catching any command generator exceptions

rasa/cdu/generator/command_generator.py

@@ -1,10 +1,13 @@
 from typing import List, Optional
+import structlog
 from rasa.cdu.commands import Command
 from rasa.shared.core.flows.flow import FlowsList
 from rasa.shared.core.trackers import DialogueStateTracker
 from rasa.shared.nlu.training_data.message import Message
 from rasa.shared.nlu.constants import COMMANDS
 
+structlogger = structlog.get_logger()
+
 
 class CommandGenerator:
     """A command generator.
@@ -33,7 +36,13 @@ def process(
         The processed messages (usually this is just one during prediction).
         """
         for message in messages:
-            commands = self.predict_commands(message, flows, tracker)
+            try:
+                commands = self.predict_commands(message, flows, tracker)
+            except Exception as e:
+                if isinstance(e, NotImplementedError):
+                    raise e
+                structlogger.error("command_generator.predict.error", error=e)
+                commands = []
             commands_dicts = [command.as_dict() for command in commands]
             message.set(COMMANDS, commands_dicts, add_to_output=True)
         return messages

tests/cdu/generator/test_command_generator.py

@@ -0,0 +1,42 @@
+from typing import Optional, List
+
+import pytest
+
+from rasa.cdu.commands import Command
+from rasa.cdu.generator.command_generator import CommandGenerator
+from rasa.cdu.commands.chit_chat_answer_command import ChitChatAnswerCommand
+from rasa.shared.core.flows.flow import FlowsList
+from rasa.shared.core.trackers import DialogueStateTracker
+from rasa.shared.nlu.constants import TEXT, COMMANDS
+from rasa.shared.nlu.training_data.message import Message
+
+
+class WackyCommandGenerator(CommandGenerator):
+    def predict_commands(
+        self,
+        message: Message,
+        flows: FlowsList,
+        tracker: Optional[DialogueStateTracker] = None,
+    ) -> List[Command]:
+        if message.get(TEXT) == "Hi":
+            raise ValueError("Message too banal - I am quitting.")
+        else:
+            return [ChitChatAnswerCommand()]
+
+
+def test_command_generator_catches_processing_errors():
+    generator = WackyCommandGenerator()
+    messages = [Message.build("Hi"), Message.build("What is your purpose?")]
+    generator.process(messages, FlowsList([]))
+    commands = [m.get(COMMANDS) for m in messages]
+
+    assert len(commands[0]) == 0
+    assert len(commands[1]) == 1
+    assert commands[1][0]["command"] == ChitChatAnswerCommand.command()
+
+
+def test_command_generator_still_throws_not_implemented_error():
+    # This test can be removed if the predict_commands method stops to be abstract
+    generator = CommandGenerator()
+    with pytest.raises(NotImplementedError):
+        generator.process([Message.build("test")], FlowsList([]))