rspec/rules/S5655/python/rule.adoc

== Why is this an issue?

The CPython interpreter does not check arguments type when functions are called. However a function can express the type it expects for each argument in its documentation or by using https://www.python.org/dev/peps/pep-0484/[Type Hints]. Calling such a function with an argument of a different type can easily create a bug. Even if it works right now it can fail later when APIs evolve or when type checks are added (ex: with ``++isinstance++``).


This rule raises an issue when a function or method is called with an argument of a different type than the one described in its type annotations. It also checks argument types for builtin functions.


=== Noncompliant code example

[source,python]
----
def func(var: str):
    pass

func(42)  # Noncompliant

len(1)  # Noncompliant
----


=== Compliant solution

[source,python]
----
def func(var: str):
    pass

func("42")

len("1")
----


== Resources

* https://docs.python.org/3/library/functions.html#built-in-funcs[Python documentation - builtins]
* https://www.python.org/dev/peps/pep-0484/[PEP 484 — Type Hints]
* https://docs.python.org/3/library/typing.html[Python documentation - typing — Support for type hints]

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

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

=== Message

* Change this argument of type XXX; Function FFF expects type YYY


=== Highlighting

Primary: the expression provided as argument

Secondary:

* location: definition of the function called
* message: "Function definition"


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