Can't figure out why subnet is being updated

Question

I am creating a VPC in AWS using Ansible. The following play is run

- name: create vpc with multi-az subnets
  ec2_vpc:
    region: "{{ region }}"
    cidr_block: "{{ vpc_cidr_block }}"
    resource_tags: '{"Name":"{{ prefix }}_vpc"}'
    subnets:
      - cidr: "{{ vpc_cidr_subnet_public_0 }}"
        az: "{{ region }}{{ availability_zone_0 }}"
        resource_tags: '{"Name":"{{ prefix }}_subnet_public_0", "Class":"web", "Partner":prefix }'
      - cidr: "{{ vpc_cidr_subnet_private_0 }}"
        az: "{{ region }}{{ availability_zone_0 }}"
        resource_tags: '{"Name":"{{ prefix }}_subnet_private_0", "Class":"db", "Partner":prefix }'
      - cidr: "{{ vpc_cidr_subnet_private_1 }}"
        az: "{{ region }}{{ availability_zone_1 }}"
        resource_tags: '{"Name":"{{ prefix }}_subnet_private_1", "Class":"db", "Partner":prefix }'
    internet_gateway: yes
    route_tables:
      - subnets:
        - "{{ vpc_cidr_subnet_public_0 }}"
        routes:
          - dest: 0.0.0.0/0
            gw: igw
    wait: yes
  register: vpc

First time around this creates everything perfectly. Second time around, I expect it to not do anything as everything has been created, however, the public subnet is updated to a private one.

Why? What am I doing wrong?

[UPDATE]

Here are the variables:

---
region: eu-west-1
prefix: staging
vpc_environment: staging
vpc_cidr_block: 20.0.0.0/16
vpc_cidr_subnet_public_0: 20.0.0.0/24
vpc_cidr_subnet_private_0: 20.0.1.0/24
vpc_cidr_subnet_private_1: 20.0.2.0/24
availability_zone_0: b
availability_zone_1: c

Also just to clarify on what change is happening. All the resource tags of the one subnet (public) are being overwritten with the tags of another subnet (private).

Answer 1

This was caused by a bug in ansible-modules-core in master - ec2_vpc. I have logged a bug and created a PR to resolve the issue. See PR for details and the actual break. Hopefully it gets merged soon!

[UPDATE] Merged