How to contribute to Flask

Thank you for considering contributing to Flask!

Support questions

Please, don't use the issue tracker for this. Use one of the following resources for questions about your own code:

• The #get-help channel on our Discord chat: https://discord.gg/t6rrQZH
  • The IRC channel #pocoo on FreeNode is linked to Discord, but Discord is preferred.
• The mailing list flask@python.org for long term discussion or larger issues.
• Ask on Stack Overflow. Search with Google first using: site:stackoverflow.com flask {search term, exception message, etc.}

Reporting issues

• Describe what you expected to happen.
• If possible, include a minimal reproducible example to help us identify the issue. This also helps check that the issue is not with your own code.
• Describe what actually happened. Include the full traceback if there was an exception.
• List your Python, Flask, and Werkzeug versions. If possible, check if this issue is already fixed in the repository.

Submitting patches

• Use Black to autoformat your code. This should be done for you as a Git pre-commit hook, set up below. You may also wish to use Black's Editor integration.
• Include tests if your patch is supposed to solve a bug, and explain clearly under which circumstances the bug happens. Make sure the test fails without your patch.
• Include a string like "Fixes #123" in your commit message (where 123 is the issue you fixed). See Closing issues using keywords.

First time setup

• Download and install the latest version of git.

• Configure git with your username and email.

  $ git config --global user.name 'your name'
  $ git config --global user.email 'your email'
  

• Make sure you have a GitHub account.

• Fork Flask to your GitHub account by clicking the Fork button.

• Clone your GitHub fork locally.

  $ git clone https://github.com/{username}/flask
  $ cd flask
  

• Add the main repository as a remote to update later:

  .. code-block:: text
  

  git remote add pallets https://github.com/pallets/flask git fetch pallets

• Create a virtualenv.

  $ python3 -m venv env
  $ . env/bin/activate
  

  On Windows, activating is different.

  > env\Scripts\activate
  

• Install Flask in editable mode with development dependencies.

  $ pip install -e . -r requirements/dev.txt
  

• Install the pre-commit hooks.

  $ pre-commit install
  

Start coding

• Create a branch to identify the issue you would like to work on. If you're submitting a bug or documentation fix, branch off of the latest ".x" branch.

  $ git checkout -b your-branch-name origin/1.0.x
  

  If you're submitting a feature addition or change, branch off of the "master" branch.

  $ git checkout -b your-branch-name origin/master
  

• Using your favorite editor, make your changes, committing as you go.

• Include tests that cover any code changes you make. Make sure the test fails without your patch. Run the tests.

• Push your commits to GitHub and create a pull request.

  $ git push --set-upstream origin your-branch-name
  

Running the tests

Run the basic test suite with pytest.

$ pytest

This only runs the tests for the current environment. Whether this is relevant depends on which part of Flask you're working on. CI will run the full suite when you submit your pull request.

The full test suite takes a long time to run because it tests multiple combinations of Python and dependencies. If you don't have a Python version installed, it will be skipped with a warning message at the end.

$ tox

Running test coverage

Generating a report of lines that do not have test coverage can indicate where to start contributing. Run pytest using coverage and generate a report on the terminal and as an interactive HTML document.

$ coverage run -m pytest
$ coverage report
$ coverage html  # then open htmlcov/index.html

Read more about coverage.

Running the full test suite with tox will combine the coverage reports from all runs.

Building the docs

Build the docs in the docs directory using Sphinx.

$ cd docs
$ make html

Open _build/html/index.html in your browser to view the docs.

Read more about Sphinx.

Caution: zero-padded file modes

This repository contains several zero-padded file modes that may cause issues when pushing this repository to Git hosts other than GitHub. Fixing this is destructive to the commit history, so we suggest ignoring these warnings. If it fails to push and you're using a self-hosted Git service like GitLab, you can turn off repository checks in the admin panel.

These files can also cause issues while cloning if you have fsckObjects enabled with either of the following in your git config.

[fetch]
fsckObjects = true

[receive]
fsckObjects = true

The only solution is to set both of the above to false, clone, and then set them back to true after.