How to pass variable into role

[liubo]

SUMMARY

It seems hard to send a param into a role. The rule of `vars` is confusing.

# What I want is overwrite `version` in role `b` by `version` in role `a`
# roles/a/default/main.yml
version: v1.0.1
# roles/a/tasks/main.yml
- name: include role
  include_role:
    name: b
  vars:
    version: "{{ version }}"


# roles/b/default/main.yml
version: ""
# roles/b/tasks/main.yml
- name: ouput version
  debug:
    var: version

EXPECTED RESULTS

I can pass the `version` variable into role `b` without any variable name changes of role b and a

ACTUAL RESULTS

1. I have to change `version` to `_version` in role `a`.

Some problems will happened if `_version` is also defined by `b`. And I have to know all inner variables of `b`

2. I have to undefine `version` in role `b`

Role b can't have any default value of `version`.

It seems hard to keep independent of role.

https://github.com/ansible/ansible/issues/41257

[Brian Coca]

'role defaults' are special, they do make them available for the rest
of the play but a role will always give priority to their own default
definition.



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Brian Coca