When working with nested blocks in Ansible, proper YAML indentation and syntax for conditional statements is crucial. The error occurs because the when clause isn't properly aligned with the nested block structure.

Here's the corrected version of your playbook with proper nesting:

- block:
    - postgresql_db: name={{ dbname }} state=absent
    - postgresql_db: name={{ dbname }}
    ...
    - block:
        - get_url: url={{ remote_database_dump }} dest={{ local_database_dump }}
        - command: pg_restore -d {{ dbname }} {{ local_database_dump }}
      when: remote_database_dump != ""
  become: true
  become_user: postgres
  become_method: su
  when: db_recreate == "true"

The key points to remember when nesting conditional blocks:

1. The inner 'when' clause must be indented exactly under the nested 'block'
2. Colon (:) is required after 'when'
3. The conditional expression needs proper spacing

Here's a more complex example showing multiple levels of nested conditionals:

- block:
    - debug: msg="Outer block execution"
    - block:
        - debug: msg="First nested block"
        - block:
            - debug: msg="Second nested level"
          when: second_level_condition
      when: first_level_condition
  when: outer_condition

Instead of deep nesting, consider these cleaner alternatives:

# Option 1: Separate tasks with individual when clauses
- postgresql_db: name={{ dbname }} state=absent
  when: db_recreate == "true"
  become: true
  become_user: postgres
  become_method: su

# Option 2: Use include_tasks with conditionals
- include_tasks: setup_db.yml
  when: db_recreate == "true"

When troubleshooting nested conditionals:

1. Use ansible-playbook --syntax-check
2. Start with minimal nesting and build up
3. Test conditions separately before combining
4. Use debug messages to verify execution paths

When working with Ansible playbooks, you might encounter situations where you need to nest conditional blocks. The typical error occurs when trying to apply a when clause to an inner block:

- block:
  - postgresql_db: name={{ dbname }} state=absent
  - postgresql_db: name={{ dbname }}
  ...
  - block:
     - get_url: url={{ remote_database_dump }} dest={{ local_database_dump }}
     - command: pg_restore -d {{ dbname }} {{ local_database_dump }}
    when remote_database_dump != ""
  become: true
  become_user: postgres
  become_method: su
  when: db_recreate == "true"

The error occurs because YAML requires proper indentation for nested structures. The when clause must be aligned with the block keyword it applies to:

- block:
    - postgresql_db: name={{ dbname }} state=absent
    - postgresql_db: name={{ dbname }}
    - block:
        - get_url: url={{ remote_database_dump }} dest={{ local_database_dump }}
        - command: pg_restore -d {{ dbname }} {{ local_database_dump }}
      when: remote_database_dump != ""
  become: true
  become_user: postgres
  become_method: su
  when: db_recreate == "true"

If you find nested blocks difficult to read, consider these alternatives:

Option 1: Apply conditions to individual tasks

- name: Remove existing database
  postgresql_db:
    name: "{{ dbname }}"
    state: absent
  when: db_recreate == "true"
  become: true
  become_user: postgres
  become_method: su

- name: Create new database
  postgresql_db:
    name: "{{ dbname }}"
  when: db_recreate == "true"
  become: true
  become_user: postgres
  become_method: su

- name: Download remote dump
  get_url:
    url: "{{ remote_database_dump }}"
    dest: "{{ local_database_dump }}"
  when: db_recreate == "true" and remote_database_dump != ""
  become: true
  become_user: postgres
  become_method: su

Option 2: Use include_tasks for complex conditional logic

- name: Handle database recreation
  block:
    - include_tasks: remove_and_create_db.yml
    - include_tasks: restore_from_dump.yml
      when: remote_database_dump != ""
  when: db_recreate == "true"
  become: true
  become_user: postgres
  become_method: su

• Always maintain consistent indentation (2 or 4 spaces)
• Consider breaking complex nested blocks into separate files
• Use comments to explain why conditions are needed
• Test playbooks with --syntax-check flag
• Keep the maximum nesting level to 2-3 for readability