add hint if rclpy fails to be imported #116

mikaelarguedas · 2017-09-12T21:51:53Z

closes #115
connects to #115

Thew content of the referenced wiki page can be updated at a later date

Without this change

Failed to load entry point 'pub': DLL load failed: The specified module could not be found.
Traceback (most recent call last):
  File "C:\dev\ros2\lib\demo_nodes_py\talker-script.py", line 11, in <module>
    load_entry_point('demo-nodes-py==0.0.0', 'console_scripts', 'talker')()
  File "C:\Python36\lib\site-packages\pkg_resources\__init__.py", line 570, in load_entry_point
    return get_distribution(dist).load_entry_point(group, name)
  File "C:\Python36\lib\site-packages\pkg_resources\__init__.py", line 2687, in load_entry_point
    return ep.load()
  File "C:\Python36\lib\site-packages\pkg_resources\__init__.py", line 2341, in load
    return self.resolve()
  File "C:\Python36\lib\site-packages\pkg_resources\__init__.py", line 2347, in resolve
    module = __import__(self.module_name, fromlist=['__name__'], level=0)
  File "C:\dev\ros2\Lib\site-packages\demo_nodes_py\topics\talker.py", line 17, in <module>
    import rclpy
  File "C:\dev\ros2\Lib\site-packages\rclpy\__init__.py", line 17, in <module>
    from rclpy.executors import SingleThreadedExecutor as _SingleThreadedExecutor
  File "C:\dev\ros2\Lib\site-packages\rclpy\executors.py", line 21, in <module>
    from rclpy.impl.implementation_singleton import rclpy_implementation as _rclpy
  File "C:\dev\ros2\Lib\site-packages\rclpy\impl\implementation_singleton.py", line 32, in <module>
    rclpy_implementation = importlib.import_module('._rclpy', package='rclpy')
  File "C:\Python36\lib\importlib\__init__.py", line 126, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
ImportError: DLL load failed: The specified module could not be found.

With this change

Failed to load entry point 'pub': DLL load failed: The specified module could not be found.
The module '._rclpy' failed to be imported while being present on the system. Please refer to 'https://github.com/ros2/ros2/wiki/Rclpy-Import-error-hint' for possible solutions

Traceback (most recent call last):
  File "C:\dev\ros2\lib\demo_nodes_py\talker-script.py", line 11, in <module>
    load_entry_point('demo-nodes-py==0.0.0', 'console_scripts', 'talker')()
  File "C:\Python36\lib\site-packages\pkg_resources\__init__.py", line 570, in load_entry_point
    return get_distribution(dist).load_entry_point(group, name)
  File "C:\Python36\lib\site-packages\pkg_resources\__init__.py", line 2687, in load_entry_point
    return ep.load()
  File "C:\Python36\lib\site-packages\pkg_resources\__init__.py", line 2341, in load
    return self.resolve()
  File "C:\Python36\lib\site-packages\pkg_resources\__init__.py", line 2347, in resolve
    module = __import__(self.module_name, fromlist=['__name__'], level=0)
  File "C:\dev\ros2\Lib\site-packages\demo_nodes_py\topics\talker.py", line 17, in <module>
    import rclpy
  File "C:\dev\ros2\Lib\site-packages\rclpy\__init__.py", line 17, in <module>
    from rclpy.executors import SingleThreadedExecutor as _SingleThreadedExecutor
  File "C:\dev\ros2\Lib\site-packages\rclpy\executors.py", line 21, in <module>
    from rclpy.impl.implementation_singleton import rclpy_implementation as _rclpy
  File "C:\dev\ros2\Lib\site-packages\rclpy\impl\implementation_singleton.py", line 35, in <module>
    rclpy_implementation = importlib.import_module(module_name, package='rclpy')
  File "C:\Python36\lib\importlib\__init__.py", line 126, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
ImportError: DLL load failed: The specified module could not be found.

Alternatively we could not reraise the exception and exit. That will give a cleaner error message but has the downside of restricting user ability to catch it and fallback. So I settled on the current behavior
Without reraising

Failed to load entry point 'pub': DLL load failed: The specified module could not be found.
The module '._rclpy' failed to be imported while being present on the system. Please refer to 'https://github.com/ros2/ros2/wiki/Rclpy-Import-error-hint' for possible solutions

sloretz · 2017-09-12T21:59:46Z

rclpy/rclpy/impl/implementation_singleton.py

+    import os
+    if os.path.isfile(e.path):
+        import sys
+        print(


Use warnings module instead of printing? I think it would allow an advanced user to suppress the output, though I can't think of a use case for that.

