docker_container: improve image finding / change detection (#62971)

* Improve image finding / change detection.

* Checked wrong object.

* Improve behavior. (Let docker daemon sort this out.)

* Add changelog.

* Add simple test.

* Fix image name.

* Use new docker_image params.

* Rewrite.

changelogs/fragments/62971-docker_container-image-finding.yml

@@ -0,0 +1,2 @@
+bugfixes:
+- "docker_container - make sure that when image is missing, check mode indicates a change (image will be pulled)."

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

@@ -2640,8 +2640,8 @@ class ContainerManager(DockerBaseClass):
             if not tag:
                 tag = "latest"
             image = self.client.find_image(repository, tag)
-            if not self.check_mode:
-                if not image or self.parameters.pull:
+            if not image or self.parameters.pull:
+                if not self.check_mode:
                     self.log("Pull the image.")
                     image, alreadyToLatest = self.client.pull_image(repository, tag)
                     if alreadyToLatest:
@@ -2649,6 +2649,12 @@ class ContainerManager(DockerBaseClass):
                     else:
                         self.results['changed'] = True
                         self.results['actions'].append(dict(pulled_image="%s:%s" % (repository, tag)))
+                elif not image:
+                    # If the image isn't there, claim we'll pull.
+                    # (Implicitly: if the image is there, claim it already was latest.)
+                    self.results['changed'] = True
+                    self.results['actions'].append(dict(pulled_image="%s:%s" % (repository, tag)))
+
         self.log("image")
         self.log(image, pretty_print=True)
         return image

test/integration/targets/docker_container/tasks/tests/image-ids.yml

@@ -9,7 +9,7 @@
 - name: Pull images
   docker_image:
     name: "{{ image }}"
-    pull: true
+    source: pull
   loop:
     - "hello-world:latest"
     - "alpine:3.8"
@@ -63,6 +63,28 @@
     force_kill: yes
   register: create_4
 
+- name: Untag image
+  # Image will not be deleted since the container still uses it
+  docker_image:
+    name: alpine:3.8
+    force_absent: yes
+    state: absent
+
+- name: Create container with alpine image via name (check mode, will pull, same image)
+  docker_container:
+    image: alpine:3.8
+    name: "{{ cname }}"
+    state: present
+  register: create_5
+  check_mode: yes
+
+- name: Create container with alpine image via name (will pull, same image)
+  docker_container:
+    image: alpine:3.8
+    name: "{{ cname }}"
+    state: present
+  register: create_6
+
 - name: Cleanup
   docker_container:
     name: "{{ cname }}"
@@ -76,6 +98,10 @@
       - create_2 is not changed
       - create_3 is changed
       - create_4 is not changed
+      - create_5 is changed
+      - create_6 is changed
+      - create_6.container.Image == image_info.images[1].Id
+      - create_6.container.Id == create_4.container.Id  # make sure container wasn't recreated
 
 - name: set Digests
   set_fact: