rspec/rules/S5724/python/rule.adoc

== Why is this an issue?

Property getter, setter and deleter methods are called by the python interpreter with a specific number or arguments:

* only "self" for property getter and deleter methods.
* "self" and a value for setter methods.

Adding any other parameter, or removing these mandatory parameters will make method calls fail.


This rule raises an issue when:

* too many parameters are defined in a property getter, setter or deleter method.
* the value parameter is missing in a property setter method.


=== Noncompliant code example

[source,python]
----
class A:
    @property
    def foo(self, unexpected, unexpected2):  # Noncompliant. Too many parameters.
        return self._foo

    @foo.setter
    def foo(self, value, unexpected):  # Noncompliant. Too many parameters.
        self._foo = value

    @foo.deleter
    def foo(self, unexpected):  # Noncompliant. Too many parameters.
        del self._foo

class B:
    def get_foo(self, unexpected):  # Noncompliant. Too many parameters.
        return self._foo

    def set_foo(self, value, unexpected):  # Noncompliant. Too many parameters.
        self._foo = value

    def del_foo(self, unexpected):  # Noncompliant. Too many parameters.
        del self._foo

    foo = property(get_foo, set_foo, del_foo, "'foo' property.")
----


=== Compliant solution

[source,python]
----
class A:
    @property
    def foo(self):
        return self._foo

    @foo.setter
    def foo(self, value):
        self._foo = value

    @foo.deleter
    def foo(self):
        del self._foo

class B:
    def get_foo(self):
        return self._foo

    def set_foo(self, value):
        self._foo = value

    def del_foo(self):
        del self._foo

    foo = property(get_foo, set_foo, del_foo, "'foo' property.")
----


== Resources

*  https://docs.python.org/3/library/functions.html#property[Python Documentation - Built-in Functions - property]


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