.. _coding-style: ================= Salt Coding Style ================= To make it easier to contribute and read Salt code, SaltStack has `adopted Black `_ as its code formatter. There are a few places where Black is silent, and this guide should be used in those cases. Coding style is NEVER grounds to reject code contributions, and is never grounds to talk down to another member of the community (There are no grounds to treat others without respect, especially people working to improve Salt)! .. _pylint-instructions: Linting ======= Most Salt style conventions are codified in Salt's ``.testing.pylintrc`` file. Salt's pylint file has two dependencies: pylint_ and saltpylint_. You can install these dependencies with ``pip``: .. code-block:: bash pip install pylint pip install saltpylint The ``.testing.pylintrc`` file is found in the root of the Salt project and can be passed as an argument to the pylint_ program as follows: .. code-block:: bash pylint --rcfile=/path/to/salt/.testing.pylintrc salt/dir/to/lint .. note:: There are two pylint files in the ``salt`` directory. One is the ``.pylintrc`` file and the other is the ``.testing.pylintrc`` file. The tests that run in Jenkins against GitHub Pull Requests use ``.testing.pylintrc``. The ``testing.pylintrc`` file is a little less strict than the ``.pylintrc`` and is used to make it easier for contributors to submit changes. The ``.pylintrc`` file can be used for linting, but the ``testing.pylintrc`` is the source of truth when submitting pull requests. .. _pylint: http://www.pylint.org .. _saltpylint: https://github.com/saltstack/salt-pylint Variables ========= Variables should be a minimum of three characters and should provide an easy-to-understand name of the object being represented. When keys and values are iterated over, descriptive names should be used to represent the temporary variables. Multi-word variables should be separated by an underscore. Variables which are two-letter words should have an underscore appended to them to pad them to three characters. Formatting Strings ------------------ All strings which require formatting should use the `.format` string method: .. code-block:: python data = 'some text' more = '{0} and then some'.format(data) Make sure to use indices or identifiers in the format brackets, since empty brackets are not supported by python 2.6. Please do NOT use printf formatting. Docstring Conventions --------------------- When adding a new function or state, where possible try to use a ``versionadded`` directive to denote when the function, state, or parameter was added. .. code-block:: python def new_func(msg=''): ''' .. versionadded:: 0.16.0 Prints what was passed to the function. msg : None The string to be printed. ''' print(msg) If you are uncertain what version should be used, either consult a core developer in IRC or bring this up when opening your :ref:`pull request ` and a core developer will let you know what version to add. Typically this will be the next element in the `periodic table `_. Similar to the above, when an existing function or state is modified (for example, when an argument is added), then under the explanation of that new argument a ``versionadded`` directive should be used to note the version in which the new argument was added. If an argument's function changes significantly, the ``versionchanged`` directive can be used to clarify this: .. code-block:: python def new_func(msg='', signature=''): ''' .. versionadded:: 0.16.0 Prints what was passed to the function. msg : None The string to be printed. Will be prepended with 'Greetings! '. .. versionchanged:: 0.17.1 signature : None An optional signature. .. versionadded 0.17.0 ''' print('Greetings! {0}\n\n{1}'.format(msg, signature)) Dictionaries ============ Dictionaries should be initialized using `{}` instead of `dict()`. See here_ for an in-depth discussion of this topic. .. _here: http://doughellmann.com/2012/11/12/the-performance-impact-of-using-dict-instead-of-in-cpython-2-7-2.html Imports ======= Salt code prefers importing modules and not explicit functions. This is both a style and functional preference. The functional preference originates around the fact that the module import system used by pluggable modules will include callable objects (functions) that exist in the direct module namespace. This is not only messy, but may unintentionally expose code python libs to the Salt interface and pose a security problem. To say this more directly with an example, this is `GOOD`: .. code-block:: python import os def minion_path(): path = os.path.join(self.opts['cachedir'], 'minions') return path This on the other hand is `DISCOURAGED`: .. code-block:: python from os.path import join def minion_path(): path = join(self.opts['cachedir'], 'minions') return path The time when this is changed is for importing exceptions, generally directly importing exceptions is preferred: This is a good way to import exceptions: .. code-block:: python from salt.exceptions import CommandExecutionError Absolute Imports ---------------- Although `absolute imports`_ seems like an awesome idea, please do not use it. Extra care would be necessary all over salt's code in order for absolute imports to work as supposed. Believe it, it has been tried before and, as a tried example, by renaming ``salt.modules.sysmod`` to ``salt.modules.sys``, all other salt modules which needed to import :mod:`sys` would have to also import :mod:`absolute_import`, which should be avoided. .. note:: An exception to this rule is the ``absolute_import`` from ``__future__`` at the top of each file within the Salt project. This import is necessary for Py3 compatibility. This particular import looks like this: .. code-block:: python from __future__ import absolute_import This import is required for all new Salt files and is a good idea to add to any custom states or modules. However, the practice of avoiding absolute imports still applies to all other cases as to avoid a name conflict. .. _`absolute imports`: http://legacy.python.org/dev/peps/pep-0328/#rationale-for-absolute-imports Code Churn ========== Many pull requests have been submitted that only churn code in the name of PEP 8. Code churn is a leading source of bugs and is **strongly discouraged**. While style fixes are encouraged they should be isolated to a single file per commit, and the changes should be legitimate, if there are any questions about whether a style change is legitimate please reference this document and the official PEP 8 (http://legacy.python.org/dev/peps/pep-0008/) document before changing code. Many claims that a change is PEP 8 have been invalid, please double check before committing fixes. .. _`SEP 15`: https://github.com/saltstack/salt-enhancement-proposals/pull/21