Failed and expression in ansible when clause

test.yml

# Configure yum repos based on requirement for stable,
# unstable, current, or specific assembly number
---
- hosts: test

  vars:
    branch: trunk
    branch_repo: unstable
  
  tasks:
    - name: use unstable repository
      action: command echo -u
      register: repo_flag
      when: branch_repo == 'unstable'

    - name: use stable repository
      action: command echo -s
      register: repo_flag
      when: branch_repo == 'stable'

    - name: use current repository
      action: command echo -s
      register: repo_flag
      when: branch_repo == 'current'

    - name: use latest repository
      action: command echo -s
      register: repo_flag
      when: branch_repo == 'latest'

    - name: use assembly number
      action: command echo -a {{ branch_repo['assembly'] }}
      register: repo_flag
      when: mapping(branch_repo) and defined(branch_repo['assembly'])

    - name: show repo configuration
      action: command echo {{ branch }} {{ branch_repo }} {{ repo_flag }}