rspec/rules/S5654/python/rule.adoc

== Why is this an issue?

As soon as the ``++yield++`` keyword is used the enclosing method or function becomes a generator. Thus ``++yield++`` should never be used in a function or method which is not intended to be a generator.


This rule raises an issue when ``++yield++`` or ``++yield from++`` are used in a function or method which is not a generator because:

* the function/method's return type annotation is not [``++typing.Generator[...]++``|https://docs.python.org/3/library/typing.html#typing.Generator]
* it is a special method which can never be a generator (ex: ``++__init__++``).


=== Noncompliant code example

[source,python]
----
class A:
    def __init__(self, value):
        self.value = value
        yield value  # Noncompliant

def mylist2() -> List[str]:
    yield ['string']  # Noncompliant. Return should be used instead of yield

def generator_ok() -> Generator[int, float, str]:
    sent = yield 42
    return '42'
----


=== Compliant solution

[source,python]
----
class A:
    def __init__(self, value):
        self.value = value

def mylist2() -> List[str]:
    return ['string']

def generator_ok() -> Generator[int, float, str]:
    sent = yield 42
    return '42'
----


== Resources

* https://docs.python.org/3/library/typing.html[Python documentation - Support for type hints]
* https://docs.python.org/3/reference/datamodel.html#special-method-names[Python documentation - Special method names]


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

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

=== Message

* Remove this "yield" statement
* Replace this "yield" keyword with "return" or change the return type annotation.


=== Highlighting

Primary: the "yield" keyword

Secondary: function/method's return type annotation if there is one


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

=== is related to: S2734

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