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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)!

Linting¶

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 nox, which is how pull requests are checked.

nox -e lint

One can target either salt's source code or the test suite(different pylint rules apply):

nox -e lint-salt
nox -e lint-tests

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:

Please do NOT use printf formatting, unless it's a log message.

Good:

data = "some text"
more = "{} and then some".format(data)
log.debug("%s and then some", data)

Bad:

data = "some text"
log.debug("{} and then some".format(data))

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.

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 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:

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.

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:

import os


def minion_path():
    path = os.path.join(self.opts["cachedir"], "minions")
    return path

This on the other hand is DISCOURAGED:

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:

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 sys would have to also import 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:

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.

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 (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.