CONTRIBUTING.md

Contributing

Welcome to causalimpact contributor's guide.

This document focuses on getting any potential contributor familiarized with the development processes, but other kinds of contributions are also appreciated.

If you are new to using git or have never collaborated in a project previously, please have a look at contribution-guide.org. Other resources are also listed in the excellent guide created by FreeCodeCamp[^1].

Please notice, all users and contributors are expected to be open, considerate, reasonable, and respectful. When in doubt, Python Software Foundation's Code of Conduct is a good reference in terms of behavior guidelines.

Issue Reports

If you experience bugs or general issues with causalimpact, please have a look on the issue tracker. If you don't see anything useful there, please feel free to fire an issue report.

Please don't forget to include the closed issues in your search. Sometimes a solution was already reported, and the problem is considered solved.

New issue reports should include information about your programming environment (e.g., operating system, Python version) and steps to reproduce the problem. Please try also to simplify the reproduction steps to a very minimal example that still illustrates the problem you are facing. By removing other factors, you help us to identify the root cause of the issue.

Documentation Improvements

You can help improve causalimpact docs by making them more readable and coherent, or by adding missing information and correcting mistakes.

causalimpact documentation uses as its main documentation compiler. This means that the docs are kept in the same repository as the project code, and that any documentation update is done in the same way as a code contribution.

Documentation is written in the markdown language conforming to the CommonMark spec

Using the Github web editor

Please notice that the GitHub web interface provides a quick way of propose changes in causalimpact's files. While this mechanism can be tricky for normal code contributions, it works perfectly fine for contributing to the docs, and can be quite handy.

If you are interested in trying this method out, please navigate to the docs folder in the source repository, find which file you would like to propose changes and click in the little pencil icon at the top, to open GitHub's code editor. Once you finish editing the file, please write a message in the form at the bottom of the page describing which changes have you made and what are the motivations behind them and submit your proposal.

Using github.dev

github.dev also provides a convenient way to spin up a vscode editor in your browser for small changes.

Working locally

When working on documentation changes in your local machine, you can preview them using your IDE's markdown preview

Example: vscode guide

Code Contributions

Internals

The package exports the CausalImpact class which encapsulates the full range of functionality exposed to the user. This class is defined in src/causalimpact/analysis.py which is responsible for orchestrating the causalimpact workflow.

The causal impact workflow is fairly linear and can be broadly represented as

1. check user provided inputs (happens in analysis.py)
2. fit the model (happens in model.py)
3. make the predictions (happens in inferences.py)
4. format, visualise and summarise the output (happens back in analysis.py)

The model fitting is handled by statsmodels.tsa.structural.UnobservedComponents. The plotting is handled using matplotlib

Submit an issue

Before you work on any non-trivial code contribution it's best to first create a report in the issue tracker to start a discussion on the subject. This often provides additional considerations and avoids unnecessary work.

Create an environment

Before you start coding, we recommend creating an isolated to avoid any problems with your installed Python packages. We recommend using vscode's devcontainers

Clone the repository

1. Create an user account on GitHub if you do not already have one.

2. Fork the project repository: click on the Fork button near the top of the page. This creates a copy of the code under your account on GitHub.

3. Clone this copy to your local disk:

   git clone [email protected]:YourLogin/causalimpact.git
   cd causalimpact
   

4. You should run:

   pip install -e .
   

   to be able to import the package under development in the Python REPL.

5. Install pre-commit:

   pip install pre-commit
   pre-commit install
   

   causalimpact comes with a lot of hooks configured to automatically help the developer to check the code being written.

Implement your changes

1. Create a branch to hold your changes:

   git checkout -b my-feature
   

   and start making changes. Never work on the main branch!

2. Start your work on this branch. Don't forget to add docstrings to new functions, modules and classes, especially if they are part of public APIs.

3. Add yourself to the list of contributors in AUTHORS.md.

4. When you're done editing, do:

   git add <MODIFIED FILES>
   git commit
   

   to record your changes in git.

   Please make sure to see the validation messages from pre-commit_ and fix any eventual issues. This should automatically use flake8/black to check/fix the code style in a way that is compatible with the project.

   Important >
   Don't forget to add unit tests and documentation in case your contribution adds an additional feature and is not just a bugfix.

   Writing a descriptive commit message is highly recommended.

5. Please check that your changes don't break any unit tests with:

   tox
   

   (after having installed tox_ with pip install tox or pipx).

   You can also use tox_ to run several other pre-configured tasks in the repository. Try tox -av to see a list of the available checks.

Submit your contribution

1. If everything works fine, push your local branch to GitHub with:

   git push -u origin my-feature
   

2. Go to the web page of your fork and click "Create pull request" to send your changes for review.

   Find more detailed information in creating a PR. You might also want to open the PR as a draft first and mark it as ready for review after the feedbacks from the continuous integration (CI) system or any required fixes. :::

Troubleshooting

The following tips can be used when facing problems to build or test the package:

1. Make sure to fetch all the tags from the upstream repository. The command git describe --abbrev=0 --tags should return the version you are expecting. If you are trying to run CI scripts in a fork repository, make sure to push all the tags. You can also try to remove all the egg files or the complete egg folder, i.e., .eggs, as well as the *.egg-info folders in the src folder or potentially in the root of your project.

2. Sometimes tox_ misses out when new dependencies are added, especially to setup.cfg. If you find any problems with missing dependencies when running a command with tox_, try to recreate the tox environment using the -r flag. For example, instead of:

   tox -e build
   

   Try running:

   tox -r -e build
   

3. Make sure to have a reliable tox_ installation that uses the correct Python version (e.g., 3.7+). When in doubt you can run:

   tox --version
   # OR
   which tox
   

   If you have trouble and are seeing weird errors upon running tox_, you can also try to create a dedicated virtual environment with a tox_ binary freshly installed. For example:

   virtualenv .venv
   source .venv/bin/activate
   .venv/bin/pip install tox
   .venv/bin/tox -e all
   

4. Pytest can drop you in an interactive session in the case an error occurs. In order to do that you need to pass a --pdb option (for example by running tox -- -k <NAME OF THE FALLING TEST> --pdb). You can also setup breakpoints manually instead of using the --pdb option.

Maintainer tasks

Releases

If you are part of the group of maintainers and have correct user permissions on PyPI, the following steps can be used to release a new version for causalimpact:

1. Make sure all unit tests are successful locally and on CI.
2. Run cz bump --changelog to generate a new tag and an updated changelog.md file
3. Push the new tag to the upstream repository, e.g., git push upstream v1.2.3
4. The github action should detect the new tag and publish to pypi