Avoid the limitation of not being able to import rclpy C extensions at module level [alternative]

rclpy/CMakeLists.txt

@@ -29,15 +29,15 @@ if(WIN32 AND CMAKE_BUILD_TYPE STREQUAL "Debug")
 endif()
 
 # enables using the Python extensions from the build space for testing
-file(WRITE "${CMAKE_CURRENT_BINARY_DIR}/test_rclpy/__init__.py" "")
+file(WRITE "${CMAKE_CURRENT_BINARY_DIR}/${PROJECT_NAME}_impl/__init__.py" "")
 
 ament_python_install_package(${PROJECT_NAME})
 
 function(set_properties _targetname _build_type)
   set_target_properties(${_targetname} PROPERTIES
     PREFIX ""
-    LIBRARY_OUTPUT_DIRECTORY${_build_type} "${CMAKE_CURRENT_BINARY_DIR}/test_${PROJECT_NAME}"
-    RUNTIME_OUTPUT_DIRECTORY${_build_type} "${CMAKE_CURRENT_BINARY_DIR}/test_${PROJECT_NAME}"
+    LIBRARY_OUTPUT_DIRECTORY${_build_type} "${CMAKE_CURRENT_BINARY_DIR}/${PROJECT_NAME}_impl"
+    RUNTIME_OUTPUT_DIRECTORY${_build_type} "${CMAKE_CURRENT_BINARY_DIR}/${PROJECT_NAME}_impl"
     OUTPUT_NAME "_${_targetname}${PythonExtra_EXTENSION_SUFFIX}"
     SUFFIX "${PythonExtra_EXTENSION_EXTENSION}")
 endfunction()
@@ -67,7 +67,7 @@ function(configure_python_c_extension_library _library_name)
   )
 
   install(TARGETS ${_library_name}
-    DESTINATION "${PYTHON_INSTALL_DIR}/${PROJECT_NAME}"
+    DESTINATION "${PYTHON_INSTALL_DIR}/${PROJECT_NAME}_impl"
   )
 endfunction()
 
@@ -97,6 +97,11 @@ install(TARGETS rclpy_common
   RUNTIME DESTINATION bin
 )
 
+install(FILES
+  "${CMAKE_CURRENT_BINARY_DIR}/${PROJECT_NAME}_impl/__init__.py"
+  DESTINATION "${PYTHON_INSTALL_DIR}/${PROJECT_NAME}_impl"
+)
+
 add_library(
   rclpy
   SHARED src/rclpy/_rclpy.c

rclpy/rclpy/__init__.py

@@ -45,6 +45,7 @@
 from typing import TYPE_CHECKING
 
 from rclpy.context import Context
+from rclpy.impl.implementation_singleton import rclpy_implementation
 from rclpy.parameter import Parameter
 from rclpy.task import Future
 from rclpy.utilities import get_default_context
@@ -68,8 +69,6 @@ def init(*, args: List[str] = None, context: Context = None) -> None:
         (see :func:`.get_default_context`).
     """
     context = get_default_context() if context is None else context
-    # imported locally to avoid loading extensions on module import
-    from rclpy.impl.implementation_singleton import rclpy_implementation
     return rclpy_implementation.rclpy_init(args if args is not None else sys.argv, context.handle)
 
 

rclpy/rclpy/context.py

@@ -15,6 +15,8 @@
 import threading
 from typing import Callable
 
+from rclpy.impl.implementation_singleton import rclpy_implementation
+
 
 class Context:
     """
@@ -26,7 +28,6 @@ class Context:
     """
 
     def __init__(self):
-        from rclpy.impl.implementation_singleton import rclpy_implementation
         self._handle = rclpy_implementation.rclpy_create_context()
         self._lock = threading.Lock()
         self._callbacks = []
@@ -38,8 +39,6 @@ def handle(self):
 
     def ok(self):
         """Check if context hasn't been shut down."""
-        # imported locally to avoid loading extensions on module import
-        from rclpy.impl.implementation_singleton import rclpy_implementation
         with self._lock:
             return rclpy_implementation.rclpy_ok(self._handle)
 
@@ -51,16 +50,12 @@ def _call_on_shutdown_callbacks(self):
 
     def shutdown(self):
         """Shutdown this context."""
-        # imported locally to avoid loading extensions on module import
-        from rclpy.impl.implementation_singleton import rclpy_implementation
         with self._lock:
             rclpy_implementation.rclpy_shutdown(self._handle)
         self._call_on_shutdown_callbacks()
 
     def try_shutdown(self):
         """Shutdown this context, if not already shutdown."""
-        # imported locally to avoid loading extensions on module import
-        from rclpy.impl.implementation_singleton import rclpy_implementation
         with self._lock:
             if rclpy_implementation.rclpy_ok(self._handle):
                 rclpy_implementation.rclpy_shutdown(self._handle)

rclpy/rclpy/impl/__init__.py

@@ -18,7 +18,7 @@
 
 def _import(name):
     try:
-        return importlib.import_module(name, package='rclpy')
+        return importlib.import_module(name, package='rclpy_impl')
     except ImportError as e:
         if e.path is not None and os.path.isfile(e.path):
             e.msg += \

rclpy/rclpy/utilities.py

@@ -17,6 +17,7 @@
 
 from rclpy.constants import S_TO_NS
 from rclpy.context import Context
+from rclpy.impl.implementation_singleton import rclpy_implementation
 
 g_default_context = None
 g_context_lock = threading.Lock()
@@ -37,8 +38,6 @@ def get_default_context(*, shutting_down=False):
 
 
 def remove_ros_args(args=None):
-    # imported locally to avoid loading extensions on module import
-    from rclpy.impl.implementation_singleton import rclpy_implementation
     return rclpy_implementation.rclpy_remove_ros_args(
         args if args is not None else sys.argv)
 
@@ -63,8 +62,6 @@ def try_shutdown(*, context=None):
 
 
 def get_rmw_implementation_identifier():
-    # imported locally to avoid loading extensions on module import
-    from rclpy.impl.implementation_singleton import rclpy_implementation
     return rclpy_implementation.rclpy_get_rmw_implementation_identifier()
 
 

rclpy/test/__init__.py

@@ -1,29 +0,0 @@
-# Copyright 2016-2017 Open Source Robotics Foundation, 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 importlib
-import sys
-
-assert 'rclpy' not in sys.modules, 'rclpy should not have been imported before running tests'
-
-# this will make the extensions load from the build folder
-import rclpy.impl  # noqa
-import test_rclpy  # noqa
-
-
-def _custom_import(name):
-    return importlib.import_module(name, package='test_rclpy')
-
-
-rclpy.impl._import = _custom_import