This rule raises an issue when a function is called with multiple values for the same parameter.

== Why is this an issue?

When a function is called, it accepts only one value per parameter. The Python interpreter will raise a `SyntaxError` when the same parameter is provided more than once, i.e. `myfunction(a=1, a=2)`.

Other less obvious cases will also fail at runtime by raising a `TypeError`, when: 

* An argument is provided by value and position at the same time.
* An argument is provided twice, once via unpacking and once by value or position.

=== Code examples 

==== Noncompliant code example

[source,python,diff-id=1,diff-type=noncompliant]
----
def func(a, b, c):
    return a * b * c

func(6, 93, 31, c=62) # Noncompliant: argument "c" is duplicated

params = {'c':31}
func(6, 93, 31, **params) # Noncompliant: argument "c" is duplicated
func(6, 93, c=62, **params) # Noncompliant: argument "c" is duplicated
----

==== Compliant solution

[source,python,diff-id=1,diff-type=compliant]
----
def func(a, b, c):
    return a * b * c

func(c=31, b=93, a=6) # Compliant  

params = {'c':31}
func(6, 93, **params) # Compliant
----


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

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

=== Message

{xxx} argument is duplicated in {function} call


=== Highlighting

Primary: the first appearance of duplicated argument

Secondary:

* location: the others argument duplicated
** message: argument also passed here

* location: the signature of the called function
* message: function definition


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

=== on 23 Apr 2020, 17:28:22 Nicolas Harraudeau wrote:
The following use case was removed because it is a syntax error and we don't want to target those:

----
func(c=31, b=93, c=62)
----

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