Ansible blockinfile replace everything except a block

Question

I am trying to replace everything except a special block using Ansible blockinfile. It would be safe to assume that this special block to be at the beginning of the file.

File content before ansible run:

# BEGIN SPECIAL
blah
# END OF SPECIAL
... bunch of configs

Expected file content after ansible run:

# BEGIN SPECIAL
blah
# END OF SPECIAL
[MY REPLACED CONFIGS]

There are two problems with using blockinfile marker.

1. marker_start and marker_end do not support regex
2. Cannot specify EOF as marker_end

My ansible task:

- name: testing replacing file
  blockinfile:
    path: /tmp/testfile
    marker: "{mark}"
    marker_begin: "# END OF SPECIAL" 
    marker_end: EOF
    block: "[MY REPLACED CONFIGS]"
    state: present

This does not seem to do the trick. Is there a way to achieve this with blockinfile?

Answer 1

Q: "Is there a way to achieve this with blockinfile?"

A: No. The module blockinfile can't change content outside the block. Instead, a simple template would do the job. For example, given the variables

    begin: "# BEGIN SPECIAL"
    end: "# END OF SPECIAL"
    block2: "[MY REPLACED CONFIGS]"

Read the block

    - command: "sed -n '/{{ begin }}/,/{{ end }}/p' tmp/testfile"
      register: result
    - set_fact:
        block1: "{{ result.stdout_lines[1:-1]|join('\n') }}"

gives

  block1: blah

Now, put all elements together

    - copy:
        dest: tmp/testfile
        content: |
          {{ begin }}
          {{ block1 }}
          {{ end }}
          {{ block2 }}

gives

shell> cat tmp/testfile
# BEGIN SPECIAL
blah
# END OF SPECIAL
[MY REPLACED CONFIGS]