Contributor Notes

Hi! Thanks for contributing. This page contains all the details about getting your dev environment setup.


This is documentation for contributors developing nunavut. If you are a user of this software you can ignore everything here.



I highly recommend using a virtual environment when doing python development. It’ll save you hours of lost productivity the first time it keeps you from pulling in an unexpected dependency from your global python environment. You can install virtualenv from brew on osx or apt-get on linux. I’d recommend the following environment for vscode:

git submodule update --init --recursive
virtualenv -p python3.7 .pyenv
source .pyenv/bin/activate
pip install -r requirements.txt
pip -e install .

Visual Studio Code

If you use vscode for python development you’ll need to tweak the following settings to get all the linters and previewers to work.

First off, use a virtualenv, installing the project’s requirements.txt and an editable version of the package itself.

This will enable running pytest from vscode. Now you can launch vscode for this repository:

code .

For the python interpreter select the local .venv and set flake8 and mypy as your linters (we don’t use pylint for this project). The rest of your python environment should now be functional.


The Python plugin for vscode comes with a full-featured Python debugger. To setup a debug session for nnvg open the launch.json for your workspace and add a configuration like the following to the configurations array:

    "name": "Python: nnvg",
    "type": "python",
    "request": "launch",
    "program": "${workspaceFolder}/src/nnvg",
    "cwd": "${workspaceFolder}",
    "console": "integratedTerminal",
    "args": ["--templates", "test/gentest_dsdl/templates",
                "--output-extension", ".h",


Note that each argument part must be a separate entry in the args array. Using a single space separated string does not work as you might expect since this results in a single string that contains spaces being passed as an argument.

The output for this example will appear under the default output directory for nnvg ${workspaceFolder}/nunavut_out

You can setup a debug session for unit tests using a similar launch configuration that invokes the pytest module. For example:

    "name": "Python: pyunit",
    "type": "python",
    "request": "launch",
    "module": "pytest",
    "cwd": "${workspaceFolder}/test",
    "console": "integratedTerminal",
    "args": ["--basetemp=${workspaceFolder}/build",
             "-p", "no:cacheprovider",
             "-k", "gentest_any"]

…where -k is a pattern to filter for a specific test or set of tests (Omit all args to debug all tests). The --basetemp and -p no:cacheprovider arguments prevent local testing from conflicting with tox test runs.


Here are some excerpts from my .vscode/settings.json to help you get your linting, unit-tests, and documentation previews all up and running.

I always work in a virtual environment. This selects the python version from that environment.

"python.pythonPath": ".pyenv/bin/python3.7",

We use flake8 and mypy as part of the build. Enabling them in your IDE will give you real-time feedback which makes your tox builds less interesting.

"python.linting.pylintEnabled": false,
"python.linting.mypyEnabled": true,
"python.linting.flake8Enabled": true,
"python.linting.enabled": true,

I’ve found the auto-discovery and pytest integration in vscode is very finicky. First, make sure you’ve done a pip install -e . for this repo (as described in the virtualenv section above). After that be sure you use these exact settings and it should work

"python.testing.cwd": "${workspaceFolder}",
"python.testing.unittestEnabled": false,
"python.testing.nosetestsEnabled": false,
"python.testing.pyTestEnabled": true,
"python.testing.pyTestArgs": ["--rootdir=${workspaceFolder}",

You’ll need to tweak two settings to get restructured text preview to work.

"restructuredtext.sphinxBuildPath": "sphinx-build",
"restructuredtext.confPath": "${workspaceFolder}/src"

If you installed everything in requirements.txt then the python extension for vscode will lint your .rst as you type and will support a fairly accurate reStructuredText preview.

Hopefully that helps. Let us know if these settings stop working.

Running The Tests

To run the full suite of tox tests locally you’ll need docker. Once you have docker installed and running do:

git submodule update --init --recursive
docker pull uavcan/toxic:py35-py38
docker run --rm -it -v /path/to/nunavut:/repo uavcan/toxic:py35-py38

import file mismatch

If you get an error like the following:

_____ ERROR collecting test/gentest_dsdl/ _______________________________________
import file mismatch:
imported module 'test_dsdl' has this __file__ attribute:
which is not the same as the test file we want to collect:
HINT: remove __pycache__ / .pyc files and/or use a unique basename for your test file modules

Then you are probably a wonderful developer that is running the unit-tests locally. Pytest’s cache is interfering with your docker test run. To work around this simply delete the pycache files. For example:

#! /usr/bin/env bash
cleandirs="src test"

for cleandir in $cleandirs
    find $cleandir -name __pycache__ | xargs rm -rf
    find $cleandir -name \.coverage\* | xargs rm -f

Note that we also delete the .coverage intermediates since they may contain different paths between the container and the host build.

Building The Docs

We rely on read the docs to build our documentation from github but we also verify this build as part of our tox build. This means you can view a local copy after completing a full, successful test run (See Running The Tests) or do docker run --rm -t -v /path/to/nunavut:/repo uavcan/toxic:py35-py38 /bin/sh -c "tox -e docs" to build the docs target. You can open the index.html under .tox/docs/tmp/index.html or run a local webserver:

python -m http.server --directory .tox/docs/tmp &
open http://localhost:8000/index.html

Of course, you can just use Visual Studio Code to build and preview the docs using > reStructuredText: Open Preview.

Coverage and Linting Reports

We publish the results of our coverage data to Codacy and the tox build will fail for any mypy or flake8 errors but you can view additional reports locally under the .tox dir.


We generate a local html coverage report. You can open the index.html under .tox/report/tmp or run a local webserver:

python -m http.server --directory .tox/report/tmp &
open http://localhost:8000/index.html


At the end of the mypy run we generate the following summaries:

  • .tox/mypy/tmp/mypy-report-lib/index.txt
  • .tox/mypy/tmp/mypy-report-script/index.txt