doc/topics/development/conventions/style.rst
.. _coding-style:
To make it easier to contribute and read Salt code, SaltStack has adopted Black <SEP 15_>_ 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:
Most Salt style conventions are codified in Salt's .pylintrc file.
Salt's linting has two major dependencies: pylint_ and saltpylint_, the full lint
requirements can be found under requirements/static/ci/lint.in and the pinned
requirements at requirements/static/ci/py3.<minor-version>/lint.txt, however,
linting should be done using :ref:nox <getting_set_up_for_tests>, which is how
pull requests are checked.
.. code-block:: bash
nox -e lint
One can target either salt's source code or the test suite(different pylint rules apply):
.. code-block:: bash
nox -e lint-salt nox -e lint-tests
.. _pylint: https://www.pylint.org/ .. _saltpylint: https://github.com/saltstack/salt-pylint
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.
All strings which require formatting should use the .format string method:
Please do NOT use printf formatting, unless it's a log message.
Good:
.. code-block:: python
data = "some text"
more = "{} and then some".format(data)
log.debug("%s and then some", data)
Bad:
.. code-block:: python
data = "some text"
log.debug("{} and then some".format(data))
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 the Community Discord or bring this up when opening your :ref:pull request <installing-for-development> and a core developer will let you know what
version to add. Typically this will be the next element in the periodic table <https://en.wikipedia.org/wiki/List_of_chemical_elements>_.
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 should be initialized using {} instead of dict().
See here_ for an in-depth discussion of this topic.
.. _here: https://doughellmann.com/posts/the-performance-impact-of-using-dict-instead-of-in-cpython-2-7-2/
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
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<python2:sys> would have to
also import :mod:absolute_import<python2:__future__>, 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: https://legacy.python.org/dev/peps/pep-0328/#rationale-for-absolute-imports
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 (https://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