Put in documented default for gcp_compute filters (#50025)

changelogs/fragments/50025-gcp_compute_filters_default.yml

@@ -0,0 +1,2 @@
+bugfixes:
+  - gcp_compute inventory plugin - apply documented default when one is not provided.

docs/docsite/rst/scenario_guides/guide_gce.rst

@@ -145,7 +145,6 @@ Here's an example of a valid inventory file:
     plugin: gcp_compute
     projects:
       - graphite-playground
-    filters:
     auth_kind: serviceaccount
     service_account_file: /home/alexstephen/my_account.json
 

lib/ansible/plugins/inventory/gcp_compute.py

@@ -337,6 +337,10 @@ class InventoryModule(BaseInventoryPlugin, Constructable, Cacheable):
         if not isinstance(config_data['projects'], list):
             raise AnsibleParserError("Projects must be a list in GCP inventory YAML files")
 
+        # add in documented defaults
+        if 'filters' not in config_data:
+            config_data['filters'] = None
+
         projects = config_data['projects']
         zones = config_data.get('zones')
         config_data['scopes'] = ['https://www.googleapis.com/auth/compute']