increase task_class input validation and log messages and add unit test

src/workflow_app/workflow/states.py

@@ -9,8 +9,12 @@
 from .settings import POSTPROCESS_ERROR, CATALOG_DATA_READY
 from .settings import REDUCTION_DATA_READY, REDUCTION_CATALOG_DATA_READY
 from .database import transactions
+
+import importlib
+import inspect
 import json
 import logging
+import re
 
 
 class StateAction:
@@ -47,6 +51,30 @@ def _call_default_task(self, headers, message):
             action_cls = globals()[destination]
             action_cls(connection=self._send_connection)(headers, message)
 
+    def _get_class_from_path(self, class_path: str):
+        """
+        Returns the class given by the class path
+        :param class_path: the class, e.g. "module_name.ClassName"
+        :return: class or None
+        """
+        # check that the string is in the format "package_name.module_name.class_name"
+        pattern = r"^[a-zA-Z0-9_\.]+\.[a-zA-Z0-9_]+$"
+        if not re.match(pattern, class_path):
+            logging.error(f"task_class {class_path} does not match pattern module_name.ClassName")
+            return None
+        module_name, class_name = class_path.rsplit(".", 1)
+
+        # try importing the class
+        try:
+            module = importlib.import_module(module_name)
+            cls = getattr(module, class_name)
+            if not inspect.isclass(cls):
+                raise ValueError
+            return cls
+        except (ModuleNotFoundError, AttributeError, ValueError):
+            logging.error(f"task_class {class_path} cannot be imported")
+            return None
+
     def _call_db_task(self, task_data, headers, message):
         """
         :param task_data: JSON-encoded task definition
@@ -59,14 +87,12 @@ def _call_db_task(self, task_data, headers, message):
             and (task_def["task_class"] is not None)
             and len(task_def["task_class"].strip()) > 0
         ):
-            try:
-                toks = task_def["task_class"].strip().split(".")
-                module = ".".join(toks[: len(toks) - 1])
-                cls = toks[len(toks) - 1]
-                exec("from %s import %s as action_cls" % (module, cls))
-                action_cls(connection=self._send_connection)(headers, message)  # noqa: F821
-            except:  # noqa: E722
-                logging.exception("Task [%s] failed:", headers["destination"])
+            action_cls = self._get_class_from_path(task_def["task_class"])
+            if action_cls:
+                try:
+                    action_cls(connection=self._send_connection)(headers, message)  # noqa: F821
+                except:  # noqa: E722
+                    logging.exception("Task [%s] failed:", headers["destination"])
         if "task_queues" in task_def:
             for item in task_def["task_queues"]:
                 destination = "/queue/%s" % item

src/workflow_app/workflow/tests/test_states.py

@@ -6,7 +6,20 @@
 _ = [workflow]
 
 
+class FakeTestClass:
+    def __init__(self, connection):
+        pass
+
+    def __call__(self, headers, message):
+        raise ValueError
+
+
 class StateActionTest(TestCase):
+
+    @pytest.fixture(autouse=True)
+    def inject_fixtures(self, caplog):
+        self.caplog = caplog
+
     def test_call_default_task(self):
         from workflow.states import StateAction
 
@@ -47,6 +60,57 @@ def test_call(self, mock_get_task):
         sa(headers, message)
         assert mock_connection.send.call_count - original_call_count == 2  # one per task queue
 
+    @mock.patch("workflow.states.transactions.get_task")
+    def test_task_class_path(self, mock_get_task):
+        from workflow.states import StateAction
+
+        mock_connection = mock.Mock()
+        sa = StateAction(connection=mock_connection, use_db_task=True)
+        headers = {"destination": "test", "message-id": "test-0"}
+        message = '{"facility": "SNS", "instrument": "arcs", "ipts": "IPTS-5", "run_number": 3, "data_file": "test"}'
+
+        # test with task class "-" (inserted by Django admin interface when left empty)
+        mock_get_task.return_value = '{"task_class": "-"}'
+        self.caplog.clear()
+        sa(headers, message)
+        assert "does not match pattern" in self.caplog.text
+
+        # test with task class that does not follow the pattern "module_name.ClassName"
+        mock_get_task.return_value = '{"task_class": "FakeClass"}'
+        self.caplog.clear()
+        sa(headers, message)
+        assert "does not match pattern" in self.caplog.text
+
+        # test with module that does not exist
+        mock_get_task.return_value = '{"task_class": "fake_module.FakeClass"}'
+        self.caplog.clear()
+        sa(headers, message)
+        assert "cannot be imported" in self.caplog.text
+
+        # test with module exists but class does not
+        mock_get_task.return_value = '{"task_class": "workflow.states.FakeClass"}'
+        self.caplog.clear()
+        sa(headers, message)
+        assert "cannot be imported" in self.caplog.text
+
+        # test with module attribute is not a class
+        mock_get_task.return_value = '{"task_class": "workflow.state_utilities.decode_message"}'
+        self.caplog.clear()
+        sa(headers, message)
+        assert "cannot be imported" in self.caplog.text
+
+        # test with calling class fails
+        mock_get_task.return_value = '{"task_class": "workflow.tests.test_states.FakeTestClass"}'
+        self.caplog.clear()
+        sa(headers, message)
+        assert "Task [test] failed" in self.caplog.text
+
+        # test with valid class
+        mock_get_task.return_value = '{"task_class": "workflow.states.Reduction_request"}'
+        self.caplog.clear()
+        sa(headers, message)
+        assert mock_connection.send.call_count == 1
+
     @mock.patch("workflow.database.transactions.add_status_entry")
     def test_send(self, mockAddStatusEntry):
         from workflow.states import StateAction