Unicode error while increment variable value - ansible

Question

When I work with static variables it works absolutely fine. But when I try to use dynamic it does not work.
The playbook:
---
- hosts: Swi1
vars:
NewOne: 0
provider:
host: "192.168.0.30"
transport: "cli"
username: "cisco"
password: "cisco"
tasks:
- name: gather facts
register: iosfacts
ios_facts:
provider: "{{ provider }}"
- name: Display the value of the counter
debug:
msg: "NewOne={{ NewOne }} / Data type={{ NewOne | type_debug }}"
- name: interface description
set_fact:
NewOne: " {{ NewOne + 1 }}"
parents: "interface {{ item.key }}"
with_dict: "{{ iosfacts.ansible_facts.ansible_net_interfaces }}"
when: item.value.operstatus == "up"
- debug:
msg: " This is Debug {{ NewOne }}"
Gives the error:
fatal: [Swi1]: FAILED! => {"msg": "Unexpected templating type error
occurred on ({{ NewOne + 1 }}): coercing to Unicode: need string or
buffer, int found"}

Answer 1

If you want to do an increment on a variable, you need to recast it as an int, as set_fact will always make you end up with a string.
As an example, the two tasks:
- set_fact:
NewOne: "{{ NewOne | d(0) + 1 }}"
- debug:
var: NewOne | type_debug
Are giving
TASK [set_fact] ***************************************************************
ok: [localhost]
TASK [debug] ******************************************************************
ok: [localhost] =>
NewOne | type_debug: str
The fix is, then, to use the int filter.
Given:
- set_fact:
NewOne: "{{ NewOne | d(0) | int + 1 }}"
loop: "{{ range(1, 4) }}"
- debug:
var: NewOne
This yields the expected
TASK [set_fact] ***************************************************************
ok: [localhost] => (item=1)
ok: [localhost] => (item=2)
ok: [localhost] => (item=3)
TASK [debug] ******************************************************************
ok: [localhost] =>
NewOne: '3'
But then with your use case, there are more elaborated and shorter way to achieve the same:
- set_fact:
NewOne: >-
{{
iosfacts
.ansible_facts
.ansible_net_interfaces
| selectattr('value.operstatus', '==', 'up')
| length
}}
Given:
- debug:
msg: >-
{{
iosfacts
.ansible_facts
.ansible_net_interfaces
| selectattr('value.operstatus', '==', 'up')
| length
}}
vars:
iosfacts:
ansible_facts:
ansible_net_interfaces:
- value:
operstatus: up
- value:
operstatus: down
- value:
operstatus: up
This yields:
ok: [localhost] =>
msg: '2'

Answer 2

It seems you are trying to implement a loop counter with a programming paradigm, which isn't plain possible in that way since Ansible is not a programming language but a Configuration Management Tool in which you declare a state.
Your current issue is reproducible in the following way:
---
- hosts: localhost
become: false
gather_facts: false
vars:
NewOne: 0
tasks:
- name: Show var
debug:
msg: "{{ NewOne | type_debug }}"
- name: Add value
set_fact:
NewOne: " {{ NewOne + 1 }}"
loop: [1, 2, 3]
- name: Show result
debug:
msg: "{{ NewOne }}
resulting into an output of
TASK [Add value] *************
ok: [localhost] => (item=1)
fatal: [localhost]: FAILED! =>
msg: 'Unexpected templating type error occurred on ( {{ NewOne + 1 }}): coercing to Unicode: need string or buffer, int found'
Possible Solutions
You may have a look into Migrating from with_X to loop and Extended loop variables as an iteration counter is already provided there.
An other approach is given via type casting with filter in the answer of #β.εηοιτ.βε.
There as well if you are just interested in the amount of occurrences of certain status, like interface status up or down.
Further Q&A
Ansible set_fact type cast
Further Documentation
Discovering the data type
Forcing the data type