Correctly merge Model.settings with model_settings in direct mode

[moritzwilksch]

fixes #2956

by merging the Model.settings with the provided model_settings within each model's request method. In an earlier version I adjusted only the direct functions in direct.py but since users can use my_model.request(...) as well, the merging should be the responsibility of the Model.

[moritzwilksch]

@DouweM Do you have any suggestions on how to test this?

[DouweM]

@moritzwilksch Might it be easier to do this in pydantic_ai.direct.model_request, analogous to how we do it in Agent.iter?

pydantic-ai/pydantic_ai_slim/pydantic_ai/agent/__init__.py

Lines 591 to 592 in bfcccba

	merged_settings = merge_model_settings(model_used.settings, self.model_settings)
	model_settings = merge_model_settings(merged_settings, model_settings)

You could test it using FunctionModel like in this test:

pydantic-ai/tests/models/test_model_settings.py

Line 74 in bfcccba

def test_settings_merge_hierarchy():

[moritzwilksch]

I implemented it there initially but users can also invoke Model.request and would expect the settings to be respected, right?

[DouweM]

@moritzwilksch Hmm, that's right, but then I think we should do the same thing for customize_request_parameters, which is not currently called by the models themselves either, just the model.request call sites in the agent graph and direct. I don't love putting those two calls in all the model request methods, though.

I'd prefer just one repeated line:

model_settings, model_request_parameters = self.prepare_request(model_settings, model_request_parameters)

Can you implement that on Model to call the merge_model_settings and customize_request_parameters methods and explain in the docstring that it can be overwritten (as the customize_request_parameters docstring says currently)? Then we can also remove the explicit customize_request_parameters calls.

[moritzwilksch]

thanks for the pointers, changed. Let me know whether this is missing anything

[DouweM]

@moritzwilksch Thanks Moritz!