Using rescue to hold AWS::SNS::Client exception

That will allow to evaluate the "should exist" statement and raise the Awspec::NoExistingResource anywhere else.

doc/resource_types.md

@@ -2551,7 +2551,7 @@ end
 ```
 
 
-### its(:vpc_id), its(:db_instance_identifier), its(:db_instance_class), its(:engine), its(:db_instance_status), its(:master_username), its(:db_name), its(:endpoint), its(:allocated_storage), its(:instance_create_time), its(:preferred_backup_window), its(:backup_retention_period), its(:db_security_groups), its(:availability_zone), its(:preferred_maintenance_window), its(:pending_modified_values), its(:latest_restorable_time), its(:multi_az), its(:engine_version), its(:auto_minor_version_upgrade), its(:read_replica_source_db_instance_identifier), its(:read_replica_db_instance_identifiers), its(:read_replica_db_cluster_identifiers), its(:license_model), its(:iops), its(:character_set_name), its(:secondary_availability_zone), its(:publicly_accessible), its(:status_infos), its(:storage_type), its(:tde_credential_arn), its(:db_instance_port), its(:db_cluster_identifier), its(:storage_encrypted), its(:kms_key_id), its(:dbi_resource_id), its(:ca_certificate_identifier), its(:domain_memberships), its(:copy_tags_to_snapshot), its(:monitoring_interval), its(:enhanced_monitoring_resource_arn), its(:monitoring_role_arn), its(:promotion_tier), its(:db_instance_arn), its(:timezone), its(:iam_database_authentication_enabled), its(:performance_insights_enabled), its(:performance_insights_kms_key_id), its(:performance_insights_retention_period), its(:enabled_cloudwatch_logs_exports), its(:processor_features), its(:deletion_protection), its(:listener_endpoint)
+### its(:vpc_id), its(:db_instance_identifier), its(:db_instance_class), its(:engine), its(:db_instance_status), its(:master_username), its(:db_name), its(:endpoint), its(:allocated_storage), its(:instance_create_time), its(:preferred_backup_window), its(:backup_retention_period), its(:db_security_groups), its(:availability_zone), its(:preferred_maintenance_window), its(:pending_modified_values), its(:latest_restorable_time), its(:multi_az), its(:engine_version), its(:auto_minor_version_upgrade), its(:read_replica_source_db_instance_identifier), its(:read_replica_db_instance_identifiers), its(:read_replica_db_cluster_identifiers), its(:license_model), its(:iops), its(:character_set_name), its(:secondary_availability_zone), its(:publicly_accessible), its(:status_infos), its(:storage_type), its(:tde_credential_arn), its(:db_instance_port), its(:db_cluster_identifier), its(:storage_encrypted), its(:kms_key_id), its(:dbi_resource_id), its(:ca_certificate_identifier), its(:domain_memberships), its(:copy_tags_to_snapshot), its(:monitoring_interval), its(:enhanced_monitoring_resource_arn), its(:monitoring_role_arn), its(:promotion_tier), its(:db_instance_arn), its(:timezone), its(:iam_database_authentication_enabled), its(:performance_insights_enabled), its(:performance_insights_kms_key_id), its(:performance_insights_retention_period), its(:enabled_cloudwatch_logs_exports), its(:processor_features), its(:deletion_protection), its(:associated_roles), its(:listener_endpoint)
 ### :unlock: Advanced use
 
 `rds` can use `Aws::RDS::DBInstance` resource (see http://docs.aws.amazon.com/sdkforruby/api/Aws/RDS/DBInstance.html).

lib/awspec/helper/finder/sns_topic.rb

@@ -30,16 +30,52 @@ def to_s
       end
 
       def find_sns_topic(topic_arn)
-        response = sns_client.get_topic_attributes({ topic_arn: topic_arn })
-        SnsTopic.new(response.attributes)
+        # Find a SNS topic by searching from it's ARN.
+        # Expects as parameter the SNS topic ARN.
+        # Returns a Awspec::Helper::Finder::SNSTopic::SnsTopic if the topic is
+        # found, nil otherwise.
+        # If the SNS topic does not exist, AWS SDK throws an exception
+        # which is acceptable in some cases, but in others will generate a
+        # NoMethodFound during tests execution.
+        # In order to avoid that and follow a uniform interface, the exception
+        # will be captured and nil will be returned instead.
+        # By convention, the returned object will be checked (see check_existence
+        # method from Awspec::Type::Base class for an example) and an exception
+        # Awspec::NoExistingResource will be raised.
+        begin
+          response = sns_client.get_topic_attributes({ topic_arn: topic_arn })
+          puts response
+          topic = SnsTopic.new(response.attributes)
+        rescue Aws::SNS::Errors::NotFound
+          topic = nil
+        end
+
+        topic
       end
 
       def find_sns_topic_subs(topic_arn)
-        response = sns_client.list_subscriptions_by_topic({ topic_arn: topic_arn })
-        subscriptions = {}
-        response.subscriptions.each do |subscribed|
-          subscriptions[subscribed['subscription_arn'].to_sym] = subscribed
+        # Find a SNS topic subscribers by searching from it's ARN.
+        # Expects as parameter the SNS topic ARN.
+        # Returns a map (with keys as the subscribed ARN and the value instances
+        # of respective objects) if the topic is found, nil otherwise.
+        # If the SNS topic does not exist, AWS SDK throws an exception
+        # which is acceptable in some cases, but in others will generate a
+        # NoMethodFound during tests execution.
+        # In order to avoid that and follow a uniform interface, the exception
+        # will be captured and nil will be returned instead.
+        # By convention, the returned object will be checked (see check_existence
+        # method from Awspec::Type::Base class for an example) and an exception
+        # Awspec::NoExistingResource will be raised.
+        begin
+          response = sns_client.list_subscriptions_by_topic({ topic_arn: topic_arn })
+          subscriptions = {}
+          response.subscriptions.each do |subscribed|
+            subscriptions[subscribed['subscription_arn'].to_sym] = subscribed
+          end
+        rescue Aws::SNS::Errors::NotFound
+          subscriptions = nil
         end
+
         subscriptions
       end
     end

lib/awspec/type/sns_topic.rb

@@ -34,6 +34,7 @@ def subscribed(subscribed_arn)
     end
 
     def method_missing(method_name)
+      check_existence
       # delegates the method invocation to Awspec::Helper::Finder::SnsTopic::SnsTopic class
       @resource_via_client.send method_name
     end
@@ -42,6 +43,7 @@ def method_missing(method_name)
 
     def fetch_subscriptions
       @subscriptions = find_sns_topic_subs(@topic_arn) if @subscriptions.nil?
+      raise Awspec::NoExistingResource.new(self.class, @display_name) if @subscriptions.nil?
       @subscriptions
     end
   end