Ansible become_user not picking up path correctly

Question

Here's the code showing what I believe is a problem:

# Debugging path problems with sudo
---
- hosts: webservers
  remote_user: root
  tasks:
  - name: echo path
    command: echo $PATH
    register: output
    changed_when: False

  - name: display root path output
    debug: "msg={{ output.stdout }}"

  # Now try as apache
  - name: echo path
    command: echo $PATH
    become: true
    become_user: apache
    become_method: sudo
    register: output
    changed_when: False

  - name: display wrong output
    debug: "msg={{ output.stdout }}"

  # This is the fix
  - name: echo path
    command: echo $PATH
    environment:
      PATH: "{{ ansible_env.PATH }}"
    become: true
    become_user: apache
    become_method: sudo
    register: output
    changed_when: False

  - name: display fixed output
    debug: "msg={{ output.stdout }}"

Here's the output, you can see that the path is not complete without adding "the fix".

TASK [echo path] ***************************************************************
ok: [webapp]

TASK [display root path output] ************************************************
ok: [webapp] => {
    "changed": false, 
    "msg": "/usr/lib64/qt-3.3/bin:/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin"
}

TASK [echo path] ***************************************************************
ok: [webapp]

TASK [display wrong output] ****************************************************
ok: [webapp] => {
    "changed": false, 
    "msg": "/sbin:/bin:/usr/sbin:/usr/bin"
}

TASK [echo path] ***************************************************************
ok: [webapp]

TASK [display fixed output] ****************************************************
ok: [webapp] => {
    "changed": false, 
    "msg": "/usr/lib64/qt-3.3/bin:/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin"
}

Why is this fix necessary, is this a bug?

This is on CentOS 6.7 and using Ansible 2.0

Solution

This is normal and expected behavior.

Remember that sudo sanitizes the environment when switching users, which is why you end up with a minimal default PATH.

The remainder of the items in the PATH come from shell startup scripts, which are not being run when you (or rather Ansible) call sudo <command>, because it is not asking for an interactive or login shell.

If you have to run a command which isn't in a default location, supply its path explicitly.