Roman's Notes: How to debug neovim python remote plugin

Friday, March 11, 2016

How to debug neovim python remote plugin

I really really really want to have debugger integration with my Vim setup and while the plugins for old Vim were a little wacky, the new architecture of NeoVim seems promising, so I decided to give lldb.nvim a go.

It didn't work. This is a (~~epic~~ boring) story of how I debugged and fixed the issues.

Step 1: update

Update your neovim to the latest release to avoid fighting issues that have already been solved. At the time of writing, I used:

nvim 0.1.2 from Homebrew
OS X 10.10.5
XCode 7.0
lldb-340.4.70

Step 2: Diagnose

PyThreadState_get error

If you're on OS X, chances are you have more than one Python version installed and that's where the trouble comes from. If you get this error message

>>> import lldb
Fatal Python error: PyThreadState_Get: no current thread

it's most likely because you're trying to import a module that has been linked with a different version of Python. The lldb module comes with the XCode developer tools and was linked with the default system version of Python which lives in (remember this)

/System/Library/Frameworks/Python.framework/Versions/2.7/bin/python

so this is the python version you should use to run the lldb.nvim remote plugin. On my system, BTW, lldb module lives in

/Applications/Xcode.app/Contents/SharedFrameworks/LLDB.framework/Resources/Python

Step 3: Install neovim Python module

The neovim module has probably already been installed with neovim but perhaps not in the correct Python version. You can try to import neovim in the system Python. If it fails, you'll need to install it using easy_install or pip:

sudo /System/Library/Frameworks/Python.framework/Versions/2.7/bin/python -m easy_install neovim

This will install the neovim package into the system Python distribution (needs sudo) using the easy_install tool.

Step 4: Configure neovim to use the system Python

In your neovim config file, add this line:

let g:python_host_prog = '/System/Library/Frameworks/Python.framework/Versions/2.7/bin/python'

This ensures that neovim will start the system Python (which has access to lldb and neovim modules) to host the plugin. After this, you should be all set!

Step 5: Using $PYTHONPATH?

If you do use $PYTHONPATH with your non-system Python, you'll have trouble as well. Before launching the system Python from nvim, you'll need to clean this variable otherwise the packages will interfere with the system Python's packages.

I do that using a small wrapper script ~/syspython2 which gets invoked from nvim as the g:python_host_prog

#!/bin/sh
# running the OS X system python. Required to import the lldb module.
export PYTHONPATH="/Applications/Xcode.app/Contents/SharedFrameworks/LLDB.framework/Resources/Python"

# enable these for debugging
#echo "--" >> ~/syspython2.log
#echo "$@" >> ~/syspython2.log
/System/Library/Frameworks/Python.framework/Versions/2.7/bin/python "$@"

Step 6: Diagnose

Still having trouble?

Don't forget to run :UpdateRemotePlugins
Enable logging in the ~/syspython2 script
Check using pstree | less if neovim is launching the correct Python binary
Double-check you can import neovim and lldb modules from the system Python
Make sure lldb.neovim is installed correctly - the file lldb.nvim/rplugin/python/lldb_nvim.py must exist
NeoVim also tries to load Python 3 plugins, you may need to do the same for Python 3
Try to debug /usr/local/Cellar/neovim/0.1.2/share/nvim/runtime/autoload/remote/host.vim using debugging vim methods
More info about lldb Python module here on StackOverflow

7 comments:

The YokerAugust 24, 2016 at 6:56 AM
Thanks a million trillion times! I was getting suicidal,
Here's one hundred smilies:
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Ales TsurkoNovember 17, 2016 at 4:52 AM
lldb works smooth with the default macOS python (/usr/bin/python). Which is also used in LLDB Python Reference: http://lldb.llvm.org/python-reference.html
But there is a need to install all the dependencies and even pip itself for this version. My workaround was:
1) installing pip with /usr/bin/python using get-pip.py (no luck with easy_install):
download https://bootstrap.pypa.io/get-pip.py
run the downloaded: sudo /usr/bin/python get-pip.py
2) installing the 'six' module (sudo /usr/bin/python -m pip install six)
3) installing neovim, but 'pip install' for each dependency:
sudo /usr/bin/python -m pip install greenlet
sudo /usr/bin/python -m pip install msgpack-python
sudo /usr/bin/python -m pip install futures
sudo /usr/bin/python -m pip install trollius
sudo /usr/bin/python -m pip install neovim
4) adding 'export PYTHONPATH=/Developer/Library/PrivateFrameworks/LLDB.framework/Resources/Python' to my ~/.bash_profile
5) setting nvim's python to /usr/bin/python
let g:python_host_prog = '/usr/bin/python'
But this is clean Python on my system, all the modules that I previously installed is in /System/Library/Frameworks/Python.framework/... so it's not so great.
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Hamid RohaniDecember 6, 2016 at 4:31 AM
Thanks for your great tutorial. I had problem with addressing python host like this:
let g:python_host_prog = '~/syspython2'
This should be:
let g:python_host_prog = '/Users/username/syspython2'
With this configuration it works :)
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CrebsMay 4, 2017 at 9:57 AM
Thank you. Excited to use lldb in neovim now!
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marksonSeptember 16, 2019 at 12:55 AM
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