This rule raises an issue when a comparison to `None` is invariant.

== Why is this an issue?

Checking if a variable or parameter is `None` should only be done when you expect that it can be `None`. Doing so when the variable is always `None` or never `None` is confusing at best. At worse, there is a bug and the variable is not updated properly.

This rule raises an issue when expressions `X is None`, `X is not None`, `X == None` or `X != None` are constant, i.e. `X` is always None or never None.

=== Code examples

==== Noncompliant code example

[source,python,diff-id=1,diff-type=noncompliant]
----
def foo():
    my_var = None
    if my_var == None:  # Noncompliant: always True.
        ...
----

==== Compliant solution

[source,python,diff-id=1,diff-type=compliant]
----
def foo(my_var):
    if my_var == None:
        ...
----


:link-with-uscores1: https://docs.python.org/3/reference/datamodel.html#object.__eq__

== Resources

=== Documentation

* Python documentation - https://docs.python.org/3/reference/expressions.html#is-not[Identity comparisons]
* Python documentation - {link-with-uscores1}[``++__eq__++`` operator]



ifdef::env-github,rspecator-view[]

'''
== Implementation Specification
(visible only on this page)

=== Message

* Remove this identity check; it will always be True/False
* Remove this == comparison; it will always be True/False
* Remove this != comparison; it will always be True/False


=== Highlighting

the "is", "is not", "==" or "!=" operator


'''
== Comments And Links
(visible only on this page)

=== is related to: S5914

endif::env-github,rspecator-view[]
