Optional Pylint checkers in the extensions module
*************************************************

Pylint provides the following optional plugins:

* Deprecated Builtins checker

* Broad Try Clause checker

* Else If Used checker

* Code Style checker

* Compare-To-Zero checker

* Comparison-Placement checker

* Confusing Elif checker

* Consider Ternary Expression checker

* Parameter Documentation checker

* Docstyle checker

* Refactoring checker

* Compare-To-Empty-String checker

* Consider-Using-Any-Or-All checker

* Design checker

* Overlap-Except checker

* Multiple Types checker

* Set Membership checker

* Typing checker

* While Used checker

You can activate any or all of these extensions by adding a "load-
plugins" line to the "MASTER" section of your ".pylintrc", for
example:

   load-plugins=pylint.extensions.docparams,pylint.extensions.docstyle


Broad Try Clause checker
========================

This checker is provided by "pylint.extensions.broad_try_clause".
Verbatim name of the checker is "broad_try_clause".


Broad Try Clause checker Options
--------------------------------

max-try-statements:
   Maximum number of statements allowed in a try clause

   Default: "1"


Broad Try Clause checker Messages
---------------------------------

too-many-try-statements (W0717):
   Try clause contains too many statements.


Code Style checker
==================

This checker is provided by "pylint.extensions.code_style". Verbatim
name of the checker is "code_style".


Code Style checker Documentation
--------------------------------

Checkers that can improve code consistency. As such they don't
necessarily provide a performance benefit and are often times
opinionated.


Code Style checker Options
--------------------------

max-line-length-suggestions:
   Max line length for which to sill emit suggestions. Used to prevent
   optional suggestions which would get split by a code formatter
   (e.g., black). Will default to the setting for "max-line-length".


Code Style checker Messages
---------------------------

consider-using-tuple (R6102):
   *Consider using an in-place tuple instead of list* Only for style
   consistency! Emitted where an in-place defined "list" can be
   replaced by a "tuple". Due to optimizations by CPython, there is no
   performance benefit from it.

consider-using-namedtuple-or-dataclass (R6101):
   *Consider using namedtuple or dataclass for dictionary values*
   Emitted when dictionary values can be replaced by namedtuples or
   dataclass instances.

consider-using-assignment-expr (R6103):
   *Use '%s' instead* Emitted when an if assignment is directly
   followed by an if statement and both can be combined by using an
   assignment expression ":=". Requires Python 3.8 and "py-version >=
   3.8".


Compare-To-Empty-String checker
===============================

This checker is provided by "pylint.extensions.emptystring". Verbatim
name of the checker is "compare-to-empty-string".


Compare-To-Empty-String checker Messages
----------------------------------------

compare-to-empty-string (C1901):
   *Avoid comparisons to empty string* Used when Pylint detects
   comparison to an empty string constant.


Compare-To-Zero checker
=======================

This checker is provided by "pylint.extensions.comparetozero".
Verbatim name of the checker is "compare-to-zero".


Compare-To-Zero checker Messages
--------------------------------

compare-to-zero (C2001):
   *Avoid comparisons to zero* Used when Pylint detects comparison to
   a 0 constant.


Comparison-Placement checker
============================

This checker is provided by "pylint.extensions.comparison_placement".
Verbatim name of the checker is "comparison-placement".


Comparison-Placement checker Messages
-------------------------------------

misplaced-comparison-constant (C2201):
   *Comparison should be %s* Used when the constant is placed on the
   left side of a comparison. It is usually clearer in intent to place
   it in the right hand side of the comparison.


Confusing Elif checker
======================

This checker is provided by "pylint.extensions.confusing_elif".
Verbatim name of the checker is "confusing_elif".


Confusing Elif checker Messages
-------------------------------

confusing-consecutive-elif (R5601):
   *Consecutive elif with differing indentation level, consider
   creating a function to separate the inner elif* Used when an elif
   statement follows right after an indented block which itself ends
   with if or elif. It may not be ovious if the elif statement was
   willingly or mistakenly unindented. Extracting the indented if
   statement into a separate function might avoid confusion and
   prevent errors.


Consider-Using-Any-Or-All checker
=================================

This checker is provided by "pylint.extensions.for_any_all". Verbatim
name of the checker is "consider-using-any-or-all".


