version_test_gotchas.yml

#!/usr/bin/env ansible-playbook
---
- name: Test behaviour of version test
  hosts: localhost
  gather_facts: false
  tasks:
    - name: Expected results, comparing a.b.c <-> x.y.z, or a.b <-> x.y
      debug:
        msg:
          - '"1.0" is version("1.0", "==")      -> {{ "1.0" is version("1.0", "==") }}'
          - '"1.0.0" is version("1.0.0", "==")  -> {{ "1.0.0" is version("1.0.0", "==") }}'
          - '"2.0" is version("1.0", ">")       -> {{ "2.0" is version("1.0", ">") }}'
          - '"2.0.0" is version("1.0.0", ">")   -> {{ "2.0.0" is version("1.0.0", ">") }}'

    - name: Gotchas, comparing a.b.c <-> x.y, or a.b <-> x.y.z
      debug:
        msg:
          - '"1.0.0" is version("1.0", "==")    -> {{ "1.0.0" is version("1.0", "==") }}'
          - '"1.0" is version("1.0.0", "==")    -> {{ "1.0" is version("1.0.0", "==") }}'
          - '"1.0.0" is version("1.0", ">")     -> {{ "1.0.0" is version("1.0", ">") }}'
          - '"3.0.0" is version("3.0.0b1", ">") -> {{ "3.0.0" is version("3.0.0b1", ">") }}'

PLAY [Test behaviour of version test] *****************************************************************************

TASK [Expected results, comparing a.b.c <-> x.y.z, or a.b <-> x.y] ************************************************
ok: [localhost] => 
  msg:
  - '"1.0" is version("1.0", "==")      -> True'
  - '"1.0.0" is version("1.0.0", "==")  -> True'
  - '"2.0" is version("1.0", ">")       -> True'
  - '"2.0.0" is version("1.0.0", ">")   -> True'

TASK [Gotchas, comparing a.b.c <-> x.y, or a.b <-> x.y.z] *********************************************************
ok: [localhost] => 
  msg:
  - '"1.0.0" is version("1.0", "==")    -> False'
  - '"1.0" is version("1.0.0", "==")    -> False'
  - '"1.0.0" is version("1.0", ">")     -> True'
  - '"3.0.0" is version("3.0.0b1", ">") -> False'

PLAY RECAP ********************************************************************************************************
localhost                  : ok=2    changed=0    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0 

See also https://twitter.com/moreati/status/1357074302848430080

Paint me 0.0.1 & call me pre-release. Ansible's version test has a strict mode that does the right thing
Do: '1.2.0' is version('1.2', '==', strict=True) # true
Do: '1.2.0' is version('1.2', '>', strict=True) # false
Do: '1.2.0' is version('1.2.0a1', '>', strict=True) # true