initial a2a-pack

a2a_pack/cli/loader.py

@@ -0,0 +1,34 @@
+"""Load an :class:`A2AAgent` subclass from a string entrypoint."""
+from __future__ import annotations
+
+import importlib
+import sys
+from pathlib import Path
+
+from ..agent import A2AAgent
+
+
+def load_agent_class(entrypoint: str, *, project_dir: Path | None = None) -> type[A2AAgent]:
+    """Resolve ``module:ClassName`` to an :class:`A2AAgent` subclass.
+
+    If ``project_dir`` is given, it is prepended to ``sys.path`` so a local
+    ``agent.py`` can be imported without packaging.
+    """
+    if ":" not in entrypoint:
+        raise ValueError(
+            f"entrypoint must be 'module:ClassName' (got {entrypoint!r})"
+        )
+    module_name, class_name = entrypoint.split(":", 1)
+
+    if project_dir is not None:
+        path = str(project_dir.resolve())
+        if path not in sys.path:
+            sys.path.insert(0, path)
+
+    module = importlib.import_module(module_name)
+    obj = getattr(module, class_name, None)
+    if obj is None:
+        raise AttributeError(f"{module_name} has no attribute {class_name!r}")
+    if not isinstance(obj, type) or not issubclass(obj, A2AAgent):
+        raise TypeError(f"{entrypoint} is not an A2AAgent subclass")
+    return obj