support gather_facts: false; support setup-snapshot.yml (#53)

Some users use `gather_facts: false` in their playbooks.  This changes
the role to work in that case, by gathering only the facts it requires
to run.
CI testing can be sped up by creating a snapshot image pre-installed
with packages.  tests/setup-snapshot.yml can be used by a CI system
to do this.

tasks/main.yml

@@ -4,18 +4,7 @@
 
 # yamllint disable rule:line-length
 - name: Set version specific variables
-  include_vars: "{{ lookup('first_found', ffparams) }}"
-  vars:
-    ffparams:
-      files:
-        - "{{ ansible_facts['distribution'] }}_{{ ansible_facts['distribution_version'] }}.yml"
-        - "{{ ansible_facts['distribution'] }}_{{ ansible_facts['distribution_major_version'] }}.yml"  # yamllint disable-line rule:line-length
-        - "{{ ansible_facts['distribution'] }}.yml"
-        - "{{ ansible_facts['os_family'] }}.yml"
-        - "default.yml"
-      paths:
-        - "{{ role_path }}/vars"
-# yamllint enable rule:line-length
+  include_tasks: set_vars.yml
 
 - name: Include the appropriate provider tasks
   include_tasks: "main-{{ nbde_server_provider }}.yml"

tasks/set_vars.yml

@@ -0,0 +1,20 @@
+---
+- name: Ensure ansible_facts used by role
+  setup:
+    gather_subset: min
+  when: not ansible_facts.keys() | list |
+    intersect(__nbde_server_required_facts) ==
+    __nbde_server_required_facts
+
+- name: Set platform/version specific variables
+  include_vars: "{{ lookup('first_found', ffparams) }}"
+  vars:
+    ffparams:
+      files:
+        - "{{ ansible_facts['distribution'] }}_{{ ansible_facts['distribution_version'] }}.yml"  # yamllint disable-line rule:line-length
+        - "{{ ansible_facts['distribution'] }}_{{ ansible_facts['distribution_major_version'] }}.yml"  # yamllint disable-line rule:line-length
+        - "{{ ansible_facts['distribution'] }}.yml"
+        - "{{ ansible_facts['os_family'] }}.yml"
+        - "default.yml"
+      paths:
+        - "{{ role_path }}/vars"

tests/setup-snapshot.yml

@@ -0,0 +1,12 @@
+- hosts: all
+  tasks:
+    - name: Set platform/version specific variables
+      include_role:
+        name: linux-system-roles.nbde_server
+        tasks_from: set_vars.yml
+        public: true
+
+    - name: Install test packages
+      package:
+        name: "{{ __nbde_server_packages }}"
+        state: present

tests/tests_default.yml

@@ -1,7 +1,7 @@
 ---
 - name: Ensure that the role runs with default parameters
   hosts: all
-
+  gather_facts: false
   roles:
     - linux-system-roles.nbde_server
 

vars/main.yml

@@ -1,4 +1,11 @@
 # SPDX-License-Identifier: MIT
 ---
 
+# ansible_facts required by the role
+__nbde_server_required_facts:
+  - distribution
+  - distribution_major_version
+  - distribution_version
+  - os_family
+
 # vim:set ts=2 sw=2 et: