fix: restrict missing component attributes to declared I/O fields

plugboard/component/component.py

@@ -211,9 +211,18 @@ def _get_component_bases(cls) -> list[_t.Type[Component]]:
 
     # Prevents type-checker errors on public component IO attributes
     def __getattr__(self, key: str) -> _t.Any:
+        """Return `None` for unset declared public I/O fields only.
+
+        Use the current controller so fields declared at runtime are supported.
+        An unset field is not added to the instance dictionary, distinguishing it
+        from a field explicitly assigned `None`.
+        """
         if not key.startswith("_"):
-            return None
-        raise AttributeError(f"'{self.__class__.__name__}' object has no attribute '{key}'")
+            io = object.__getattribute__(self, "io")
+            if key in io.inputs or key in io.outputs:
+                return None
+        name = object.__getattribute__(self, "__dict__").get("name", "<unnamed>")
+        raise AttributeError(f"{type(self).__name__} component '{name}' has no attribute '{key}'")
 
     def __setattr__(self, key: str, value: _t.Any) -> None:
         """Sets attributes on the component.
@@ -229,7 +238,12 @@ def __setattr__(self, key: str, value: _t.Any) -> None:
     @property
     def id(self) -> str:
         """Unique ID for `Component`."""
-        return self.name
+        try:
+            return self.name
+        except AttributeError as e:
+            raise ValidationError(
+                "Component invalid: did you forget to call super().__init__ in the constructor?"
+            ) from e
 
     @property
     def state(self) -> _t.Optional[StateBackend]:

tests/integration/test_process_validation.py

@@ -70,12 +70,11 @@ def __init__(*args: _t.Any, **kwargs: _t.Any) -> None:
         async def step(self) -> None:
             self.y = self.x
 
-    process = LocalProcess(
-        components=[A(name="a", iters=10), NoSuperCall(name="test-no-super")],
-        connectors=[
-            AsyncioConnector(spec=ConnectorSpec(source="a.out_1", target="test-no-super.x"))
-        ],
-    )
-
     with pytest.raises(exceptions.ValidationError, match="forget to call super"):
+        process = LocalProcess(
+            components=[A(name="a", iters=10), NoSuperCall(name="test-no-super")],
+            connectors=[
+                AsyncioConnector(spec=ConnectorSpec(source="a.out_1", target="test-no-super.x"))
+            ],
+        )
         await process.init()

tests/unit/test_component.py

@@ -1,12 +1,15 @@
 """Unit tests for `Component`."""
 # ruff: noqa: D101,D102,D103
 
+import copy
+from pathlib import Path
 import typing as _t
 
 import pytest
 
 from plugboard.component import Component, IOController as IO
 from plugboard.connector import AsyncioConnector
+from plugboard.library.file_io import FileReader, FileWriter
 from plugboard.schemas import ComponentArgsDict, ConnectorSpec, Status
 
 
@@ -34,6 +37,81 @@ async def step(self) -> None:
             await self.io.close()
 
 
+@pytest.mark.parametrize("field", ["a", "b", "c"])
+def test_unset_declared_field(field: str) -> None:
+    component = A(name="static")
+    assert getattr(component, field) is None
+    assert hasattr(component, field)
+    assert field not in vars(component)
+    assert component._field_inputs == {}
+    assert not component._field_inputs_ready
+
+    setattr(component, field, None)
+    assert getattr(component, field) is None
+    assert field in vars(component)
+    if field in component.io.inputs:
+        assert field in component._field_inputs
+
+
+@pytest.mark.parametrize("field", ["misspelled", "_missing", "__setstate__"])
+def test_unknown_attribute(field: str) -> None:
+    component = A(name="static")
+    with pytest.raises(AttributeError, match=f"A component 'static'.*'{field}'"):
+        getattr(component, field)
+    assert not hasattr(component, field)
+    assert getattr(component, field, "fallback") == "fallback"
+
+
+def test_normal_attributes_and_inherited_ports() -> None:
+    class Derived(A):
+        io = IO(outputs=["extra"])
+
+    component = Derived(name="derived")
+    component.custom = 42
+    assert component.name == "derived"
+    assert component.custom == 42
+    for field in ("a", "b", "c", "extra"):
+        assert getattr(component, field) is None
+
+
+def test_attribute_lookup_before_initialization() -> None:
+    component = object.__new__(A)
+    assert component.a is None
+    with pytest.raises(AttributeError, match="A component '<unnamed>'.*'missing'"):
+        component.missing
+
+
+def test_dynamic_reader_ports_are_instance_specific(tmp_path: Path) -> None:
+    reader = FileReader(name="reader", path=tmp_path / "data.csv", field_names=["temperature"])
+    other = FileReader(name="other", path=tmp_path / "data.csv", field_names=["pressure"])
+    assert reader.temperature is None
+    assert hasattr(reader, "temperature")
+    assert not hasattr(other, "temperature")
+    assert other.pressure is None
+    assert not hasattr(reader, "pressure")
+    with pytest.raises(AttributeError, match="FileReader component 'reader'.*'temprature'"):
+        reader.temprature
+
+    reader.temperature = 12
+    assert reader.temperature == 12
+    restored = FileReader(**reader.export()["args"])
+    assert restored.temperature is None
+    assert not hasattr(restored, "pressure")
+    cloned = copy.deepcopy(reader)
+    assert cloned.temperature == 12
+    assert not hasattr(cloned, "pressure")
+
+
+def test_dynamic_writer_ports(tmp_path: Path) -> None:
+    writer = FileWriter(name="writer", path=tmp_path / "data.csv", field_names=["temperature"])
+    assert writer.temperature is None
+    assert "temperature" not in vars(writer)
+    assert not hasattr(writer, "temprature")
+    writer.temperature = None
+    assert writer._field_inputs == {"temperature": None}
+    assert "temperature" in vars(writer)
+
+
 @pytest.mark.asyncio
 @pytest.mark.parametrize(
     "initial_values", [{"a": [-1], "b": [-2]}, {"a": [-2]}, {"a": [-2, -1]}, {}]