link task depending on content - regex

Question

I have 3 tasks..
first task checks if a file contains <ip> <hostname> pattern
second task adds a line if the sought after string is not present.
third task corrects the line if it is bad.
the 3 tasks run well independently but I want to run them together somehow linked.
I have the following playbook using as model /etc/hosts.
---
- name: check hosts playbook
hosts: centos
tasks:
- name: check whether a line in the form of '<ip> <hostname>' exists
lineinfile:
path: /var/tmp/hosts
regexp: '^\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}\s\w+'
state: absent
check_mode: true
register: line_exists
- name: append_host_file
lineinfile:
path: /var/tmp/hosts
insertafter: '^(127\.0\.0\.1|)(?:\d{1,3}\.){3}\d{1,3}'
line: '{{ ansible_default_ipv4.address }} {{ansible_hostname }}'
backup: yes
when: not line_exists.changed
- name: correct_hosts_file
lineinfile:
path: /var/tmp/hosts
regexp: '^(?!{{ ansible_default_ipv4.address }}\s{{ ansible_hostname }})(?:\d{1,3}\.){3}\d{1,3}\s\w+'
line: '{{ ansible_default_ipv4.address }} {{ansible_hostname }}'
when: line_exists.changed
the issue i have is the correct task is running when the line is correct.. so i need to use some other sort of criteria to prevent it from running when the line in the file is correct...if the line in the file is wrong it work because it replaces it.

Answer 1

It's a common problem with lineinfile, it's not that useful as it looks.
My advice: load file content into variable (- command: cat /etc/hosts), register it (register: old_hosts) than iterate over each line of that variable in a template.
- name: get hosts
command: cat /etc/hosts
register: old_hosts
- name: write hosts
template:
src: hosts.j2
dest: /etc/hosts
hosts.j2:
{% for line in old_hosts.stdout_lines %}
{% if line (....) %}
...
{% endif %}
{% endfor %}