Incorrect Ansible Jinja2 template concatenation - Stack Overflow

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Considering the following test playbook:

---
- name: Playbook
  hosts: localhost
  become: false
  gather_facts: false
  vars:
    modes:
      - ReadWriteOnce
  tasks:
    - name: Template output
      ansible.builtin.debug:
        msg: "{{ lookup('ansible.builtin.template', 'template.j2') }}"

And related template.js Jinja2 template:

storage:
  accessModes:
    {{ modes | to_nice_yaml | indent(4) }}
  resources:
    requests:
      storage: 5Gi

The output is:

ok: [localhost] =>
  msg: |-
    storage:
      accessModes:
        - ReadWriteOnce

      resources:
        requests:
          storage: 50Gi

My goal is to remove the empty line present after ReadWriteOnce list element, while keeping the exact yaml structure presented above. I tried setting into template the newline suppression with -, after indent(4):

storage:
  accessModes:
    {{ modes | to_nice_yaml | indent(4) -}}
  resources:
    requests:
      storage: 5Gi

Unfortunately, this produces an unexpected yaml formatting, note the resources:

ok: [localhost] =>
  msg: |-
    storage:
      accessModes:
        - ReadWriteOnce
    resources: <-- resources are shifted to left, by two spaces
        requests:
          storage: 5Gi

I'm wondering what is the correct fix for this issue? Thank you for your suggestions.

Considering the following test playbook:

---
- name: Playbook
  hosts: localhost
  become: false
  gather_facts: false
  vars:
    modes:
      - ReadWriteOnce
  tasks:
    - name: Template output
      ansible.builtin.debug:
        msg: "{{ lookup('ansible.builtin.template', 'template.j2') }}"

And related template.js Jinja2 template:

storage:
  accessModes:
    {{ modes | to_nice_yaml | indent(4) }}
  resources:
    requests:
      storage: 5Gi

The output is:

ok: [localhost] =>
  msg: |-
    storage:
      accessModes:
        - ReadWriteOnce

      resources:
        requests:
          storage: 50Gi

My goal is to remove the empty line present after ReadWriteOnce list element, while keeping the exact yaml structure presented above. I tried setting into template the newline suppression with -, after indent(4):

storage:
  accessModes:
    {{ modes | to_nice_yaml | indent(4) -}}
  resources:
    requests:
      storage: 5Gi

Unfortunately, this produces an unexpected yaml formatting, note the resources:

ok: [localhost] =>
  msg: |-
    storage:
      accessModes:
        - ReadWriteOnce
    resources: <-- resources are shifted to left, by two spaces
        requests:
          storage: 5Gi

I'm wondering what is the correct fix for this issue? Thank you for your suggestions.

• ansible
• jinja2

• accessModes:{{ modes | to_yaml | replace('\n', '') | indent(4, False) }} – 0xn0b174 Commented yesterday
• I know the actual yaml is valid accessModes: [ReadWriteOnce, ReadWriteOncePod], but I want to respect the OP expected output. – Floren Commented yesterday

2 Answers 2

Use the template to create the structure only

shell> cat template.j2
storage:
  accessModes: {{ modes }}
  resources:
    requests:
      storage: 5Gi

The output of the template lookup plugin is a string. Convert it to YAML. For example,

result: "{{ lookup('template', 'template.j2') | from_yaml }}"

Then ask the filter to_nice_yaml to format the output

    - debug:
        msg: |
          {{ result | to_nice_yaml(indent=4) }}

gives

    msg: |-
        storage:
            accessModes:
            - ReadWriteOnce
            resources:
                requests:
                    storage: 5Gi

You'll have to ask the Ansible callback to write YAML. For example,

shell> ANSIBLE_CALLBACK_RESULT_FORMAT=yaml ansible-playbook pb.yml

Notes:

• The list isn't indented inside the dictionary. See python yaml.dump bad indentation.

• Run the play below to see the results of various options.

shell> cat pb.yml
- hosts: localhost
  gather_facts: false

  vars:

    modes: [ReadWriteOnce]

  tasks:

    - debug:
        msg: |
          {{ result | type_debug }}

          {{ result | to_nice_yaml(indent=4) }}

          {{ result | to_nice_yaml | indent(4, true) }}

          {{ result | to_nice_yaml(indent=4) | indent(4) }}
      vars:
        result: "{{ lookup('template', 'template.j2') | from_yaml }}"
#       result: "{{ lookup('template', 'template.j2') }}"

Thanks to @vladimir-botka's hint mentioning the template lookup plugin outputs a string, I figured an easy fix:

storage:
  accessModes:
    {{ modes | to_nice_yaml | trim | indent(4) }}
  resources:
    requests:
      storage: 5Gi

The trim takes care of the problematic code output:

ok: [localhost] =>
  msg: |-
    storage:
      accessModes:
        - ReadWriteOnce
      resources:
        requests:
          storage: 50Gi

Related to indent(4) usage, I'm using it to inject the contents of a template, into another template:

alertmanager:
  config:
    {{ lookup('ansible.builtin.template', 'config_alertmanager.j2') | trim | indent(4) }}

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