Source code for wemake_python_styleguide.violations.base

Contains detailed technical information about :term:`violation` internals.

.. _violations:

Violations API

.. currentmodule:: wemake_python_styleguide.violations.base

.. autoclasstree:: wemake_python_styleguide.violations.base

.. autosummary::


Violation cannot have more than one base class.
See :ref:`tutorial` for more information about choosing a correct base class.


- Each violation class name should end with "Violation"
- Each violation must have a long docstring with full description
- Each violation must have "Reasoning" and "Solution" sections
- Each violation must have "versionadded" policy
- Each violation should have an example with correct and wrong usages
- If violation error template should have a parameter
  it should be the last part of the text: ``: {0}``

Deprecating a violation

When you want to mark some violation as deprecated,
then assign ``deprecated`` boolean flag to it:

.. code:: python

  class SomeViolation(ASTViolation):
      deprecated = True



import abc
import ast
import enum
import tokenize
from typing import Callable, ClassVar, Optional, Set, Tuple, Union

from typing_extensions import final

#: General type for all possible nodes where error happens.
ErrorNode = Union[

#: We use this type to define helper classes with callbacks to add violations.
ErrorCallback = Callable[['BaseViolation'], None]

[docs]@enum.unique class ViolationPostfixes(enum.Enum): """String values of postfixes used for violation baselines.""" bigger_than = ' > {0}' less_than = ' < {0}'
[docs]class BaseViolation(object, metaclass=abc.ABCMeta): """ Abstract base class for all style violations. It basically just defines how to create any error and how to format this error later on. Each subclass must define ``error_template`` and ``code`` fields. Attributes: error_template: message that will be shown to user after formatting. code: unique violation number. Used to identify the violation. previous_codes: just a documentation thing to track changes in time. deprecated: indicates that this violation will be removed soon. postfix_template: indicates message that we show at the very end. """ error_template: ClassVar[str] code: ClassVar[int] previous_codes: ClassVar[Set[int]] deprecated: ClassVar[bool] = False # We use this code to show base metrics and thresholds mostly: postfix_template: ClassVar[ViolationPostfixes] = ( ViolationPostfixes.bigger_than ) def __init__( self, node: ErrorNode, text: Optional[str] = None, baseline: Optional[int] = None, ) -> None: """ Creates a new instance of an abstract violation. Arguments: node: violation was raised by this node. If applicable. text: extra text to format the final message. If applicable. baseline: some complexity violations show the logic threshold here. """ self._node = node self._text = text self._baseline = baseline
[docs] @final def message(self) -> str: """ Returns error's formatted message with code and reason. Conditionally formats the ``error_template`` if it is required. """ return '{0} {1}{2}'.format( self._full_code(), self.error_template.format(self._text), self._postfix_information(), )
[docs] @final def node_items(self) -> Tuple[int, int, str]: """Returns tuple to match ``flake8`` API format.""" return (*self._location(), self.message())
@final def _full_code(self) -> str: """ Returns fully formatted code. Adds violation letter to the numbers. Also ensures that codes like ``3`` will be represented as ``WPS003``. """ return 'WPS{0}'.format(str(self.code).zfill(3)) @final def _postfix_information(self) -> str: """ Adds useful information to the end of the violation message. Useful for complexity baselines and other thresholds. """ if self._baseline is None: return '' return self.postfix_template.value.format(self._baseline) @abc.abstractmethod def _location(self) -> Tuple[int, int]: """Base method for showing error location."""
class _BaseASTViolation(BaseViolation, metaclass=abc.ABCMeta): """Used as a based type for all ``ast`` violations.""" _node: Optional[ast.AST] @final def _location(self) -> Tuple[int, int]: line_number = getattr(self._node, 'lineno', 0) column_offset = getattr(self._node, 'col_offset', 0) return line_number, column_offset
[docs]class ASTViolation(_BaseASTViolation, metaclass=abc.ABCMeta): """Violation for ``ast`` based style visitors.""" _node: ast.AST
[docs]class MaybeASTViolation(_BaseASTViolation, metaclass=abc.ABCMeta): """ Violation for ``ast`` and modules visitors. Is used for violations that share the same rule for nodes and module names. Is wildly used for naming rules. """ def __init__( self, node: Optional[ast.AST] = None, text: Optional[str] = None, baseline: Optional[int] = None, ) -> None: """Creates new instance of module violation without explicit node.""" super().__init__(node, text=text, baseline=baseline)
[docs]class TokenizeViolation(BaseViolation, metaclass=abc.ABCMeta): """Violation for ``tokenize`` based visitors.""" _node: tokenize.TokenInfo @final def _location(self) -> Tuple[int, int]: return self._node.start
[docs]class SimpleViolation(BaseViolation, metaclass=abc.ABCMeta): """Violation for cases where there's no associated nodes.""" _node: None def __init__( self, node=None, text: Optional[str] = None, baseline: Optional[int] = None, ) -> None: """Creates new instance of simple style violation.""" super().__init__(node, text=text, baseline=baseline) @final def _location(self) -> Tuple[int, int]: """ Return violation location inside the file. Default location is in the so-called "file beginning". Cannot be ignored by inline ``noqa`` comments. """ return 0, 0