added tests to test Python functions with no outputs

Author: tclose

pydra/compose/base/helpers.py

@@ -183,7 +183,7 @@ def extract_function_inputs_and_outputs(
         input_types[p.name] = type_hints.get(p.name, ty.Any)
         if p.default is not inspect.Parameter.empty:
             input_defaults[p.name] = p.default
-    if inputs:
+    if inputs is not None:
         if not isinstance(inputs, dict):
             raise ValueError(
                 f"Input names ({inputs}) should not be provided when "
@@ -218,45 +218,46 @@ def extract_function_inputs_and_outputs(
                 f"value {default}"
             )
     return_type = type_hints.get("return", ty.Any)
-    if outputs and len(outputs) > 1:
-        if return_type is not ty.Any:
-            if ty.get_origin(return_type) is not tuple:
-                raise ValueError(
-                    f"Multiple outputs specified ({outputs}) but non-tuple "
-                    f"return value {return_type}"
-                )
-            return_types = ty.get_args(return_type)
-            if len(return_types) != len(outputs):
-                raise ValueError(
-                    f"Length of the outputs ({outputs}) does not match that "
-                    f"of the return types ({return_types})"
-                )
-            output_types = dict(zip(outputs, return_types))
-        else:
-            output_types = {o: ty.Any for o in outputs}
-        if isinstance(outputs, dict):
-            for output_name, output in outputs.items():
-                if isinstance(output, Out) and output.type is ty.Any:
-                    output.type = output_types[output_name]
+    if outputs:
+        if len(outputs) > 1:
+            if return_type is not ty.Any:
+                if ty.get_origin(return_type) is not tuple:
+                    raise ValueError(
+                        f"Multiple outputs specified ({outputs}) but non-tuple "
+                        f"return value {return_type}"
+                    )
+                return_types = ty.get_args(return_type)
+                if len(return_types) != len(outputs):
+                    raise ValueError(
+                        f"Length of the outputs ({outputs}) does not match that "
+                        f"of the return types ({return_types})"
+                    )
+                output_types = dict(zip(outputs, return_types))
+            else:
+                output_types = {o: ty.Any for o in outputs}
+            if isinstance(outputs, dict):
+                for output_name, output in outputs.items():
+                    if isinstance(output, Out) and output.type is ty.Any:
+                        output.type = output_types[output_name]
+            else:
+                outputs = output_types
         else:
-            outputs = output_types
-
-    elif outputs:
-        if isinstance(outputs, dict):
-            output_name, output = next(iter(outputs.items()))
-        elif isinstance(outputs, list):
-            output_name = outputs[0]
-            output = ty.Any
-        if isinstance(output, Out):
-            if output.type is ty.Any:
-                output.type = return_type
-        elif output is ty.Any:
-            output = return_type
-        outputs = {output_name: output}
-    elif return_type is not None:
-        outputs = {"out": return_type}
+            if isinstance(outputs, dict):
+                output_name, output = next(iter(outputs.items()))
+            elif isinstance(outputs, list):
+                output_name = outputs[0]
+                output = ty.Any
+            if isinstance(output, Out):
+                if output.type is ty.Any:
+                    output.type = return_type
+            elif output is ty.Any:
+                output = return_type
+            outputs = {output_name: output}
     else:
-        outputs = {}
+        if return_type not in (None, type(None)):
+            outputs = {"out": return_type}
+        else:
+            outputs = {}
     return inputs, outputs
 
 

pydra/compose/tests/test_python_fields.py

@@ -424,3 +424,38 @@ def TestFunc(a: A):
 
     outputs = TestFunc(a=A(x=7))()
     assert outputs.out == 7
+
+
+def test_no_outputs1():
+    """Test function tasks with object inputs"""
+
+    @python.define
+    def TestFunc(a: A) -> None:
+        pass
+
+    outputs = TestFunc(a=A(x=7))()
+    assert len(outputs) == 0
+
+
+def test_no_outputs2():
+    """Test function tasks with object inputs"""
+
+    @python.define(outputs=[])
+    def TestFunc(a: A):
+        pass
+
+    outputs = TestFunc(a=A(x=7))()
+    assert len(outputs) == 0
+
+
+def test_no_outputs_fail():
+    """Test function tasks with object inputs"""
+
+    @python.define(outputs=[])
+    def TestFunc(a: A):
+        return a
+
+    with pytest.raises(
+        ValueError, match="Returns an output but no outputs are defined"
+    ):
+        TestFunc(a=A(x=7))()