Consider-Using-Any-Or-All checker Messages
------------------------------------------

consider-using-any-or-all (C0501):
   *`for` loop could be `%s`* A for loop that checks for a condition
   and return a bool can be replaced with any or all.


Consider Ternary Expression checker
===================================

This checker is provided by
"pylint.extensions.consider_ternary_expression". Verbatim name of the
checker is "consider_ternary_expression".


Consider Ternary Expression checker Messages
--------------------------------------------

consider-ternary-expression (W0160):
   *Consider rewriting as a ternary expression* Multiple assign
   statements spread across if/else blocks can be rewritten with a
   single assignment and ternary expression


Deprecated Builtins checker
===========================

This checker is provided by "pylint.extensions.bad_builtin". Verbatim
name of the checker is "deprecated_builtins".


Deprecated Builtins checker Documentation
-----------------------------------------

This used to be the "bad-builtin" core checker, but it was moved to an
extension instead. It can be used for finding prohibited used
builtins, such as "map" or "filter", for which other alternatives
exists.

If you want to control for what builtins the checker should warn
about, you can use the "bad-functions" option:

   $ pylint a.py --load-plugins=pylint.extensions.bad_builtin --bad-functions=apply,reduce
   ...


Deprecated Builtins checker Options
-----------------------------------

bad-functions:
   List of builtins function names that should not be used, separated
   by a comma

   Default: "map,filter"


Deprecated Builtins checker Messages
------------------------------------

bad-builtin (W0141):
   *Used builtin function %s* Used when a disallowed builtin function
   is used (see the bad-function option). Usual disallowed functions
   are the ones like map, or filter , where Python offers now some
   cleaner alternative like list comprehension.


Design checker
==============

This checker is provided by "pylint.extensions.mccabe". Verbatim name
of the checker is "design".


Design checker Documentation
----------------------------

You can now use this plugin for finding complexity issues in your code
base.

Activate it through "pylint --load-plugins=pylint.extensions.mccabe".
It introduces a new warning, "too-complex", which is emitted when a
code block has a complexity higher than a preestablished value, which
can be controlled through the "max-complexity" option, such as in this
example:

   $ cat a.py
   def f10():
       """McCabe rating: 11"""
       myint = 2
       if myint == 5:
           return myint
       elif myint == 6:
           return myint
       elif myint == 7:
           return myint
       elif myint == 8:
           return myint
       elif myint == 9:
           return myint
       elif myint == 10:
           if myint == 8:
               while True:
                   return True
           elif myint == 8:
               with myint:
                   return 8
       else:
           if myint == 2:
               return myint
           return myint
       return myint
   $ pylint a.py --load-plugins=pylint.extensions.mccabe
   R:1: 'f10' is too complex. The McCabe rating is 11 (too-complex)
   $ pylint a.py --load-plugins=pylint.extensions.mccabe --max-complexity=50
   $


Design checker Options
----------------------

max-complexity:
   McCabe complexity cyclomatic threshold

   Default: "10"


Design checker Messages
-----------------------

too-complex (R1260):
   *%s is too complex. The McCabe rating is %d* Used when a method or
   function is too complex based on McCabe Complexity Cyclomatic


Docstyle checker
================

This checker is provided by "pylint.extensions.docstyle". Verbatim
name of the checker is "docstyle".


Docstyle checker Messages
-------------------------

bad-docstring-quotes (C0198):
   *Bad docstring quotes in %s, expected """, given %s* Used when a
   docstring does not have triple double quotes.

docstring-first-line-empty (C0199):
   *First line empty in %s docstring* Used when a blank line is found
   at the beginning of a docstring.


Else If Used checker
====================

This checker is provided by "pylint.extensions.check_elif". Verbatim
name of the checker is "else_if_used".


Else If Used checker Messages
-----------------------------

else-if-used (R5501):
   *Consider using "elif" instead of "else if"* Used when an else
   statement is immediately followed by an if statement and does not
   contain statements that would be unrelated to it.


Multiple Types checker
======================

This checker is provided by
"pylint.extensions.redefined_variable_type". Verbatim name of the
checker is "multiple_types".


Multiple Types checker Messages
-------------------------------

redefined-variable-type (R0204):
   *Redefinition of %s type from %s to %s* Used when the type of a
   variable changes inside a method or a function.


