nodelet loader hides load error

[xqms]

As of commit 4670f32, load errors (such as undefined references) can be hidden under certain circumstances.

If the loader is constructed using the

Loader::Loader(const boost::function<boost::shared_ptr<Nodelet> (const std::string& lookup_name)>& create_instance)

constructor, the refresh_classes_ call in https://github.com/ros/nodelet_core/blob/indigo-devel/nodelet/src/loader.cpp#L272 will fail, causing an exception and hiding the initial load error from the user.

This means that e.g. rqt plugin developers get an error message like

[ERROR][/rqt_gui_cpp_node_26375->Loader::load]: Failed to load nodelet [nodelet_name] of type [nodelet_type]: call to empty boost::function

which is not very helpful.

[jdschw]

Hi,

I'm getting the error described above when I attempt to run rqt_image_view. I am on Ubuntu 14.04, using the ROS prebuilt rqt packages, i.e. on this project I'm a user, not a developer. Has this error been seen by other users, and if so, do you know if there is workaround?

[xqms]

There is no generic workaround. The bug in the nodelet_core package is that it displays this error message instead of the specific error that occurred, which misleads everyone involved.

To investigate your problem, you could build nodelet_core with my fix from #24, re-run the image viewer and report a bug on rqt_image_view with the specific error.

[xqms]

@esteve as this is affecting more people, would you consider merging my fix in #24? Nodelet development/debugging is really tedious without it.

[jdschw]

Thanks for the response. I was able to identify my problem through other means, and it was unrelated to this codebase, but the "true" error was indeed shadowed by the above error.

[esteve]

@xqms thanks for your patch and sorry for the slow response. Is there a way I could reproduce the issue? I'd like to add a regression test.

[xqms]

I've added a unit test to the PR. If you want to see it fail, check out 79dbd5b.

[esteve]

@xqms Thank you so much! Just merged it.

[DorianScholz]

This bug still persists on Hydro. Would it be possible to backport the PR #24 for Hydro?