Ansible file lookups when file is potentially not present

lookup-test.yml

---
# example playbook for file lookup when file may be missing
# file lookup plugin throws an exception for a missing file that can't be caught
# so check file(s) exist first and only perform lookups on those that do

- hosts: all
  become: false
  vars:
    filelist:
      - thisfile
      - thatfile
  tasks:
  # OPTION 1:
  # check for each file individually
  - name: check files exist
    stat:
      path: "{{ item }}"
      get_checksum: no  # & disable MD5 etc to save time
    with_items: "{{ filelist }}"
    register: validfiles
  
  # registered variables from loops have a complex structure, check the result here:
  - debug:
      var: validfiles
      verbosity: 1
  
  # OPTION 2:
  # alternatively, get a list of all the files (with optional excludes)
  - name: get list of all files
    local_action:
      module: find
      paths: "path/to/files"  # e.g. "{{ (playbook_dir + '/blah/dir') }}"
      excludes: '*~'
    register: allfiles

  - name: output file contents
    debug:
      msg: "File contents are: {{ lookup('file', item.item) }}"
    with_items: "{{ validfiles.results }}"  # for OPTION 2, use "{{ allfiles }}" from above instead and remove conditional check
    #with_items: "{{ files_wanted | intersect(allfiles) }}" # OR filter against a predefined list of relevant files
    when: item.stat.exists  # OPTION 1 only

Ok, this is why Ansible sucks at some points, and this is a perfect examples, 3 tasks to do only a basic thing. Not you're fault, but Ansible can drive crazy for such little things.

It's actually two tasks, only one of the first two is required; I've edited to try to make this clearer. As it turns out, Ansible 2.6 adds an "error='ignore'" option to the lookup plugins so all this may be redundant. However, filtering the list of files against a predefined list of interest with intersect() can be useful, e.g. for reading SSH public key files for a set of users that have them.