Python: fix(declarative): treat omitted workflow inputs as blank in PowerFx

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

@@ -70,6 +70,27 @@
 
 
 _ENV_REFERENCE_RE = re.compile(r"\bEnv\.([A-Za-z_][A-Za-z0-9_]*)")
+_INPUT_REFERENCE_RE = re.compile(r"(?<![\w.])(?:inputs|Workflow\.Inputs)\.([A-Za-z_][A-Za-z0-9_]*)")
+
+
+def _bind_missing_input_references(formula: str, symbols: dict[str, Any]) -> dict[str, Any]:
+    """Expose inputs the formula references but the caller did not supply as blank.
+
+    PowerFx rejects ``inputs.name`` at compile time when ``name`` is not a field of the
+    inputs record, which turns the whole expression into ``None`` and defeats defaults
+    such as ``If(IsBlank(inputs.name), "World", inputs.name)``. Binding the missing
+    fields to blank only for this evaluation makes them behave like an explicit ``None``
+    input without changing the workflow state.
+    """
+    inputs = symbols.get("inputs")
+    if not isinstance(inputs, Mapping):
+        return symbols
+    input_values = cast(Mapping[str, Any], inputs)
+    missing = {name for name in _INPUT_REFERENCE_RE.findall(formula) if name not in input_values}
+    if not missing:
+        return symbols
+    bound_inputs: dict[str, Any] = {**input_values, **dict.fromkeys(sorted(missing))}
+    return {**symbols, "Workflow": {**symbols["Workflow"], "Inputs": bound_inputs}, "inputs": bound_inputs}
 
 
 @dataclass(frozen=True)
@@ -605,7 +626,7 @@ def eval(self, expression: str) -> Any:
                     f"Install dotnet and the powerfx package for full PowerFx support."
                 )
 
-            symbols = self._to_powerfx_symbols()
+            symbols = _bind_missing_input_references(formula, self._to_powerfx_symbols())
             # Use setlocale(category) query form so we can restore the exact prior value.
             # getlocale() returns a normalized tuple and is not always a lossless
             # round-trip for setlocale across platforms/locales.

python/packages/declarative/tests/test_powerfx_yaml_compatibility.py

@@ -104,6 +104,23 @@ async def test_if_with_isblank(self, mock_state):
         result = state.eval('=If(IsBlank(Workflow.Inputs.name), "World", Workflow.Inputs.name)')
         assert result == "Alice"
 
+    @pytest.mark.parametrize(
+        "expression",
+        [
+            '=If(IsBlank(inputs.name), "World", inputs.name)',
+            '=If(IsBlank(Workflow.Inputs.name), "World", Workflow.Inputs.name)',
+        ],
+    )
+    async def test_if_with_isblank_when_input_is_missing(self, mock_state, expression):
+        """Test that an input the caller did not supply is blank, so IsBlank defaults apply."""
+        state = DeclarativeWorkflowState(mock_state)
+        state.initialize({"other": 1})
+
+        assert state.eval(expression) == "World"
+        assert state.eval("=IsBlank(inputs.name)") is True
+        # The missing input is only bound for evaluation, not written to state.
+        assert "name" not in state.get_state_data()["Inputs"]
+
     async def test_not_function(self, mock_state):
         """Test Not function."""
         state = DeclarativeWorkflowState(mock_state)

python/samples/03-workflows/declarative/simple_workflow/main.py

@@ -25,6 +25,8 @@ async def main() -> None:
     # Run with a custom name
     print("\nRunning with custom name 'Alice':")
     result = await workflow.run({"name": "Alice"})
+    for output in result.get_outputs():
+        print(f"  Output: {output}")
     print("\n" + "-" * 40)
     print("Workflow completed!")