update-json-file: avoid failure when destination does not exists

It is perfectly valid to want to add a value to a file that
does not exist yet, even the path may be missing.

This fixes last night regression when installing docker no longer
creates the /etc/docker folder, causing our MTU update to fail.

Change-Id: I0f037d1d6664de3c3b777aaf6da9cd7c3e8bb15f
Reference: https://review.rdoproject.org/zuul/builds?job_name=tox-py36-ci-config&project=rdo-infra/ci-config

roles/update-json-file/README.rst

@@ -46,3 +46,7 @@ idempotent and will write the file each time.
 .. zuul:rolevar:: update_json_file_group
 
    The group for the combined file.
+
+.. zuul:rolevar:: update_json_dir_mode
+
+   The mode for the directory if that does not already exists.

roles/update-json-file/tasks/main.yaml

@@ -28,6 +28,25 @@
     var: _config
   when: update_json_file_debug
 
+- name: Assure we have a target directory
+  when: update_json_file_name | dirname
+  block:
+    - name: Check if target directory exists
+      stat:
+        path: "{{ update_json_file_name | dirname }}"
+      register: _result
+
+    - name: Create target directory
+      file:
+        path: "{{ update_json_file_name | dirname }}"
+        state: directory
+        mode: '{{ update_json_dir_mode | default(omit) }}'
+        owner: '{{ update_json_file_owner | default(omit) }}'
+        group: '{{ update_json_file_group | default(omit) }}'
+        recurse: yes
+      become: '{{ update_json_file_become }}'
+      when: not _result.stat.exists
+
 - name: Save new file
   copy:
     content: "{{ _config | to_nice_json }}"

test-playbooks/update-json-file.yaml

@@ -4,7 +4,7 @@
     - include_role:
         name: update-json-file
       vars:
-        update_json_file_name: test.json
+        update_json_file_name: some/test.json
         update_json_file_default:
           foo: bar
         update_json_file_combine:
@@ -14,7 +14,7 @@
     - include_role:
         name: update-json-file
       vars:
-        update_json_file_name: test.json
+        update_json_file_name: some/test.json
         update_json_file_combine:
           new: content
           a:
@@ -25,7 +25,7 @@
 
     - name: Load resulting merged file
       slurp:
-        path: 'test.json'
+        path: 'some/test.json'
       register: _file
 
     - name: Parse merged file