flake8-class-attributes-order

An extension for flake8 to report on wrong class attributes order and class level logic.

The validator can extract class attribute type: docstring, property, nested class, GLOBAL_VAR, etc. If django model fields are detected, the validator can detect, if the field is link to another table (foreign key, generic key, etc) or not.

After resolving each attribute type, validator checks attributes order.

Default configuration checks for the following order of attributes:

• __new__
• __init__
• __post_init__
• other magic methods
• @property
• @staticmethod
• @classmethod
• other methods
• protected methods
• private methods

If the order is broken, validator will report on it.

Besides methods, the validator checks other attributes methods: docstrings, nested classes, constants, attributes, and so on.

Also validator checks, if class has no class level logic and report if any. Here is an example:

class PhoneForm(forms.Form):
    phone = forms.CharField(17, label='Телефон'.upper())

    # this should happen in __init__!
    phone.widget.attrs.update({'class': 'form-control phone'})

Installation

pip install flake8-class-attributes-order

Configuration

Strict mode

There is another preconfigured order that is more strict on private subtypes:

• __new__
• __init__
• __post_init__
• other magic method
• @property
• @staticmethod
• @classmethod
• other methods
• protected @property
• protected @staticmethod
• protected @classmethod
• other protected methods
• private @property
• private @staticmethod
• private @classmethod
• other private methods

To enable strict validation, please set the flag in your config file:

[flake8]
use_class_attributes_order_strict_mode = True

Manual order configuration

Order can be manually configured via class_attributes_order config setting.

For example, if you prefer to put class Meta after constants and fields:

[flake8]
class_attributes_order =
    field,
    meta_class,
    nested_class,
    magic_method,
    property_method,
    static_method,
    class_method,
    method,
    protected_method,
    private_method

Configurable options:

Option	Description	Fallbacks to*
meta_class	class Meta: (e.g. in Django projects)	nested_class
nested_class	Other nested classes	None*
constant	SOME_CONSTANTS	field
outer_field	some = models.ForeignKey etc.	field
field	Other fields	None
protected field	Other field starting with _	field
private field	Other field starting with __	field
__new__	__new__	magic_method
__init__	__init__	magic_method
__post_init__	__post_init__	magic_method
__str__	__str__	magic_method
magic_method	Other magic methods	method
save	def save(...)	method
delete	def delete(...)	method
property_method	@property/@cached_property etc.	method
protected_property_method	@property/@cached_property etc. with _	property_method
private_property_method	@property/@cached_property with __	property_method
static_method	@staticmethod	method
protected_static_method	@staticmethod beginning with _	static_method
private_static_method	@staticmethod beginning with __	static_method
class_method	@classmethod	method
protected_class_method	@classmethod beginning with _	class_method
private_class_method	@classmethod beginning with __	class_method
private_method	other methods beginning with __	method
protected_method	other methods beginning with _	method
method	other methods	None

* if not provided, will use its supertype order

** if not defined, such base types and all their subtypes (unless defined) will be ignored during validation. It's recommended to set at least nested_class, field and method

You choose how detailed your configuration is. For example, you can define order of each supported magic method (__new__, __str__, etc.), or set magic_method to allow any order among them or even just use method

Example

DEBUG = True


class User:
    def fetch_info_from_crm(self):
        pass

    LOGIN_FIELD = 'email'  # wtf? this should be on top of class definition!


class UserNode:
    class Meta:
        model = User

    if DEBUG:  # not great idea at all
        def is_synced_with_crm(self):
            pass

Usage:

$ flake8 test.py
test.py:5:5: CCE001 User.fetch_info_from_crm should be after User.LOGIN_FIELD
test.py:15:5: CCE002 Class level expression detected model UserNode, line 15

Tested on Python 3.7.x and flake8 3.7.5.

Error codes

Error code	Description
CCE001	Wrong class attributes order (XXX should be after YYY)
CCE002	Class level expression detected

Contributing

We would love you to contribute to our project. It's simple:

• Create an issue with bug you found or proposal you have. Wait for approve from maintainer.
• Create a pull request. Make sure all checks are green.
• Fix review comments if any.
• Be awesome.

Here are useful tips:

• You can run all checks and tests with make check. Please do it before TravisCI does.
• We use BestDoctor python styleguide.
• We respect Django CoC. Make soft, not bullshit.