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

rclpy/CMakeLists.txt

@@ -28,16 +28,16 @@ if(WIN32 AND CMAKE_BUILD_TYPE STREQUAL "Debug")
   set(PYTHON_EXECUTABLE "${PYTHON_EXECUTABLE_DEBUG}")
 endif()
 
-# enables using the Python extensions from the build space for testing
-file(WRITE "${CMAKE_CURRENT_BINARY_DIR}/test_rclpy/__init__.py" "")
-
 ament_python_install_package(${PROJECT_NAME})
 
+# enables using the Python extensions from the build space for testing
+configure_file("resource/__init__.py.in" "${PROJECT_NAME}/__init__.py" @ONLY)
+
 function(set_properties _targetname _build_type)
   set_target_properties(${_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}/${PROJECT_NAME}"
+    RUNTIME_OUTPUT_DIRECTORY${_build_type} "${CMAKE_CURRENT_BINARY_DIR}/${PROJECT_NAME}"
     OUTPUT_NAME "_${_targetname}${PythonExtra_EXTENSION_SUFFIX}"
     SUFFIX "${PythonExtra_EXTENSION_EXTENSION}")
 endfunction()
@@ -218,7 +218,7 @@ if(BUILD_TESTING)
     ament_add_pytest_test(${_test_name} ${_test_path}
       PYTHON_EXECUTABLE "${PYTHON_EXECUTABLE}"
       APPEND_ENV AMENT_PREFIX_PATH=${ament_index_build_path}
-        PYTHONPATH=${CMAKE_CURRENT_BINARY_DIR}
+      ENV RCLPY_TEST_LIBRARY_DIR=${CMAKE_CURRENT_BINARY_DIR}
       TIMEOUT 60
       WERROR ON
     )

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/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/resource/__init__.py.in

@@ -0,0 +1,35 @@
+# -*- coding: utf-8 -*-
+# generated from rclpy/resource/__init__.py.in
+# keep symbol table as clean as possible by deleting all unnecessary symbols
+
+from os import path as os_path
+from pkgutil import extend_path
+from sys import path as sys_path
+
+source_path = '@CMAKE_CURRENT_SOURCE_DIR@'
+sys_path.insert(0, source_path)
+del sys_path
+
+__path__ = extend_path(__path__, __name__)
+del extend_path
+
+__execfiles = []
+src_init_file = os_path.join(source_path, __name__ + '.py')
+if os_path.isfile(src_init_file):
+    __execfiles.append(src_init_file)
+else:
+    src_init_file = os_path.join(source_path, __name__, '__init__.py')
+    if os_path.isfile(src_init_file):
+        __execfiles.append(src_init_file)
+del os_path
+del src_init_file
+del source_path
+
+for __execfile in __execfiles:
+    with open(__execfile, 'r') as __fh:
+        __code_object = compile(__fh.read(), __execfile, 'exec')
+        exec(__code_object)
+        del __code_object
+    del __fh
+    del __execfile
+del __execfiles

rclpy/test/__init__.py

@@ -12,18 +12,13 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-import importlib
+import os
 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
+# this will load rclpy from the build folder
+sys.path.insert(0, os.environ.get('RCLPY_TEST_LIBRARY_DIR'))
 
-
-def _custom_import(name):
-    return importlib.import_module(name, package='test_rclpy')
-
-
-rclpy.impl._import = _custom_import
+import rclpy  # noqa
+assert rclpy  # silence pyflakes