Merge branch 'main' into copilot/fix-conditional-powerfx-import

Co-authored-by: markwallace-microsoft <127216156+markwallace-microsoft@users.noreply.github.com>

python/packages/declarative/agent_framework_declarative/_workflows/_declarative_base.py

@@ -30,14 +30,22 @@ import sys
 from collections.abc import Mapping
 from dataclasses import dataclass
 from decimal import Decimal as _Decimal
-from typing import Any, Literal, cast
+from typing import TYPE_CHECKING, Any, Literal, cast
 
 from agent_framework._workflows import (
     Executor,
     WorkflowContext,
 )
 from agent_framework._workflows._state import State
-from powerfx import Engine
+
+try:
+    from powerfx import Engine
+
+    _powerfx_available = True
+except (ImportError, RuntimeError):
+    _powerfx_available = False
+    if TYPE_CHECKING:
+        from powerfx import Engine  # type: ignore[assignment]
 
 if sys.version_info >= (3, 11):
     from typing import TypedDict  # type: ignore # pragma: no cover
@@ -363,6 +371,14 @@ class DeclarativeWorkflowState:
         # Replace them with their evaluated results before sending to PowerFx
         formula = self._preprocess_custom_functions(formula)
 
+        # Check if powerfx is available
+        if not _powerfx_available:
+            raise ImportError(
+                "The 'powerfx' package is required to evaluate PowerFx expressions. "
+                "Please install .NET and the 'powerfx' package to use PowerFx expressions. "
+                "See https://github.com/microsoft/agent-framework for installation instructions."
+            )
+
         engine = Engine()
         symbols = self._to_powerfx_symbols()
         try: