getoption('log_cli') or self._config.getini('log_cli')
+        if stream_logs 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 +1,2 @@
+Expose `log_cli` as a CLI parser option.
+Enable live logs if `--log-cli-level` is passed. Setting `log_cli_level` on the INI file has no effect.

testing/logging/test_reporting.py

@@ -345,6 +345,56 @@ def test_log_cli(request):
     assert result.ret == 0
 
 
+@pytest.mark.parametrize('cli_args', ['',
+                                      '--log-stream',
+                                      '--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()
+    elif cli_args == '--log-stream':
+        result.stdout.fnmatch_lines([
+            '*::test_log_1 ',
+            '*-- live log call --*',
+            '*INFO*log message from test_log_1 not to be shown*',
+            '*WARNING*log message from test_log_1*',
+            'PASSED *100%*',
+            '=* 1 passed in *=',
+        ])
+    else:
+        result.stdout.fnmatch_lines([
+            '*test_log_cli_auto_enable*100%*',
+            '=* 1 passed in *=',
+        ])
+
+
 def test_log_file_cli(testdir):
     # Default log file level
     testdir.makepyfile('''