roles/php-fpm: Fix logic

First, we cannot do a global check for has_wordpress or needs_php,
as those are defined per nginx vhost. Second, I realized that this
was only working in the past because vhosts that had WordPress or
needed PHP were listed first in the nginx_vhosts dict.

This changes the logic to first check if any vhosts have WordPress
or need PHP, then sets a fact that we can use to decide whether to
run php-fpm tasks or not.

roles/php-fpm/tasks/Debian_10.yml

@@ -28,7 +28,8 @@
   - name: Update php.ini
     template: src=php7.3-php.ini.j2 dest=/etc/php/7.3/fpm/php.ini owner=root group=root mode=0644
     notify: reload php7.3-fpm
+
   tags: php-fpm
-  when: (item.has_wordpress is defined and item.has_wordpress) or (item.needs_php is defined and item.needs_php)
+  when: install_php
 
 # vim: set ts=2 sw=2:

roles/php-fpm/tasks/Ubuntu_18.04.yml

@@ -28,7 +28,8 @@
   - name: Update php.ini
     template: src=php7.2-php.ini.j2 dest=/etc/php/7.2/fpm/php.ini owner=root group=root mode=0644
     notify: reload php7.2-fpm
+
   tags: php-fpm
-  when: (item.has_wordpress is defined and item.has_wordpress) or (item.needs_php is defined and item.needs_php)
+  when: install_php
 
 # vim: set ts=2 sw=2:

roles/php-fpm/tasks/Ubuntu_20.04.yml

@@ -28,7 +28,8 @@
   - name: Update php.ini
     template: src=php7.4-php.ini.j2 dest=/etc/php/7.4/fpm/php.ini owner=root group=root mode=0644
     notify: reload php7.4-fpm
+
   tags: php-fpm
-  when: (item.has_wordpress is defined and item.has_wordpress) or (item.needs_php is defined and item.needs_php)
+  when: install_php
 
 # vim: set ts=2 sw=2:

roles/php-fpm/tasks/main.yml

@@ -4,24 +4,47 @@
 # Ubuntu 20.04 uses PHP 7.4
 # Debian 11 uses PHP 7.4
 
+# If any of the vhosts on this host need WordPress then we need to install PHP.
+# This uses selectattr to filter the list of dicts in nginx_vhosts, selecting
+# any that have has_wordpress defined, and has_wordpress set to True.
+#
+# See: https://stackoverflow.com/a/31896249
+- name: Check if any vhost needs WordPress
+  set_fact:
+    install_php: True
+  when: "nginx_vhosts | selectattr('has_wordpress', 'defined') | selectattr('has_wordpress', 'equalto', True) | list | length > 0"
+
+# Legacy, was only for Piwik, but leaving for now.
+- name: Check if any vhost needs PHP
+  set_fact:
+    install_php: True
+  when: "nginx_vhosts | selectattr('needs_php', 'defined') | selectattr('needs_php', 'equalto', True) | list | length > 0"
+
+# If install_php has not been set, then we assume no vhosts need PHP. This is
+# a bit hacky, but it's the closest we come to an if/then/else.
+- name: Set install_php to False
+  set_fact:
+    install_php: False
+  when: install_php is not defined
+
 - name: Configure php-fpm on Ubuntu 18.04
   include_tasks: Ubuntu_18.04.yml
-  when: ansible_distribution == 'Ubuntu' and ansible_distribution_version is version('18.04', '==')
+  when: ansible_distribution == 'Ubuntu' and ansible_distribution_version is version('18.04', '==') and install_php
   tags: php-fpm
 
 - name: Configure php-fpm on Debian 10
   include_tasks: Debian_10.yml
-  when: ansible_distribution == 'Debian' and ansible_distribution_version is version('10', '==')
+  when: ansible_distribution == 'Debian' and ansible_distribution_version is version('10', '==') and install_php
   tags: php-fpm
 
 - name: Configure php-fpm on Ubuntu 20.04
   include_tasks: Ubuntu_20.04.yml
-  when: ansible_distribution == 'Ubuntu' and ansible_distribution_version is version('20.04', '==')
+  when: ansible_distribution == 'Ubuntu' and ansible_distribution_version is version('20.04', '==') and install_php
   tags: php-fpm
 
 - name: Configure php-fpm on Debian 11
   include_tasks: Ubuntu_20.04.yml
-  when: ansible_distribution == 'Debian' and ansible_distribution_version is version('11', '==')
+  when: ansible_distribution == 'Debian' and ansible_distribution_version is version('11', '==') and install_php
   tags: php-fpm
 
 # vim: set ts=2 sw=2: