Add support for local (in-repo, non-setuptools) plugins.

Closes #357

tests/integration/test_aggregator.py

@@ -5,6 +5,7 @@ import pytest
 
 from flake8.main import options
 from flake8.options import aggregator
+from flake8.options import config
 from flake8.options import manager
 
 CLI_SPECIFIED_CONFIG = 'tests/fixtures/config_files/cli-specified.ini'
@@ -25,7 +26,9 @@ def test_aggregate_options_with_config(optmanager):
     """Verify we aggregate options and config values appropriately."""
     arguments = ['flake8', '--config', CLI_SPECIFIED_CONFIG, '--select',
                  'E11,E34,E402,W,F', '--exclude', 'tests/*']
-    options, args = aggregator.aggregate_options(optmanager, arguments)
+    config_finder = config.ConfigFileFinder('flake8', arguments, [])
+    options, args = aggregator.aggregate_options(
+        optmanager, config_finder, arguments)
 
     assert options.config == CLI_SPECIFIED_CONFIG
     assert options.select == ['E11', 'E34', 'E402', 'W', 'F']
@@ -37,8 +40,10 @@ def test_aggregate_options_when_isolated(optmanager):
     """Verify we aggregate options and config values appropriately."""
     arguments = ['flake8', '--isolated', '--select', 'E11,E34,E402,W,F',
                  '--exclude', 'tests/*']
+    config_finder = config.ConfigFileFinder('flake8', arguments, [])
     optmanager.extend_default_ignore(['E8'])
-    options, args = aggregator.aggregate_options(optmanager, arguments)
+    options, args = aggregator.aggregate_options(
+        optmanager, config_finder, arguments)
 
     assert options.isolated is True
     assert options.select == ['E11', 'E34', 'E402', 'W', 'F']

tests/integration/test_plugins.py

@@ -0,0 +1,58 @@
+"""Integration tests for plugin loading."""
+from flake8.main import application
+
+
+LOCAL_PLUGIN_CONFIG = 'tests/fixtures/config_files/local-plugin.ini'
+
+
+class ExtensionTestPlugin(object):
+    """Extension test plugin."""
+
+    name = 'ExtensionTestPlugin'
+    version = '1.0.0'
+
+    def __init__(self, tree):
+        """Construct an instance of test plugin."""
+        pass
+
+    def run(self):
+        """Do nothing."""
+        pass
+
+    @classmethod
+    def add_options(cls, parser):
+        """Register options."""
+        parser.add_option('--anopt')
+
+
+class ReportTestPlugin(object):
+    """Report test plugin."""
+
+    name = 'ReportTestPlugin'
+    version = '1.0.0'
+
+    def __init__(self, tree):
+        """Construct an instance of test plugin."""
+        pass
+
+    def run(self):
+        """Do nothing."""
+        pass
+
+
+def test_enable_local_plugin_from_config():
+    """App can load a local plugin from config file."""
+    app = application.Application()
+    app.initialize(['flake8', '--config', LOCAL_PLUGIN_CONFIG])
+
+    assert app.check_plugins['XE'].plugin is ExtensionTestPlugin
+    assert app.formatting_plugins['XR'].plugin is ReportTestPlugin
+
+
+def test_local_plugin_can_add_option():
+    """A local plugin can add a CLI option."""
+    app = application.Application()
+    app.initialize(
+        ['flake8', '--config', LOCAL_PLUGIN_CONFIG, '--anopt', 'foo'])
+
+    assert app.options.anopt == 'foo'