Ensure exceptions are pickleable

tests/unit/test_exceptions.py

@@ -0,0 +1,54 @@
+"""Tests for the flake8.exceptions module."""
+import pickle
+
+import entrypoints
+
+from flake8 import exceptions
+from flake8.plugins import manager as plugins_manager
+
+
+class _ExceptionTest:
+    def test_pickleable(self):
+        """Test that the exception is round-trip pickleable."""
+        for proto in range(pickle.HIGHEST_PROTOCOL + 1):
+            new_err = pickle.loads(pickle.dumps(self.err, protocol=proto))
+            assert str(self.err) == str(new_err)
+            orig_e = self.err.original_exception
+            new_e = new_err.original_exception
+            assert (type(orig_e), orig_e.args) == (type(new_e), new_e.args)
+
+
+class TestFailedToLoadPlugin(_ExceptionTest):
+    """Tests for the FailedToLoadPlugin exception."""
+
+    err = exceptions.FailedToLoadPlugin(
+        plugin=plugins_manager.Plugin(
+            'plugin_name',
+            entrypoints.EntryPoint('plugin_name', 'os.path', None),
+        ),
+        exception=ValueError('boom!'),
+    )
+
+
+class TestInvalidSyntax(_ExceptionTest):
+    """Tests for the InvalidSyntax exception."""
+
+    err = exceptions.InvalidSyntax(exception=ValueError('Unexpected token: $'))
+
+
+class TestPluginRequestedUnknownParameters(_ExceptionTest):
+    """Tests for the PluginRequestedUnknownParameters exception."""
+
+    err = exceptions.PluginRequestedUnknownParameters(
+        plugin={'plugin_name': 'plugin_name'},
+        exception=ValueError('boom!'),
+    )
+
+
+class TestPluginExecutionFailed(_ExceptionTest):
+    """Tests for the PluginExecutionFailed exception."""
+
+    err = exceptions.PluginExecutionFailed(
+        plugin={'plugin_name': 'plugin_name'},
+        exception=ValueError('boom!'),
+    )