Handle creating exposed actions as needed regardless of import order (#4)

* Handle creating exposed actions as needed regardless of import order

Author: emersonknapp

CMakeLists.txt

@@ -12,7 +12,7 @@ if(BUILD_TESTING)
   ament_lint_auto_find_test_dependencies()
 
   find_package(ament_cmake_pytest REQUIRED)
-  ament_add_pytest_test(test_all test)
+  ament_add_pytest_test(test_pytests test)
 endif()
 
 ament_package()

launch_py/actions.py

@@ -14,37 +14,53 @@
 
 from typing import Any, Callable
 
-from launch.frontend.expose import action_parse_methods
-
 from .entity import Entity, is_reserved_identifier
 
 __all__ = []
 
 
-def make_action_factory(action_name: str, **kwargs) -> Callable[..., Entity]:
+def make_action_factory(action_name: str, **kwargs) -> Callable[..., Any]:
     # Create a factory function for each action entity
+    if is_reserved_identifier(action_name):
+        action_name += '_'
+
     def fn(**kwargs):
-        return Entity(action_name, kwargs)  # noqa: F821
+        return Entity(action_name, kwargs)
 
-    # fn = FunctionType(impl_template.__code__, globals(), name=action_name)
     fn.__doc__ = f'launch_py action: {action_name} (dynamically generated)'
     fn.__name__ = action_name
     fn.__qualname__ = action_name
     fn.__module__ = __name__
+    globals()[action_name] = fn
+    __all__.append(action_name)
     return fn
 
 
-for action_name in action_parse_methods.keys():
-    if is_reserved_identifier(action_name):
-        action_name += '_'
-    fn = make_action_factory(action_name)
-    globals()[action_name] = fn
-    __all__.append(action_name)
+def preseed_all_actions() -> None:
+    """Pre-seed all actions in the module."""
+    from launch.frontend.expose import action_parse_methods
+
+    for action_name in action_parse_methods.keys():
+        make_action_factory(action_name)
 
 
 def __getattr__(name: str) -> Any:
-    # This is a workaround for mypy complaint about dynamically created attrs
+    from launch.frontend.expose import action_parse_methods
     import importlib
+
+    # If it's already been created, return
     if name in __all__:
         return importlib.import_module(f'.{name}', __name__)
-    raise AttributeError(f'module {__name__} has no attribute {name}')
+
+    # If not, perhaps it was exposed later or not accessed yet
+    base_name = name[:-1] if name.endswith('_') else name
+    if base_name in action_parse_methods:
+        return make_action_factory(name)
+    else:
+        msg = f'module {__name__} has no attribute "{name}"'
+        if base_name != name:
+            msg += ' (or "{base_name}")'
+        raise AttributeError(msg)
+
+
+preseed_all_actions()

test/test_action_list_preseed.py

@@ -0,0 +1,23 @@
+# Copyright 2025 Polymath Robotics, Inc.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import launch_py
+
+
+def test_action_list_preseed():
+    # We can construct entities on the fly, but we want to make sure the list is
+    # already filled where possible without explicit access
+    # picking a representative subset of actions (that are present in Humble+)
+    for x in ['arg', 'timer', 'executable', 'let', 'group', 'include', 'set_env']:
+        assert x in launch_py.actions.__all__

test/test_dynamic_attrs.py

@@ -14,26 +14,28 @@
 
 from launch.action import Action
 from launch.frontend import expose_action
+from launch_py import actions
 import pytest
 
 
 @expose_action('while')
 class BuiltinNameTest(Action):
     """Test action that exposes a Python builtin name."""
 
-    def __init__(self, **kwargs):
-        super().__init__(**kwargs)
-
     @classmethod
     def parse(cls, entity, parser):
         _, kwargs = super().parse(entity, parser)
         return cls, kwargs
 
-    def execute(self, context):
-        del context
 
+@expose_action('foo')
+class DynamicCreationTest(Action):
+    """Test action that exposes an action after first import."""
 
-from launch_py import actions  # noqa: I100, E402
+    @classmethod
+    def parse(cls, entity, parser):
+        _, kwargs = super().parse(entity, parser)
+        return cls, kwargs
 
 
 def test_dynamic_attrs():
@@ -42,8 +44,6 @@ def test_dynamic_attrs():
     str_repr = str(actions.let)
     assert str_repr.startswith('<function let')
 
-    assert actions.while_.__name__ == 'while_'
-
     with pytest.raises(AttributeError):
         getattr(actions, 'non_existent_action')
 
@@ -57,3 +57,18 @@ def test_dynamic_attrs():
 
     with pytest.raises(AttributeError):
         test_arg.get_attr('non_existent_attr')
+
+
+def test_dynamic_create():
+    assert actions.foo is not None
+
+    assert actions.foo.__name__ == 'foo'
+    assert actions.foo().type_name == 'foo'
+
+    with pytest.raises(AttributeError):
+        actions.node
+
+
+def test_bultin_suffix():
+    assert actions.while_.__name__ == 'while_'
+    assert actions.while_().type_name == 'while_'