[PR #1627/3cf69cd4 backport][stable-4] Fix KeyError when Description is not present in ssm_parameter

changelogs/fragments/1627-ssm_parameter-KeyError-when-adding-description.yml

@@ -0,0 +1,2 @@
+bugfixes:
+  - ssm_parameter - Fix a ``KeyError`` when adding a description to an existing parameter (https://github.com/ansible-collections/community.aws/issues/1471).

plugins/modules/aws_ssm_parameter_store.py

@@ -380,7 +380,7 @@ def create_update_parameter(client, module):
                 except (botocore.exceptions.ClientError, botocore.exceptions.BotoCoreError) as e:
                     module.fail_json_aws(e, msg="getting description value")
 
-                if describe_existing_parameter['Description'] != args['Description']:
+                if describe_existing_parameter.get('Description') != args['Description']:
                     (changed, response) = update_parameter(client, module, **args)
         if changed:
             _wait_updated(client, module, module.params.get('name'), original_version)

tests/integration/targets/aws_ssm_parameter_store/tasks/main.yml

@@ -415,6 +415,30 @@
       that:
       - result is not changed
 
+  - name: Create key/value pair in aws parameter store with no description
+    aws_ssm_parameter_store:
+      name: '{{ simple_name }}'
+      value: '{{ simple_value }}'
+    register: result
+
+  - assert:
+      that:
+      - result is changed
+      - '"description" not in result.parameter_metadata'
+
+  - name: Add a description
+    aws_ssm_parameter_store:
+      name: '{{ simple_name }}'
+      value: '{{ simple_value }}'
+      description: '{{ simple_description }}'
+    register: result
+
+  - assert:
+      that:
+        - result is changed
+        - '"description" in result.parameter_metadata'
+        - result.parameter_metadata.description == simple_description
+
   always:
   # ============================================================
   - name: Delete remaining key/value pairs in aws parameter store