File: HACKING.rst

package info (click to toggle)
cloud-init 20.2-2
  • links: PTS, VCS
  • area: main
  • in suites: bullseye, sid
  • size: 7,060 kB
  • sloc: python: 69,581; sh: 3,915; makefile: 105; xml: 21
file content (251 lines) | stat: -rw-r--r-- 9,179 bytes parent folder | download | duplicates (3)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
*********************
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.

Do these things once
====================

* To contribute, 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 'Josh Powers'.

  * 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 `Josh
    Powers <mailto:josh.powers@canonical.com>`_ with the subject,
    "Cloud-Init CLA"

  * You also may contact user ``powersj`` 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.

.. _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

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``)

.. _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

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.