********************* Hacking on cloud-init ********************* This document describes how to contribute changes to cloud-init. It assumes you have a `GitHub`_ account, and refers to your GitHub user as ``GH_USER`` throughout. Submitting your first pull request ================================== Follow these steps to submit your first pull request to cloud-init: * To contribute to cloud-init, you must sign the Canonical `contributor license agreement`_ * If you have already signed it as an individual, your Launchpad user will be listed in the `contributor-agreement-canonical`_ group. (Unfortunately there is no easy way to check if an organization or company you are doing work for has signed.) * When signing it: * ensure that you fill in the GitHub username field. * when prompted for 'Project contact' or 'Canonical Project Manager', enter 'Rick Harding'. * If your company has signed the CLA for you, please contact us to help in verifying which Launchpad/GitHub accounts are associated with the company. * For any questions or help with the process, please email `Rick Harding `_ with the subject, "Cloud-Init CLA" * You also may contact user ``rick_h`` in the ``#cloud-init`` channel on the Freenode IRC network. * Configure git with your email and name for commit messages. Your name will appear in commit messages and will also be used in changelogs or release notes. Give yourself credit!:: git config user.name "Your Name" git config user.email "Your Email" * Sign into your `GitHub`_ account * Fork the upstream `repository`_ on Github and clicking on the ``Fork`` button * Create a new remote pointing to your personal GitHub repository. .. code:: sh git clone git://github.com/canonical/cloud-init cd cloud-init git remote add GH_USER git@github.com:GH_USER/cloud-init.git git push GH_USER master * Read through the cloud-init `Code Review Process`_, so you understand how your changes will end up in cloud-init's codebase. * Submit your first cloud-init pull request, adding yourself to the in-repository list that we use to track CLA signatures: `tools/.github-cla-signers`_ * See `PR #344`_ and `PR #345`_ for examples of what this pull request should look like. * (If you already have a change that you want to submit, you can also include the change to ``tools/.github-cla-signers`` in that pull request, there is no need for two separate PRs.) .. _GitHub: https://github.com .. _Launchpad: https://launchpad.net .. _repository: https://github.com/canonical/cloud-init .. _contributor license agreement: https://ubuntu.com/legal/contributors .. _contributor-agreement-canonical: https://launchpad.net/%7Econtributor-agreement-canonical/+members .. _tools/.github-cla-signers: https://github.com/canonical/cloud-init/blob/master/tools/.github-cla-signers .. _PR #344: https://github.com/canonical/cloud-init/pull/344 .. _PR #345: https://github.com/canonical/cloud-init/pull/345 Transferring CLA Signatures from Launchpad to Github ---------------------------------------------------- For existing contributors who have signed the agreement in Launchpad before the Github username field was included, we need to verify the link between your `Launchpad`_ account and your `GitHub`_ account. To enable us to do this, we ask that you create a branch with both your Launchpad and GitHub usernames against both the Launchpad and GitHub cloud-init repositories. We've added a tool (``tools/migrate-lp-user-to-github``) to the cloud-init repository to handle this migration as automatically as possible. The cloud-init team will review the two merge proposals and verify that the CLA has been signed for the Launchpad user and record the associated GitHub account. Do these things for each feature or bug ======================================= * Create a new topic branch for your work:: git checkout -b my-topic-branch * Make and commit your changes (note, you can make multiple commits, fixes, more commits.):: git commit * Run unit tests and lint/formatting checks with `tox`_:: tox * Push your changes to your personal GitHub repository:: git push -u GH_USER my-topic-branch * Use your browser to create a merge request: - Open the branch on GitHub - You can see a web view of your repository and navigate to the branch at: ``https://github.com/GH_USER/cloud-init/tree/my-topic-branch`` - Click 'Pull Request` - Fill out the pull request title, summarizing the change and a longer message indicating important details about the changes included, like :: Activate the frobnicator. The frobnicator was previously inactive and now runs by default. This may save the world some day. Then, list the bugs you fixed as footers with syntax as shown here. The commit message should be one summary line of less than 74 characters followed by a blank line, and then one or more paragraphs describing the change and why it was needed. This is the message that will be used on the commit when it is sqaushed and merged into trunk. LP: #1 Note that the project continues to use LP: #NNNNN format for closing launchpad bugs rather than GitHub Issues. - Click 'Create Pull Request` Then, someone in the `Ubuntu Server`_ team will review your changes and follow up in the pull request. Look at the `Code Review Process`_ doc to understand the following steps. Feel free to ping and/or join ``#cloud-init`` on freenode irc if you have any questions. .. _tox: https://tox.readthedocs.io/en/latest/ .. _Ubuntu Server: https://github.com/orgs/canonical/teams/ubuntu-server .. _Code Review Process: https://cloudinit.readthedocs.io/en/latest/topics/code_review.html Design ====== This section captures design decisions that are helpful to know when hacking on cloud-init. Cloud Config Modules -------------------- * Any new modules should use underscores in any new config options and not hyphens (e.g. `new_option` and *not* `new-option`). Unit Testing ------------ cloud-init uses `pytest`_ to run its tests, and has tests written both as ``unittest.TestCase`` sub-classes and as un-subclassed pytest tests. The following guidelines should be followed: * For ease of organisation and greater accessibility for developers not familiar with pytest, all cloud-init unit tests must be contained within test classes * Put another way, module-level test functions should not be used * pytest test classes should use `pytest fixtures`_ to share functionality instead of inheritance * As all tests are contained within classes, it is acceptable to mix ``TestCase`` test classes and pytest test classes within the same test file * These can be easily distinguished by their definition: pytest classes will not use inheritance at all (e.g. `TestGetPackageMirrorInfo`_), whereas ``TestCase`` classes will subclass (indirectly) from ``TestCase`` (e.g. `TestPrependBaseCommands`_) * pytest tests should use bare ``assert`` statements, to take advantage of pytest's `assertion introspection`_ * For ``==`` and other commutative assertions, the expected value should be placed before the value under test: ``assert expected_value == function_under_test()`` * As we still support Ubuntu 16.04 (Xenial Xerus), we can only use pytest features that are available in v2.8.7. This is an inexhaustive list of ways in which this may catch you out: * Support for using ``yield`` in ``pytest.fixture`` functions was only introduced in `pytest 3.0`_. Such functions must instead use the ``pytest.yield_fixture`` decorator. * Only the following built-in fixtures are available [#fixture-list]_: * ``cache`` * ``capsys`` * ``capfd`` * ``record_xml_property`` * ``monkeypatch`` * ``pytestconfig`` * ``recwarn`` * ``tmpdir_factory`` * ``tmpdir`` * Variables/parameter names for ``Mock`` or ``MagicMock`` instances should start with ``m_`` to clearly distinguish them from non-mock variables * For example, ``m_readurl`` (which would be a mock for ``readurl``) * The ``assert_*`` methods that are available on ``Mock`` and ``MagicMock`` objects should be avoided, as typos in these method names may not raise ``AttributeError`` (and so can cause tests to silently pass). An important exception: if a ``Mock`` is `autospecced`_ then misspelled assertion methods *will* raise an ``AttributeError``, so these assertion methods may be used on autospecced ``Mock`` objects. For non-autospecced ``Mock`` s, these substitutions can be used (``m`` is assumed to be a ``Mock``): * ``m.assert_any_call(*args, **kwargs)`` => ``assert mock.call(*args, **kwargs) in m.call_args_list`` * ``m.assert_called()`` => ``assert 0 != m.call_count`` * ``m.assert_called_once()`` => ``assert 1 == m.call_count`` * ``m.assert_called_once_with(*args, **kwargs)`` => ``assert [mock.call(*args, **kwargs)] == m.call_args_list`` * ``m.assert_called_with(*args, **kwargs)`` => ``assert mock.call(*args, **kwargs) == m.call_args_list[-1]`` * ``m.assert_has_calls(call_list, any_order=True)`` => ``for call in call_list: assert call in m.call_args_list`` * ``m.assert_has_calls(...)`` and ``m.assert_has_calls(..., any_order=False)`` are not easily replicated in a single statement, so their use when appropriate is acceptable. * ``m.assert_not_called()`` => ``assert 0 == m.call_count`` * Test arguments should be ordered as follows: * ``mock.patch`` arguments. When used as a decorator, ``mock.patch`` partially applies its generated ``Mock`` object as the first argument, so these arguments must go first. * ``pytest.mark.parametrize`` arguments, in the order specified to the ``parametrize`` decorator. These arguments are also provided by a decorator, so it's natural that they sit next to the ``mock.patch`` arguments. * Fixture arguments, alphabetically. These are not provided by a decorator, so they are last, and their order has no defined meaning, so we default to alphabetical. * It follows from this ordering of test arguments (so that we retain the property that arguments left-to-right correspond to decorators bottom-to-top) that test decorators should be ordered as follows: * ``pytest.mark.parametrize`` * ``mock.patch`` * When there are multiple patch calls in a test file for the module it is testing, it may be desirable to capture the shared string prefix for these patch calls in a module-level variable. If used, such variables should be named ``M_PATH`` or, for datasource tests, ``DS_PATH``. .. _pytest: https://docs.pytest.org/ .. _pytest fixtures: https://docs.pytest.org/en/latest/fixture.html .. _TestGetPackageMirrorInfo: https://github.com/canonical/cloud-init/blob/42f69f410ab8850c02b1f53dd67c132aa8ef64f5/cloudinit/distros/tests/test_init.py\#L15 .. _TestPrependBaseCommands: https://github.com/canonical/cloud-init/blob/master/cloudinit/tests/test_subp.py#L9 .. _assertion introspection: https://docs.pytest.org/en/latest/assert.html .. _pytest 3.0: https://docs.pytest.org/en/latest/changelog.html#id1093 .. _autospecced: https://docs.python.org/3.8/library/unittest.mock.html#autospeccing Type Annotations ---------------- The cloud-init codebase uses Python's annotation support for storing type annotations in the style specified by `PEP-484`_. Their use in the codebase is encouraged but with one important caveat: types from the ``typing`` module cannot be used. cloud-init still supports Python 3.4, which doesn't have the ``typing`` module in the stdlib. This means that the use of any types from the ``typing`` module in the codebase would require installation of an additional Python module on platforms using Python 3.4. As such platforms are generally in maintenance mode, the introduction of a new dependency may act as a break in compatibility in practical terms. Similarly, only function annotations are appropriate for use, as the variable annotations specified in `PEP-526`_ were introduced in Python 3.6. .. _PEP-484: https://www.python.org/dev/peps/pep-0484/ .. _PEP-526: https://www.python.org/dev/peps/pep-0526/ .. [#fixture-list] This list of fixtures (with markup) can be reproduced by running:: py.test-3 --fixtures -q | grep "^[^ ]" | grep -v no | sed 's/.*/* ``\0``/' in a xenial lxd container with python3-pytest installed.