Add trim_blocks=False argument to template lookup plugin

[mdavis-xyz]

Summary

The template module has an option for trim_blocks=False. I would like to have the same option with the template lookup plugin.

An alternative solution would be to make trim_blocks in the template module recursively apply to any template lookups inside that template.

My use case is that I'm generating AWS CloudFormation yaml templates with Jinja. Since some CloudFormation templates require nested json or yaml as an escaped literal string inside the overall yaml, I have recursive templates. For the top-level template I use the template module with trim_blocks=False. And inside that template I use stuff like {{ lookup('template', x) | from_yaml | to_json }} plugin to evaluate other templates, then convert them to json to embed as a string inside my overall yaml template. This fails currently because the default (and only) behavior of lookup('template', x) is to trim blocks. When my jinja template is of something where indentation matters (e.g. yaml), this messes with the indentation in a way that changes the meaning of the file entirely, typically resulting in something that is broken and undeployable. This might sound like an obscure use case, but really this applies to any use of the template plugin to render a template where leading whitespace matters (e.g. yaml, python, markdown)

Issue Type

Feature Idea

Component Name

lib/ansible/plugins/lookup/template.py

Additional Information

test.j2 (note the leading spaces)

  First Line
  {# comment #}
  Second Line
  {#-comment #}
  third line

playbook:

---
- hosts: localhost
  connection: local
  vars:
    path: 'test.j2'
    module_output: 'module-output.txt'
    plugin_output: 'plugin-output.txt'
  tasks:
    - name: use template module
      template:
        src: "{{ path }}"
        dest: "{{ module_output }}"
        trim_blocks: False

    - name: lookup plugin
      copy:
        content: "{{ lookup('template', path, trim_blocks=False) }}"
        dest: "{{ plugin_output }}"
        
    - name: compare
      assert:
        that:
        - lookup('file', plugin_output) == lookup('file', module_output)

Desired behavior: assertion passes

Current behavior: assertion fails. trim_blocks in lookup is ignored.

Code of Conduct

• I agree to follow the Ansible Code of Conduct

[ansibot]

Files identified in the description:

• lib/ansible/plugins/lookup/template.py

If these files are incorrect, please update the component name section of the description or use the !component bot command.

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[mdavis-xyz]

I'm struggling to find the right part of the codebase for this change.

I think this is the relevant part of the template module, and this is the relevant part of the plugin module. So I just need to add another argument to that second link?

[sivel]

lib/ansible/plugins/lookup/template.py is where it needs to go