Log QA resource reuse

Changes the debug log message shown when a resource is fabricated.
- "Built" as previously, when a resource is created.
- "Retrieved" when an existing resource is fetched.
- "Retrieved for reuse" when an existing resource is fetched as a
  reusable resource.

Adds a ReusableGroup class so that ResuableProject is truly reusable
(otherwise ResuableProject would create a new group in a different
project each time).

qa/qa/resource/api_fabricator.rb

@@ -63,6 +63,10 @@ module QA
         process_api_response(parse_body(response))
       end
 
+      def api_fabrication_http_method
+        @api_fabrication_http_method ||= :post
+      end
+
       private
 
       def resource_web_url(resource)
@@ -85,6 +89,8 @@ module QA
           raise ResourceNotFoundError, "Resource at #{request.mask_url} could not be found (#{response.code}): `#{response}`."
         end
 
+        @api_fabrication_http_method = :get # rubocop:disable Gitlab/ModuleWithInstanceVariables
+
         response
       end
 

qa/qa/resource/base.rb

@@ -94,10 +94,20 @@ module QA
               nil
             end
 
+            fabrication_http_method = if resource.api_fabrication_http_method == :get
+                                        if self.include?(Reusable)
+                                          "Retrieved for reuse"
+                                        else
+                                          "Retrieved"
+                                        end
+                                      else
+                                        "Built"
+                                      end
+
             Support::FabricationTracker.save_fabrication(:"#{method}_fabrication", fabrication_time)
             Runtime::Logger.debug do
               msg = ["==#{'=' * parents.size}>"]
-              msg << "Built a #{name}"
+              msg << "#{fabrication_http_method} a #{name}"
               msg << resource_identifier if resource_identifier
               msg << "as a dependency of #{parents.last}" if parents.any?
               msg << "via #{method}"

qa/qa/resource/reusable_group.rb

+# frozen_string_literal: true
+
+module QA
+  module Resource
+    class ReusableGroup < Group
+      prepend Reusable
+
+      def initialize
+        super
+
+        @path = "reusable_group"
+        @description = "QA reusable group"
+        @reuse_as = :default_group
+      end
+
+      # Confirms that the group can be reused
+      #
+      # @return [nil] returns nil unless an error is raised
+      def validate_reuse_preconditions
+        unless reused_path_unique?
+          raise ResourceReuseError,
+            "Reusable groups must have the same name. The group reused as #{reuse_as} has the path '#{path}' but it should be '#{self.class.resources[reuse_as].path}'"
+        end
+      end
+
+      # Confirms that reuse of the resource did not change it in a way that breaks later reuse. This raises an error if
+      # the current group path doesn't match the original path.
+      def validate_reuse
+        reload!
+
+        if api_resource[:path] != @path
+          raise ResourceReuseError, "The group now has the path '#{api_resource[:path]}' but it should be '#{path}'"
+        end
+      end
+
+      # Checks if the group is being reused with the same path.
+      #
+      # @return [Boolean] true if the group's path is different from another group with the same reuse symbol (reuse_as)
+      def reused_path_unique?
+        return true unless self.class.resources.key?(reuse_as)
+
+        self.class.resources[reuse_as].path == path
+      end
+
+      # Overrides QA::Resource::Group#remove_via_api! to log a debug message stating that removal will happen after
+      # the suite completes rather than now.
+      #
+      # @return [nil]
+      def remove_via_api!
+        QA::Runtime::Logger.debug("#{self.class.name} - deferring removal until after suite")
+      end
+    end
+  end
+end

qa/qa/resource/reusable_project.rb

@@ -5,6 +5,12 @@ module QA
     class ReusableProject < Project
       prepend Reusable
 
+      attribute :group do
+        ReusableGroup.fabricate_via_api! do |resource|
+          resource.api_client = api_client
+        end
+      end
+
       def initialize
         super