docker_swarm_service: Added default value for mounts.source (#58039)

* Added default value for mounts.source

* Added the changelog fragment

* Added tests

* Fixed separators

* Moved the teardown section at the end

changelogs/fragments/58039-docker_swarm_service-fix-resource-lookup.yaml

@@ -0,0 +1,2 @@
+bugfixes:
+  - docker_swarm_service - fix resource lookup if mounts.source="".

lib/ansible/modules/cloud/docker/docker_swarm_service.py

@@ -2230,7 +2230,7 @@ class DockerServiceManager(object):
                     (key.lower(), value) for key, value in driver_config.items()
                 ) or None
                 ds.mounts.append({
-                    'source': mount_data['Source'],
+                    'source': mount_data.get('Source', ''),
                     'type': mount_data['Type'],
                     'target': mount_data['Target'],
                     'readonly': mount_data.get('ReadOnly'),

test/integration/targets/docker_swarm_service/tasks/tests/mounts.yml

@@ -509,6 +509,53 @@
     - "'Minimum version required' in mounts_tmpfs_size_1.msg"
   when: docker_py_version is version('2.6.0', '<')
 
+####################################################################
+## mounts.source ###################################################
+####################################################################
+
+- name: mounts.source (empty for tmpfs)
+  docker_swarm_service:
+    name: "{{ service_name }}"
+    image: alpine:3.8
+    resolve_image: no
+    command: '/bin/sh -v -c "sleep 10m"'
+    mounts:
+      - source: ""
+        target: "/tmp/{{ volume_name_1 }}"
+        type: "tmpfs"
+  register: mounts_tmpfs_source_1
+  ignore_errors: yes
+
+- name: mounts.source (empty for tmpfs idempotency)
+  docker_swarm_service:
+    name: "{{ service_name }}"
+    image: alpine:3.8
+    resolve_image: no
+    command: '/bin/sh -v -c "sleep 10m"'
+    mounts:
+      - source: ""
+        target: "/tmp/{{ volume_name_1 }}"
+        type: "tmpfs"
+  register: mounts_tmpfs_source_2
+  ignore_errors: yes
+
+- name: cleanup
+  docker_swarm_service:
+    name: "{{ service_name }}"
+    state: absent
+  diff: no
+
+- assert:
+    that:
+      - mounts_tmpfs_source_1 is changed
+      - mounts_tmpfs_source_2 is not changed
+  when: docker_py_version is version('2.6.0', '>=')
+- assert:
+    that:
+    - mounts_tmpfs_source_1 is failed
+    - "'Minimum version required' in mounts_tmpfs_source_1.msg"
+  when: docker_py_version is version('2.6.0', '<')
+
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