Overlap-Except checker
======================

This checker is provided by
"pylint.extensions.overlapping_exceptions". Verbatim name of the
checker is "overlap-except".


Overlap-Except checker Messages
-------------------------------

overlapping-except (W0714):
   *Overlapping exceptions (%s)* Used when exceptions in handler
   overlap or are identical


Parameter Documentation checker
===============================

This checker is provided by "pylint.extensions.docparams". Verbatim
name of the checker is "parameter_documentation".


Parameter Documentation checker Documentation
---------------------------------------------

If you document the parameters of your functions, methods and
constructors and their types systematically in your code this optional
component might be useful for you. Sphinx style, Google style, and
Numpy style are supported. (For some examples, see
https://pypi.python.org/pypi/sphinxcontrib-napoleon .)

You can activate this checker by adding the line:

   load-plugins=pylint.extensions.docparams

to the "MASTER" section of your ".pylintrc".

This checker verifies that all function, method, and constructor
docstrings include documentation of the

* parameters and their types

* return value and its type

* exceptions raised

and can handle docstrings in

* Sphinx style ("param", "type", "return", "rtype", "raise" /
  "except"):

     def function_foo(x, y, z):
         '''function foo ...

         :param x: bla x
         :type x: int

         :param y: bla y
         :type y: float

         :param int z: bla z

         :return: sum
         :rtype: float

         :raises OSError: bla
         '''
         return x + y + z

* or the Google style ("Args:", "Returns:", "Raises:"):

     def function_foo(x, y, z):
         '''function foo ...

         Args:
             x (int): bla x
             y (float): bla y

             z (int): bla z

         Returns:
             float: sum

         Raises:
             OSError: bla
         '''
         return x + y + z

* or the Numpy style ("Parameters", "Returns", "Raises"):

     def function_foo(x, y, z):
         '''function foo ...

         Parameters
         ----------
         x: int
             bla x
         y: float
             bla y

         z: int
             bla z

         Returns
         -------
         float
             sum

         Raises
         ------
         OSError
             bla
         '''
         return x + y + z

You'll be notified of **missing parameter documentation** but also of
**naming inconsistencies** between the signature and the documentation
which often arise when parameters are renamed automatically in the
code, but not in the documentation. **Note:** by default docstrings of
private and magic methods are not checked. To change this behaviour
(for example, to also check "__init__") add "no-docstring-
rgx=^(?!__init__$)_" to the "BASIC" section of your ".pylintrc".

Constructor parameters can be documented in either the class docstring
or the "__init__" docstring, but not both:

   class ClassFoo(object):
       '''Sphinx style docstring foo

       :param float x: bla x

       :param y: bla y
       :type y: int
       '''
       def __init__(self, x, y):
           pass

   class ClassBar(object):
       def __init__(self, x, y):
           '''Google style docstring bar

           Args:
               x (float): bla x
               y (int): bla y
           '''
           pass

In some cases, having to document all parameters is a nuisance, for
instance if many of your functions or methods just follow a **common
interface**. To remove this burden, the checker accepts missing
parameter documentation if one of the following phrases is found in
the docstring:

* For the other parameters, see

* For the parameters, see

(with arbitrary whitespace between the words). Please add a link to
the docstring defining the interface, e.g. a superclass method, after
"see":

   def callback(x, y, z):
       '''Sphinx style docstring for callback ...

       :param x: bla x
       :type x: int

       For the other parameters, see
       :class:`MyFrameworkUsingAndDefiningCallback`
       '''
       return x + y + z

   def callback(x, y, z):
       '''Google style docstring for callback ...

       Args:
           x (int): bla x

       For the other parameters, see
       :class:`MyFrameworkUsingAndDefiningCallback`
       '''
       return x + y + z

Naming inconsistencies in existing parameter and their type
documentations are still detected.


Parameter Documentation checker Options
---------------------------------------

accept-no-param-doc:
   Whether to accept totally missing parameter documentation in the
   docstring of a function that has parameters.

   Default: "yes"

accept-no-raise-doc:
   Whether to accept totally missing raises documentation in the
   docstring of a function that raises an exception.

   Default: "yes"

accept-no-return-doc:
   Whether to accept totally missing return documentation in the
   docstring of a function that returns a statement.

   Default: "yes"

accept-no-yields-doc:
   Whether to accept totally missing yields documentation in the
   docstring of a generator.

   Default: "yes"

default-docstring-type:
   If the docstring type cannot be guessed the specified docstring
   type will be used.

   Default: "default"


Parameter Documentation checker Messages
----------------------------------------

differing-param-doc (W9017):
   *"%s" differing in parameter documentation* Please check parameter
   names in declarations.

differing-type-doc (W9018):
   *"%s" differing in parameter type documentation* Please check
   parameter names in type declarations.

multiple-constructor-doc (W9005):
   *"%s" has constructor parameters documented in class and __init__*
   Please remove parameter declarations in the class or constructor.

missing-param-doc (W9015):
   *"%s" missing in parameter documentation* Please add parameter
   declarations for all parameters.

missing-type-doc (W9016):
   *"%s" missing in parameter type documentation* Please add parameter
   type declarations for all parameters.

missing-raises-doc (W9006):
   *"%s" not documented as being raised* Please document exceptions
   for all raised exception types.

useless-param-doc (W9019):
   *"%s" useless ignored parameter documentation* Please remove the
   ignored parameter documentation.

useless-type-doc (W9020):
   *"%s" useless ignored parameter type documentation* Please remove
   the ignored parameter type documentation.

missing-any-param-doc (W9021):
   *Missing any documentation in "%s"* Please add parameter and/or
   type documentation.

missing-return-doc (W9011):
   *Missing return documentation* Please add documentation about what
   this method returns.

missing-return-type-doc (W9012):
   *Missing return type documentation* Please document the type
   returned by this method.

missing-yield-doc (W9013):
   *Missing yield documentation* Please add documentation about what
   this generator yields.

missing-yield-type-doc (W9014):
   *Missing yield type documentation* Please document the type yielded
   by this method.

redundant-returns-doc (W9008):
   *Redundant returns documentation* Please remove the return/rtype
   documentation from this method.

redundant-yields-doc (W9010):
   *Redundant yields documentation* Please remove the yields
   documentation from this method.


Refactoring checker
===================

This checker is provided by "pylint.extensions.empty_comment".
Verbatim name of the checker is "refactoring".


Refactoring checker Messages
----------------------------

empty-comment (R2044):
   *Line with empty comment* Used when a # symbol appears on a line
   not followed by an actual comment


Set Membership checker
======================

This checker is provided by "pylint.extensions.set_membership".
Verbatim name of the checker is "set_membership".


Set Membership checker Messages
-------------------------------

use-set-for-membership (R6201):
   *Consider using set for membership test* Membership tests are more
   efficient when performed on a lookup optimized datatype like
   "sets".


Typing checker
==============

This checker is provided by "pylint.extensions.typing". Verbatim name
of the checker is "typing".


Typing checker Documentation
----------------------------

Find issue specifically related to type annotations.


Typing checker Options
----------------------

runtime-typing:
   Set to "no" if the app / library does **NOT** need to support
   runtime introspection of type annotations. If you use type
   annotations **exclusively** for type checking of an application,
   you're probably fine. For libraries, evaluate if some users what to
   access the type hints at runtime first, e.g., through
   "typing.get_type_hints". Applies to Python versions 3.7 - 3.9

   Default: "yes"


Typing checker Messages
-----------------------

deprecated-typing-alias (W6001):
   *'%s' is deprecated, use '%s' instead* Emitted when a deprecated
   typing alias is used.

consider-using-alias (R6002):
   *'%s' will be deprecated with PY39, consider using '%s' instead%s*
   Only emitted if 'runtime-typing=no' and a deprecated typing alias
   is used in a type annotation context in Python 3.7 or 3.8.

consider-alternative-union-syntax (R6003):
   *Consider using alternative Union syntax instead of '%s'%s* Emitted
   when 'typing.Union' or 'typing.Optional' is used instead of the
   alternative Union syntax 'int | None'.


While Used checker
==================

This checker is provided by "pylint.extensions.while_used". Verbatim
name of the checker is "while_used".


While Used checker Messages
---------------------------

while-used (W0149):
   *Used `while` loop* Unbounded *while* loops can often be rewritten
   as bounded *for* loops.
