Merge rules variables and files

prometheus/defaults/main.yml

 ---
 prometheus_args: ""
-prometheus:
-  rules:
-    # These variables intentionally left null.  They need to exist, so that the
-    # template works, but they need to have a value (empty string does not
-    # work).
-    alert: null
-    recording: null
+# This variable intentionally left null.  They need to exist, so that the
+# template works, but they need to have a value (empty string does not work).
+prometheus_rules: null

prometheus/tasks/main.yml

@@ -43,12 +43,9 @@
 
 - name: Configure rules
   template:
-    src: "{{ item }}_rules.yml.j2"
-    dest: "/etc/prometheus/rules/ansible_{{ item }}.yml"
+    src: "rules.yml.j2"
+    dest: "/etc/prometheus/rules/ansible_rules.yml"
     validate: "promtool check rules %s"
-  with_items:
-    - alert
-    - recording
   notify:
     - Reload prometheus
   tags:

prometheus/templates/alert_rules.yml.j2

-{{ prometheus.rules.alert|to_nice_yaml }}

prometheus/templates/recording_rules.yml.j2

-{{ prometheus.rules.recording|to_nice_yaml }}

prometheus/templates/rules.yml.j2

+{{ prometheus_rules|to_nice_yaml|replace('[[', '{{')|replace(']]', '}}') }}