Lineinfile race with connection: local

lineinfile-race-bug.yml

---
- name: Sanity check
  hosts: all
  connection: local
  tasks:
    - fail: msg="You need at least two hosts to run this play against, but more is better"
      when: play_hosts|length < 2
      run_once: yes

- name: Generate two tempfiles with run_once, and make a list
  hosts: all
  connection: local
  tasks:
    - shell: mktemp
      register: parallel
      run_once: true
    - shell: mktemp
      register: serial
      run_once: true

- name: Write the hostname to our parallel tempfile 
  hosts: all
  connection: local
  tasks:
    - lineinfile: dest={{ parallel.stdout }} line="{{ inventory_hostname }} at {{ ansible_date_time.date }} {{ ansible_date_time.time }} {{ ansible_date_time.tz }}" create=no state=present


- name: Write the hostname to our serial tempfile 
  hosts: all
  connection: local
  serial: 1
  tasks:
    - lineinfile: dest={{ serial.stdout }} line="{{ inventory_hostname }} at {{ ansible_date_time.date }} {{ ansible_date_time.time }} {{ ansible_date_time.tz }}" create=no state=present


- name: Cat both tempfiles and print them
  hosts: all
  connection: local
  tasks:
    - shell: cat {{ parallel.stdout }}
      register: paralleldata
      run_once: yes
    - shell: cat {{ serial.stdout }}
      register: serialdata
      run_once: yes
    - debug: var=paralleldata.stdout_lines
      run_once: yes
    - debug: var=serialdata.stdout_lines
      run_once: yes
    - debug: msg="Serial play has {{ serialdata.stdout_lines|length }} lines, parallel play has {{ paralleldata.stdout_lines|length }} lines"
      run_once: yes
    - fail: msg="Unexpected behaviour from lineinfiles module with connection local"
      when: "serialdata.stdout_lines|length  != paralleldata.stdout_lines|length"
      run_once: yes