Add support for dry run (#245)

Add support for dry run

SUMMARY

Kubernetes server-side dry run will be used when the kubernetes client
version is >=18.20.0. For older versions of the client, the existing
client side speculative change implementation will be used.
The effect of this change should be mostly transparent to the end user
and is reflected in the fact the tests have not changed but should still
pass. With this change, there are a few edge cases that will be
improved. One example of these edge cases is to use check mode on an
existing Service resource. With dry run this will correctly report no
changes, while the older client side implementation will erroneously
report changes to the port spec.

ISSUE TYPE


Feature Pull Request

COMPONENT NAME

ADDITIONAL INFORMATION

Reviewed-by: Gonéri Le Bouder <goneri@lebouder.net>
Reviewed-by: Mike Graves <mgraves@redhat.com>
Reviewed-by: Alina Buzachis <None>
Reviewed-by: None <None>
Reviewed-by: None <None>

plugins/modules/k8s_json_patch.py

@@ -234,13 +234,16 @@ def execute_module(k8s_module, module):
         msg = 'Failed to retrieve requested object: {0}'.format(to_native(exc))
         module.fail_json(msg=build_error_msg(kind, name, msg), error='', status='', reason='')
 
-    if module.check_mode:
+    if module.check_mode and not k8s_module.supports_dry_run:
         obj, error = json_patch(existing.to_dict(), patch)
         if error:
             module.fail_json(**error)
     else:
+        params = {}
+        if module.check_mode:
+            params["dry_run"] = "All"
         try:
-            obj = resource.patch(patch, name=name, namespace=namespace, content_type="application/json-patch+json").to_dict()
+            obj = resource.patch(patch, name=name, namespace=namespace, content_type="application/json-patch+json", **params).to_dict()
         except DynamicApiError as exc:
             msg = "Failed to patch existing object: {0}".format(exc.body)
             module.fail_json(msg=msg, error=exc.status, status=exc.status, reason=exc.reason)