feat(execution): add executor registry (register/get only)

src/lfx/src/lfx/execution/registry.py

@@ -0,0 +1,27 @@
+"""Executor registry."""
+
+from __future__ import annotations
+
+from typing import TYPE_CHECKING
+
+if TYPE_CHECKING:
+    from lfx.execution.executor import Executor
+
+
+class ExecutorNotFoundError(LookupError):
+    pass
+
+
+class ExecutorRegistry:
+    def __init__(self) -> None:
+        self._by_kind: dict[str, Executor] = {}
+
+    def register(self, executor: Executor) -> None:
+        self._by_kind[executor.kind] = executor
+
+    def get(self, kind: str) -> Executor:
+        try:
+            return self._by_kind[kind]
+        except KeyError as exc:
+            msg = f"No executor registered for kind={kind!r}"
+            raise ExecutorNotFoundError(msg) from exc

src/lfx/tests/unit/execution/test_registry.py

@@ -0,0 +1,31 @@
+import pytest
+from lfx.execution.executor import Executor
+from lfx.execution.registry import ExecutorNotFoundError, ExecutorRegistry
+
+
+class _Stub(Executor):
+    kind = "stub"
+
+    async def execute(self, unit):  # noqa: ARG002
+        return
+        yield
+
+
+def test_register_and_get_by_kind():
+    registry = ExecutorRegistry()
+    registry.register(_Stub())
+    assert registry.get("stub").kind == "stub"
+
+
+def test_get_unknown_raises():
+    with pytest.raises(ExecutorNotFoundError, match="nope"):
+        ExecutorRegistry().get("nope")
+
+
+def test_register_replaces_same_kind():
+    registry = ExecutorRegistry()
+    a = _Stub()
+    b = _Stub()
+    registry.register(a)
+    registry.register(b)
+    assert registry.get("stub") is b