dirk-thomas · 2017-09-12T22:01:32Z

rclpy/rclpy/impl/implementation_singleton.py

+try:
+    rclpy_implementation = importlib.import_module(module_name, package='rclpy')
+except ImportError as e:
+    import os


This import should at module level. No need to do it in this local scope. Same for sys below.

dirk-thomas · 2017-09-12T22:03:10Z

rclpy/rclpy/impl/implementation_singleton.py

+        print(
+            "The module '%s' failed to be imported while being present on the system."
+            " Please refer to '%s' for possible solutions\n" %
+            (module_name, 'https://github.com/ros2/ros2/wiki/Rclpy-Import-error-hint'),


I would rather print e.path here since module_name is already part of the exception string. The message could start with "The C extension '%s' failed ..." then.

mikaelarguedas · 2017-09-12T22:15:23Z

new message:

Failed to load entry point 'pub': The C extension 'C:\dev\ros2\Lib\site-packages\rclpy\_rclpy.pyd' failed to be imported while being present on the system. Please refer to 'https://github.com/ros2/ros2/wiki/Rclpy-Import-error-hint' for possible solutions

Traceback (most recent call last):
  File "C:\dev\ros2\Lib\site-packages\rclpy\impl\implementation_singleton.py", line 33, in <module>
    rclpy_implementation = importlib.import_module('._rclpy', package='rclpy')
  File "C:\Python36\lib\importlib\__init__.py", line 126, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
  File "<frozen importlib._bootstrap>", line 978, in _gcd_import
  File "<frozen importlib._bootstrap>", line 961, in _find_and_load
  File "<frozen importlib._bootstrap>", line 950, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 648, in _load_unlocked
  File "<frozen importlib._bootstrap>", line 560, in module_from_spec
  File "<frozen importlib._bootstrap_external>", line 922, in create_module
  File "<frozen importlib._bootstrap>", line 205, in _call_with_frames_removed
ImportError: DLL load failed: The specified module could not be found.

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "C:\dev\ros2\lib\demo_nodes_py\talker-script.py", line 11, in <module>
    load_entry_point('demo-nodes-py==0.0.0', 'console_scripts', 'talker')()
  File "C:\Python36\lib\site-packages\pkg_resources\__init__.py", line 570, in load_entry_point
    return get_distribution(dist).load_entry_point(group, name)
  File "C:\Python36\lib\site-packages\pkg_resources\__init__.py", line 2687, in load_entry_point
    return ep.load()
  File "C:\Python36\lib\site-packages\pkg_resources\__init__.py", line 2341, in load
    return self.resolve()
  File "C:\Python36\lib\site-packages\pkg_resources\__init__.py", line 2347, in resolve
    module = __import__(self.module_name, fromlist=['__name__'], level=0)
  File "C:\dev\ros2\Lib\site-packages\demo_nodes_py\topics\talker.py", line 17, in <module>
    import rclpy
  File "C:\dev\ros2\Lib\site-packages\rclpy\__init__.py", line 17, in <module>
    from rclpy.executors import SingleThreadedExecutor as _SingleThreadedExecutor
  File "C:\dev\ros2\Lib\site-packages\rclpy\executors.py", line 21, in <module>
    from rclpy.impl.implementation_singleton import rclpy_implementation as _rclpy
  File "C:\dev\ros2\Lib\site-packages\rclpy\impl\implementation_singleton.py", line 39, in <module>
    (e.path, 'https://github.com/ros2/ros2/wiki/Rclpy-Import-error-hint'))
ImportWarning: The C extension 'C:\dev\ros2\Lib\site-packages\rclpy\_rclpy.pyd' failed to be imported while being present on the system. Please refer to 'https://github.com/ros2/ros2/wiki/Rclpy-Import-error-hint' for possible solutions

dirk-thomas · 2017-09-12T22:16:54Z

rclpy/rclpy/impl/implementation_singleton.py

+    rclpy_implementation = importlib.import_module('._rclpy', package='rclpy')
+except ImportError as e:
+    if os.path.isfile(e.path):
+        raise ImportWarning(


I don't think this should be an ImportWarning. I thought @sloretz was referring to call warnings.warn(...).

Yeah I figured I just liked the idea of the message being the last thing the user see rather than having to scroll up the stack trace to see our message burried in the middle.
But I agree it's less semantically correct

You could also extend the msg of the raised exception e to add additional information if you prefer a single message.

This reverts commit e32ece2.

dirk-thomas · 2017-09-12T22:28:07Z

rclpy/rclpy/impl/implementation_singleton.py

+    if os.path.isfile(e.path):
+        warnings.warn(
+            "The C extension '%s' failed to be imported while being present on the system."
+            " Please refer to '%s' for possible solutions\n" %


Is the trailing \n necessary?

It was not necessary but made the custom message not visible at all originally that's why I added it. Not that it's part of the exception message it's not necessary anymore

dirk-thomas · 2017-09-12T22:33:49Z

rclpy/rclpy/impl/implementation_singleton.py

+    if os.path.isfile(e.path):
+        e.msg += \
+            "\nThe C extension '%s' failed to be imported while being present on the system." \
+            " Please refer to '%s' for possible solutions\n" % \


Why should this have a trailing newline?

dirk-thomas

LGTM. Can you post the resulting stacktrace?

mikaelarguedas · 2017-09-12T22:41:31Z

Resulting stack trace:

Failed to load entry point 'pub': DLL load failed: The specified module could not be found.
The C extension 'C:\dev\ros2\Lib\site-packages\rclpy\_rclpy.pyd' failed to be imported while being present on the system. Please refer to 'https://github.com/ros2/ros2/wiki/Rclpy-Import-error-hint' for possible solutions

Traceback (most recent call last):
  File "C:\dev\ros2\lib\demo_nodes_py\talker-script.py", line 11, in <module>
    load_entry_point('demo-nodes-py==0.0.0', 'console_scripts', 'talker')()
  File "C:\Python36\lib\site-packages\pkg_resources\__init__.py", line 570, in load_entry_point
    return get_distribution(dist).load_entry_point(group, name)
  File "C:\Python36\lib\site-packages\pkg_resources\__init__.py", line 2687, in load_entry_point
    return ep.load()
  File "C:\Python36\lib\site-packages\pkg_resources\__init__.py", line 2341, in load
    return self.resolve()
  File "C:\Python36\lib\site-packages\pkg_resources\__init__.py", line 2347, in resolve
    module = __import__(self.module_name, fromlist=['__name__'], level=0)
  File "C:\dev\ros2\Lib\site-packages\demo_nodes_py\topics\talker.py", line 17, in <module>
    import rclpy
  File "C:\dev\ros2\Lib\site-packages\rclpy\__init__.py", line 17, in <module>
    from rclpy.executors import SingleThreadedExecutor as _SingleThreadedExecutor
  File "C:\dev\ros2\Lib\site-packages\rclpy\executors.py", line 21, in <module>
    from rclpy.impl.implementation_singleton import rclpy_implementation as _rclpy
  File "C:\dev\ros2\Lib\site-packages\rclpy\impl\implementation_singleton.py", line 33, in <module>
    rclpy_implementation = importlib.import_module('._rclpy', package='rclpy')
  File "C:\Python36\lib\importlib\__init__.py", line 126, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
ImportError: DLL load failed: The specified module could not be found.
The C extension 'C:\dev\ros2\Lib\site-packages\rclpy\_rclpy.pyd' failed to be imported while being present on the system. Please refer to 'https://github.com/ros2/ros2/wiki/Rclpy-Import-error-hint' for possible solutions

add hint if rclpy fails to be imported

8513b4f

mikaelarguedas added in progress Actively being worked on (Kanban column) in review Waiting for review (Kanban column) and removed in progress Actively being worked on (Kanban column) labels Sep 12, 2017

sloretz reviewed Sep 12, 2017

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dirk-thomas reviewed Sep 12, 2017

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mikaelarguedas added 2 commits September 12, 2017 15:08

use e.path and import at module level

acbee45

raise import warning

e32ece2

dirk-thomas reviewed Sep 12, 2017

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mikaelarguedas added 2 commits September 12, 2017 15:18

Revert "raise import warning"

ebb3dcc

This reverts commit e32ece2.

use warn

f5e64b9

dirk-thomas reviewed Sep 12, 2017

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mikaelarguedas added 2 commits September 12, 2017 15:30

extend error message

332295a

remove trailin newline now that this is the exception message

def81f5

dirk-thomas reviewed Sep 12, 2017

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dirk-thomas approved these changes Sep 12, 2017

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sloretz approved these changes Sep 12, 2017

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mikaelarguedas merged commit 829a4ff into master Sep 12, 2017

mikaelarguedas deleted the add_hint_for_fail_import branch September 12, 2017 22:46

mikaelarguedas removed the in review Waiting for review (Kanban column) label Sep 12, 2017

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add hint if rclpy fails to be imported #116

add hint if rclpy fails to be imported #116

mikaelarguedas commented Sep 12, 2017 •

edited

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sloretz Sep 12, 2017

dirk-thomas Sep 12, 2017

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edited

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mikaelarguedas commented Sep 12, 2017

add hint if rclpy fails to be imported #116

add hint if rclpy fails to be imported #116

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mikaelarguedas commented Sep 12, 2017

mikaelarguedas commented Sep 12, 2017 •

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