ZeroDivisionError in determine_intent when tags are empty

[PLNech]

• I'm using an IntentDeterminationEngine along the lines of the Multi Intent parser Example, with no required entity type and several optional ones.

Stacktrace

  File "/home/pln/.PyCharm2019.3/config/scratches/scratch_12.py", line 16, in <module>
    print([i for i in engine.determine_intent(utterance, include_tags=False)])
  File "/home/pln/.PyCharm2019.3/config/scratches/scratch_12.py", line 16, in <listcomp>
    print([i for i in engine.determine_intent(utterance, include_tags=False)])
  File "/home/pln/.virtualenvs/nluservice/src/adapt-parser/adapt/engine.py", line 131, in determine_intent
    best_intent, tags = self.__best_intent(result, remaining_context)
  File "/home/pln/.virtualenvs/nluservice/src/adapt-parser/adapt/engine.py", line 81, in __best_intent
    i, tags = intent.validate_with_tags(parse_result.get('tags') + context_as_entities, parse_result.get('confidence'))
  File "/home/pln/.virtualenvs/nluservice/src/adapt-parser/adapt/intent.py", line 190, in validate_with_tags
    total_confidence = intent_confidence / len(tags) * confidence
ZeroDivisionError: float division by zero

Steps to replicate the Issue

1. Define an IntentDeterminationEngine as such:

    engine: IntentDeterminationEngine = IntentDeterminationEngine()
    engine.register_entity("Kevin", "who") # same problem if several entities
    builder: IntentBuilder = IntentBuilder("Buddies")
    builder.optionally("who") # same problem if several entity types
    engine.register_intent_parser(builder.build())

2. Use it on an utterance that contains an entity, get expected results

print([i for i in engine.determine_intent("Kevin is a friend")]) # works

3. Use it on an utterance that contains no entity, get an exception

print([i for i in engine.determine_intent("Julien is a friend")]) # raises

Can also be reproduced with an empty utterance "".

Be as specific as possible about the expected condition, and the deviation from expected condition.

I expect the engine to return an empty determination ([]) when no entity is recognized, instead of raising a generic ZeroDivisionError exception.

[PLNech]

I believe fixing this could just mean refactoring validate_with_tags. For now I'd see this as:

• Update the line 190 that divides by the length of a potentially empty collection:
  

  adapt/adapt/intent.py

  Line 190 in 402d2d8

  total_confidence = intent_confidence / len(tags) * confidence

  • Could be wrapped in a conditional, e.g. total_confidence = [..] or 0 if not tags

• Take the opportunity to clarify the role of the confidence parameter, documented as a float:
  

  adapt/adapt/intent.py

  Lines 137 to 142 in 402d2d8

  	def validate_with_tags(self, tags, confidence):
  	"""Validate whether tags has required entites for this intent to fire
  	Args:
  	tags(list): Tags and Entities used for validation
  	confidence(float): ?

  From my understanding, its value is always ignored, being redefined here:

  adapt/adapt/intent.py

  Line 155 in 402d2d8

  required_tag, canonical_form, confidence = find_first_tag(local_tags, require_type)

  Its final value is used to compute the total confidence in the line 190 I linked above. Thus, the new value of confidence defined line 192 is never used:
  

  adapt/adapt/intent.py

  Line 192 in 402d2d8

  target_client, canonical_form, confidence = find_first_tag(local_tags, CLIENT_ENTITY_NAME)

  • Could remove confidence from validate_with_tags's parameters as it is never used
  • Could replace confidence by _ in line 192 as it is never used