fix(dspy): fix null reference in settings.trace

[grant-d]

Using dspy-ai===2.4.5
When using the following code:

__llm = dspy.Google(model="models/gemini-1.5-flash")
dspy.settings.configure(lm=__llm) # error below!
dspy.settings.configure(lm=__llm, trace=[]) # mitigates error (but NOT the fix)

# __llm = dspy.OpenAI(model="gpt-4o") # Works fine


class PlannerModule(dspy.Module):
  def forward(self, ...):
    # ... trivial implementation ...
    dspy.Suggest(...)

exec = PlannerModule().activate_assertions(max_backtracks=3)
prediction: dspy.Prediction = exec(input)

I get the following error:

Traceback (most recent call last):
  File "...xyz.py", line 91, in <module>
    prediction: dspy.Prediction = exec(input)
                                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Volumes/Data/repos/jigxie/.venv/lib/python3.12/site-packages/dspy/primitives/program.py", line 26, in __call__
    return self.forward(*args, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Volumes/Data/repos/jigxie/.venv/lib/python3.12/site-packages/dspy/primitives/assertions.py", line 318, in forward
    return wrapped_forward(*args, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Volumes/Data/repos/jigxie/.venv/lib/python3.12/site-packages/dspy/primitives/assertions.py", line 241, in wrapper
    dsp.settings.trace.clear()
    ^^^^^^^^^^^^^^^^^^^^^^^^
AttributeError: 'NoneType' object has no attribute 'clear'

Not sure why there is a difference in behavior between OpenAI and Google, however, via visual inspection the fix is both defensive & trivial:

• Added a null-check per similar code elsewhere in the codebase.

[okhat]

Thank you @grant-d ! I'm not sure this is a correct fix. Why clear the trace altogether?

[okhat]

i.e., I agree we may need a correction or something but clearing seems not to be the fix?

[grant-d]

@okhat it was the simplest fix, I didn't have time to figure out the root cause in the Google provider.

[grant-d]

Oh wait. I think you misunderstood my fix. The clear() statement was already there (see diff), I just wrapped it in a null-check

[arnavsinghvi11]

Hi @grant-d , this is a chance actually only needed when using DSPy.assertions. Please refer to #528, #434

[grant-d]

I do agree that it only happens when using assertions. But in terms of defensive coding best-practices, why not add the null-check anyway?
It's not like the error message is a feature, it would seem to be a bug regardless?

[arnavsinghvi11]

took a deeper look and it seems like this fix is not the intended behavior as #620 actually covered setting trace to be initialized to an empty list on each configuration. while the suggested change adds a null-check (which we can merge), ideally, we do not want to force the user to manually set trace=[] to activate assertions. dspy.settings.configure(lm=__llm) should work as is since trace should default to [] anyways.

seems like the bug is actually in dspy.Google. I think it could be because of the defined self.config overriding self.config for settings and other use cases in DSPy. I don't have access to test this myself, but if you change that variable to another name and refactor dspy.Google accordingly, does this resolve the error and work with dspy.settings.configure(lm=__llm) as is.