Ansible: include_role on a loop running unexpected number of times - ansible

Question

I am trying to use include_role with items
---
- hosts: cluster
tasks:
- block:
- name: Execute test role
include_role:
name: testrole
with_items:
- 'one'
...
My role is
---
- name: Just debugging
debug:
...
The issue is that it seems that the role is being ran by each host X times per item where X is the number of hosts.
PLAY [cluster] *****************************************************************
TASK [setup] *******************************************************************
ok: [thisNode]
ok: [dww]
TASK [Execute test role] *******************************************************
TASK [testrole : Just debugging] ***********************************************
ok: [thisNode] => {
"msg": "Hello world!"
}
ok: [dww] => {
"msg": "Hello world!"
}
TASK [testrole : Just debugging] ***********************************************
ok: [thisNode] => {
"msg": "Hello world!"
}
ok: [dww] => {
"msg": "Hello world!"
}
PLAY RECAP *********************************************************************
dww : ok=3 changed=0 unreachable=0 failed=0
thisNode : ok=3 changed=0 unreachable=0 failed=0
Why is this happening and how can I fix it?
Ansible hosts:
[cluster]
thisNode ansible_host=localhost ansible_connection=local
dww
I cannot delegate the task because, in the real role, the task must be executed in each of the hosts.
Using allow_duplicates: no still outputs the same.
---
- hosts: cluster
tasks:
- name: Execute test role
include_role:
name: testrole
allow_duplicates: False
with_items:
- 'one'
...

Answer 1

As a workaround you can add allow_duplicates: false to prevent Ansible from running the same role twice with the same parameters.
Clearly the module is looped twice: once with hosts, the other time with the specified items. As it is supposed to runs the action against all hosts, the outer loop gets executed twice.
It's a new module in preview state and this behaviour should probably be files as an issue.
Ansible has an internal parameter BYPASS_HOST_LOOP to avoid such situations and this mechanism should probably be used by this module.

Answer 2

I had the same problem and allow_duplicates: False did not change anything.
It seems that setting serial: 1 on the play and it somehow solved it. This is a workaround that probably will work for a small number of hosts.