Python: fix: resolve string annotations in FunctionExecutor

[madebygps]

Enhance type hint validation in FunctionExecutor by importing typing and using get_type_hints to correctly resolve annotations.

This fixes validation failures when from __future__ import annotations is enabled, which stores annotations as strings.

Fixes #1808

Motivation and Context

This change is required to support Python codebases that use from __future__ import annotations (PEP 563).

1. Why is this change required?
   When from __future__ import annotations is enabled, type annotations are stored as strings rather than type objects. The current implementation of FunctionExecutor inspects param.annotation directly, which fails when it encounters a string (e.g., "WorkflowContext[str]") instead of the actual type object.

2. What problem does it solve?
   It solves the ValueError that occurs during FunctionExecutor initialization when users enable future annotations. The error looks like this:

   ValueError: Function instance parameter 'ctx' must be annotated as WorkflowContext, WorkflowContext[T], or WorkflowContext[T, U], got WorkflowContext
   

3. What scenario does it contribute to?
   It enables developers to use modern Python typing practices (PEP 563) and forward references within their agent workflows without runtime errors.

4. Issue Link: Fixes Python: Type checking fails for WorkflowContext annotation with from __future__ import annotations in Python 3.14 #1808

Description

The fix involves updating _validate_function_signature in _function_executor.py to correctly resolve type hints.

• Approach: Instead of relying solely on inspect.signature(...).parameters[...].annotation, I now use typing.get_type_hints(func) to resolve the annotations into their actual type objects.
• Implementation:
  • Imported typing.
  • Added type_hints = typing.get_type_hints(func) inside _validate_function_signature.
  • Updated the logic to retrieve both the message and ctx parameter annotations from the resolved type_hints dictionary.
  • Added a new test file test_function_executor_future.py that explicitly uses from __future__ import annotations to verify the fix and prevent regression.

Contribution Checklist

• The code builds clean without any errors or warnings
• The PR follows the Contribution Guidelines
• All unit tests pass, and I have added new tests where possible
• Is this a breaking change? No

[Copilot]

Pull Request Overview

This PR fixes type hint validation in FunctionExecutor to support Python's from __future__ import annotations (PEP 563), which stores type annotations as strings rather than type objects.

Key Changes:

• Updates _validate_function_signature to use typing.get_type_hints() for resolving string annotations to actual type objects
• Adds comprehensive test coverage for future annotations with both simple and complex type hints

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
python/packages/core/agent_framework/_workflows/_function_executor.py	Imports typing module and modifies signature validation to resolve stringified annotations using get_type_hints()
python/packages/core/tests/workflow/test_function_executor_future.py	Adds new test suite with from __future__ import annotations to verify the fix works with stringified type hints

[markwallace-microsoft]

Python Test Coverage Report •

File	Stmts	Miss	Cover	Missing
packages/core/agent_framework/_workflows
_function_executor.py	59	4	93%	82, 88, 94, 111
TOTAL	14990	2207	85%

Python Unit Test Overview

Tests	Skipped	Failures	Errors	Time
2041	127 💤	0 ❌	0 🔥	40.904s ⏱️