Merge branch 'bug/320' into 'master'

Handle older versions of setuptools than we expect

Closes #320

See merge request !182

setup.py

@@ -20,6 +20,7 @@ requires = [
     "pyflakes >= 1.5.0, < 1.6.0",
     "pycodestyle >= 2.0.0, < 2.4.0",
     "mccabe >= 0.6.0, < 0.7.0",
+    "setuptools >= 30",
 ]
 
 if sys.version_info < (3, 4):

src/flake8/exceptions.py

@@ -13,6 +13,10 @@ class EarlyQuit(Flake8Exception):
     pass
 
 
+class ExecutionError(Flake8Exception):
+    """Exception raised during execution of Flake8."""
+
+
 class FailedToLoadPlugin(Flake8Exception):
     """Exception raised when a plugin fails to load."""
 

src/flake8/main/application.py

@@ -185,6 +185,28 @@ class Application(object):
                                                 self.options,
                                                 self.args)
 
+    def formatter_for(self, formatter_plugin_name):
+        """Retrieve the formatter class by plugin name."""
+        try:
+            default_formatter = self.formatting_plugins['default']
+        except KeyError:
+            raise exceptions.ExecutionError(
+                "The 'default' Flake8 formatting plugin is unavailable. "
+                "This usually indicates that your setuptools is too old. "
+                "Please upgrade setuptools. If that does not fix the issue"
+                " please file an issue."
+            )
+
+        formatter_plugin = self.formatting_plugins.get(formatter_plugin_name)
+        if formatter_plugin is None:
+            LOG.warning(
+                '"%s" is an unknown formatter. Falling back to default.',
+                formatter_plugin_name,
+            )
+            formatter_plugin = default_formatter
+
+        return formatter_plugin.execute
+
     def make_formatter(self, formatter_class=None):
         # type: () -> NoneType
         """Initialize a formatter based on the parsed options."""
@@ -196,9 +218,7 @@ class Application(object):
                 format_plugin = 'quiet-nothing'
 
             if formatter_class is None:
-                formatter_class = self.formatting_plugins.get(
-                    format_plugin, self.formatting_plugins['default']
-                ).execute
+                formatter_class = self.formatter_for(format_plugin)
 
             self.formatter = formatter_class(self.options)
 
@@ -332,6 +352,11 @@ class Application(object):
             LOG.exception(exc)
             self.file_checker_manager._force_cleanup()
             self.catastrophic_failure = True
+        except exceptions.ExecutionError as exc:
+            print('There was a critical error during execution of Flake8:')
+            print(exc.message)
+            LOG.exception(exc)
+            self.catastrophic_failure = True
         except exceptions.EarlyQuit:
             self.catastrophic_failure = True
             print('... stopped while processing files')

tests/unit/test_application.py

@@ -4,6 +4,7 @@ import optparse
 import mock
 import pytest
 
+from flake8 import exceptions
 from flake8.main import application as app
 
 
@@ -16,6 +17,17 @@ def options(**kwargs):
     return optparse.Values(kwargs)
 
 
+@pytest.fixture
+def mocked_application():
+    """Create an application with a mocked OptionManager."""
+    with mock.patch('flake8.options.manager.OptionManager') as optionmanager:
+        optmgr = optionmanager.return_value = mock.Mock()
+        optmgr.parse_known_args.return_value = (options(), [])
+        application = app.Application()
+
+    return application
+
+
 @pytest.mark.parametrize(
     'result_count, catastrophic, exit_zero', [
         (0, True, True),
@@ -23,18 +35,14 @@ def options(**kwargs):
         (2, True, True),
     ]
 )
-def test_exit_does_not_raise(result_count, catastrophic, exit_zero):
+def test_exit_does_not_raise(result_count, catastrophic, exit_zero,
+                             mocked_application):
     """Verify Application.exit doesn't raise SystemExit."""
-    with mock.patch('flake8.options.manager.OptionManager') as optionmanager:
-        optmgr = optionmanager.return_value = mock.Mock()
-        optmgr.parse_known_args.return_value = (options(), [])
-        application = app.Application()
+    mocked_application.result_count = result_count
+    mocked_application.catastrophic_failure = catastrophic
+    mocked_application.options = options(exit_zero=exit_zero)
 
-    application.result_count = result_count
-    application.catastrophic_failure = catastrophic
-    application.options = options(exit_zero=exit_zero)
-
-    assert application.exit() is None
+    assert mocked_application.exit() is None
 
 
 @pytest.mark.parametrize(
@@ -45,18 +53,51 @@ def test_exit_does_not_raise(result_count, catastrophic, exit_zero):
         (2, True, False, True),
     ]
 )
-def test_exit_does_raise(result_count, catastrophic, exit_zero, value):
+def test_exit_does_raise(result_count, catastrophic, exit_zero, value,
+                         mocked_application):
     """Verify Application.exit doesn't raise SystemExit."""
-    with mock.patch('flake8.options.manager.OptionManager') as optionmanager:
-        optmgr = optionmanager.return_value = mock.Mock()
-        optmgr.parse_known_args.return_value = (options(), [])
-        application = app.Application()
-
-    application.result_count = result_count
-    application.catastrophic_failure = catastrophic
-    application.options = options(exit_zero=exit_zero)
+    mocked_application.result_count = result_count
+    mocked_application.catastrophic_failure = catastrophic
+    mocked_application.options = options(exit_zero=exit_zero)
 
     with pytest.raises(SystemExit) as excinfo:
-        application.exit()
+        mocked_application.exit()
 
     assert excinfo.value.args[0] is value
+
+
+def test_missing_default_formatter(mocked_application):
+    """Verify we raise an ExecutionError when there's no default formatter."""
+    mocked_application.formatting_plugins = {}
+
+    with pytest.raises(exceptions.ExecutionError):
+        mocked_application.formatter_for('fake-plugin-name')
+
+
+def test_warns_on_unknown_formatter_plugin_name(mocked_application):
+    """Verify we log a warning with an unfound plugin."""
+    default = mock.Mock()
+    execute = default.execute
+    mocked_application.formatting_plugins = {
+        'default': default,
+    }
+    with mock.patch.object(app.LOG, 'warning') as warning:
+        assert execute is mocked_application.formatter_for('fake-plugin-name')
+
+    assert warning.called is True
+    assert warning.call_count == 1
+
+
+def test_returns_specified_plugin(mocked_application):
+    """Verify we get the plugin we want."""
+    desired = mock.Mock()
+    execute = desired.execute
+    mocked_application.formatting_plugins = {
+        'default': mock.Mock(),
+        'desired': desired,
+    }
+
+    with mock.patch.object(app.LOG, 'warning') as warning:
+        assert execute is mocked_application.formatter_for('desired')
+
+    assert warning.called is False