Utilize IServiceProviderIsService in AIFunctionFactory

[stephentoub]

Add AIFunctionFactoryOptions.Services, and use it when examining function parameters to determine whether they should be resolved by default from DI.

Closes #6312, whether or not we decide to merge this.

Microsoft Reviewers: Open in CodeFlow

[jeffhandley]

I'm in favor of supporting this.

Do I understand correctly though that the potential drawback is that we take the liberty of excluding parameters that will be resolved from the service provider from the schema exchanged with the model, therefore preventing the model from being able to include a value for the parameter itself, and there might be scenarios where that would be unexpected/undesired?

After typing that, I asked Copilot what the potential drawbacks were, and it included that reasoning and also included other drawbacks, pasted below.

I'm still in favor myself though, and the implementation plugs in very surgically, so I'm comfortable with the risk at this stage too, but this could also be serviced in later as a behavioral breaking change that I think would be acceptable.

I ultimately defer to you two though, @stephentoub and @SteveSandersonMS.

The potential drawback in integrating the feature outlined in this pull request includes:

1. Increased Complexity:

   • The addition of IServiceProvider-specific logic introduces more complexity to the AIFunctionFactory and its associated classes. This could make the code harder to understand, maintain, and debug, especially for developers unfamiliar with the dependency injection flow.

2. Dependency on IServiceProvider:

   • Tight coupling with IServiceProvider and IServiceProviderIsService may make the feature less flexible. This dependency assumes that the IServiceProvider provided at construction matches the one used during invocation, which could lead to issues if mismatched.

3. Behavioral Changes:

   • Parameters that can be resolved via IServiceProvider are excluded from the JSON schema. This change in behavior may surprise users who expect all parameters to be explicitly listed in the schema. It may also create discrepancies between the schema and runtime behavior.

4. Error Handling Overhead:

   • The feature introduces additional error handling for cases where IServiceProvider is missing or fails to resolve a parameter. This might lead to more runtime exceptions, adding to the risk of failure if users do not carefully configure the Services.

5. Testing Complexity:

   • Unit testing becomes more challenging because the behavior of the functions now depends on external services and their availability in the provided IServiceProvider. Mocking or setting up these services for tests could increase the burden on test authors.

6. Potential for Misconfiguration:

   • If the Services provided during construction and invocation are not aligned or do not satisfy the required dependencies, the feature could fail at runtime. This may make it harder for developers to debug and resolve configuration issues.

7. Backward Compatibility:

   • Existing users of the library who rely on the explicit schema for all parameters or who do not use IServiceProvider may need to adjust their code to accommodate the new behavior.

8. Performance Overhead:

   • Resolving parameters dynamically from IServiceProvider may introduce slight performance overhead compared to binding all parameters from the arguments dictionary.

These drawbacks should be weighed against the benefits of making the library more dependency-injection-friendly and flexible for users relying on service resolution.