hcloud_volume attach step should be idempotent (#56906)

changelogs/fragments/56906-hcloud_volume_attaching_idempotent.yaml

@@ -0,0 +1,2 @@
+bugfixes:
+  - hcloud_volume - Fix idempotency when attaching a server to a volume.

lib/ansible/modules/cloud/hcloud/hcloud_volume.py

@@ -232,7 +232,7 @@ class AnsibleHcloudVolume(Hcloud):
         server_name = self.module.params.get("server")
         if server_name:
             server = self.client.servers.get_by_name(server_name)
-            if self.hcloud_volume.server != server:
+            if self.hcloud_volume.server is None or self.hcloud_volume.server.name != server.name:
                 if not self.module.check_mode:
                     automount = self.module.params.get("automount", False)
                     self.hcloud_volume.attach(server, automount=automount).wait_until_finished()

test/integration/targets/hcloud_volume/tasks/main.yml

@@ -8,11 +8,11 @@
     image: ubuntu-18.04
     state: started
     location: "fsn1"
-  register: main_server
+  register: vol_server
 - name: verify setup server
   assert:
     that:
-      - main_server is changed
+      - vol_server is changed
 
 - name: test missing size parameter on create Volume
   hcloud_volume:
@@ -86,7 +86,17 @@
     that:
       - volume is changed
       - volume.hcloud_volume.server == "{{hcloud_server_name}}"
-      - main_server is changed
+
+- name: test attach volume idempotence
+  hcloud_volume:
+    name: "{{hcloud_volume_name}}"
+    server: "{{hcloud_server_name}}"
+  register: volume
+- name: verify attach volume idempotence
+  assert:
+    that:
+      - volume is not changed
+      - volume.hcloud_volume.server == "{{hcloud_server_name}}"
 
 - name: test detach volume with checkmode
   hcloud_volume:
@@ -109,7 +119,6 @@
       - volume is changed
       - volume.hcloud_volume.location == "fsn1"
       - volume.hcloud_volume.server != "{{hcloud_server_name}}"
-      - main_server is changed
 
 - name: test update volume label
   hcloud_volume: