application: Pass returned prelim options to .configure_logging()

The verbosity and output file options can be obtained from options
returned by `.parse_preliminary_options_and_args()`, instead of state
from the `Application` object.

src/flake8/api/legacy.py

@@ -28,10 +28,10 @@ def get_style_guide(**kwargs):
         :class:`StyleGuide`
     """
     application = app.Application()
-    application.parse_preliminary_options_and_args([])
-    flake8.configure_logging(
-        application.prelim_opts.verbose, application.prelim_opts.output_file
+    prelim_opts, prelim_args = application.parse_preliminary_options_and_args(
+        []
     )
+    flake8.configure_logging(prelim_opts.verbose, prelim_opts.output_file)
     application.make_config_finder()
     application.find_plugins()
     application.register_plugin_options()

src/flake8/main/application.py

@@ -357,10 +357,10 @@ class Application(object):
         """
         # NOTE(sigmavirus24): When updating this, make sure you also update
         # our legacy API calls to these same methods.
-        self.parse_preliminary_options_and_args(argv)
-        flake8.configure_logging(
-            self.prelim_opts.verbose, self.prelim_opts.output_file
+        prelim_opts, prelim_args = self.parse_preliminary_options_and_args(
+            argv
         )
+        flake8.configure_logging(prelim_opts.verbose, prelim_opts.output_file)
         self.make_config_finder()
         self.find_plugins()
         self.register_plugin_options()

tests/unit/test_legacy_api.py

@@ -1,4 +1,6 @@
 """Tests for Flake8's legacy API."""
+import argparse
+
 import mock
 import pytest
 
@@ -8,9 +10,16 @@ from flake8.formatting import base as formatter
 
 def test_get_style_guide():
     """Verify the methods called on our internal Application."""
+    prelim_opts = argparse.Namespace(
+        output_file=None,
+        verbose=0,
+    )
     mockedapp = mock.Mock()
-    mockedapp.prelim_opts.verbose = 0
-    mockedapp.prelim_opts.output_file = None
+    mockedapp.prelim_opts = prelim_opts
+    mockedapp.parse_preliminary_options_and_args.return_value = (
+        prelim_opts,
+        [],
+    )
     with mock.patch('flake8.main.application.Application') as application:
         application.return_value = mockedapp
         style_guide = api.get_style_guide()