Introduce PredicateMemoization cop and fix offenses

with StrongMemoize

3 files changed, 28 insertions, 11 deletions

diff --git a/app/models/concerns/resolvable_discussion.rb b/app/models/concerns/resolvable_discussion.rb
index b6c7b6735b9..6a2cb80b6d5 100644
--- a/app/models/concerns/resolvable_discussion.rb
+++ b/app/models/concerns/resolvable_discussion.rb
@@ -1,5 +1,6 @@
 module ResolvableDiscussion
   extend ActiveSupport::Concern
+  include ::Gitlab::Utils::StrongMemoize
 
   included do
     # A number of properties of this `Discussion`, like `first_note` and `resolvable?`, are memoized.
@@ -31,27 +32,35 @@ module ResolvableDiscussion
   end
 
   def resolvable?
-    @resolvable ||= potentially_resolvable? && notes.any?(&:resolvable?)
+    strong_memoize(:resolvable) do
+      potentially_resolvable? && notes.any?(&:resolvable?)
+    end
   end
 
   def resolved?
-    @resolved ||= resolvable? && notes.none?(&:to_be_resolved?)
+    strong_memoize(:resolved) do
+      resolvable? && notes.none?(&:to_be_resolved?)
+    end
   end
 
   def first_note
-    @first_note ||= notes.first
+    notes.first
   end
 
   def first_note_to_resolve
     return unless resolvable?
 
-    @first_note_to_resolve ||= notes.find(&:to_be_resolved?) # rubocop:disable Gitlab/ModuleWithInstanceVariables
+    strong_memoize(:first_note_to_resolve) do
+      notes.find(&:to_be_resolved?)
+    end
   end
 
   def last_resolved_note
     return unless resolved?
 
-    @last_resolved_note ||= resolved_notes.sort_by(&:resolved_at).last # rubocop:disable Gitlab/ModuleWithInstanceVariables
+    strong_memoize(:last_resolved_note) do
+      resolved_notes.sort_by(&:resolved_at).last
+    end
   end
 
   def resolved_notes
diff --git a/app/models/project.rb b/app/models/project.rb
index 029f2da2e4e..7ab7df4fdcd 100644
--- a/app/models/project.rb
+++ b/app/models/project.rb
@@ -20,6 +20,7 @@ class Project < ActiveRecord::Base
   include GroupDescendant
   include Gitlab::SQL::Pattern
   include DeploymentPlatform
+  include ::Gitlab::Utils::StrongMemoize
 
   extend Gitlab::ConfigHelper
   extend Gitlab::CurrentSettings
@@ -993,9 +994,13 @@ class Project < ActiveRecord::Base
   end
 
   def repo_exists?
-    @repo_exists ||= repository.exists?
-  rescue
-    @repo_exists = false
+    strong_memoize(:repo_exists) do
+      begin
+        repository.exists?
+      rescue
+        false
+      end
+    end
   end
 
   def root_ref?(branch)
diff --git a/app/models/repository.rb b/app/models/repository.rb
index d27212b2058..8e9f33c174c 100644
--- a/app/models/repository.rb
+++ b/app/models/repository.rb
@@ -895,15 +895,18 @@ class Repository
     branch = Gitlab::Git::Branch.find(self, branch_or_name)
 
     if branch
-      @root_ref_sha ||= commit(root_ref).sha
-      same_head = branch.target == @root_ref_sha
-      merged = ancestor?(branch.target, @root_ref_sha)
+      same_head = branch.target == root_ref_sha
+      merged = ancestor?(branch.target, root_ref_sha)
       !same_head && merged
     else
       nil
     end
   end
 
+  def root_ref_sha
+    @root_ref_sha ||= commit(root_ref).sha
+  end
+
   delegate :merged_branch_names, to: :raw_repository
 
   def merge_base(first_commit_id, second_commit_id)