Method for returning issues readable by a user

The method Ability.issues_readable_by_user takes a list of users and an
optional user and returns an Array of issues readable by said user. This
method in turn is used by
Banzai::ReferenceParser::IssueParser#nodes_visible_to_user so this
method no longer needs to get all the available abilities just to check
if a user has the "read_issue" ability.

To test this I benchmarked an issue with 222 comments on my development
environment. Using these changes the time spent in nodes_visible_to_user
was reduced from around 120 ms to around 40 ms.

1 files changed, 10 insertions, 0 deletions

diff --git a/app/models/ability.rb b/app/models/ability.rb
index e47c5539f60..d95a2507199 100644
--- a/app/models/ability.rb
+++ b/app/models/ability.rb
@@ -47,6 +47,16 @@ class Ability
       end
     end
 
+    # Returns an Array of Issues that can be read by the given user.
+    #
+    # issues - The issues to reduce down to those readable by the user.
+    # user - The User for which to check the issues
+    def issues_readable_by_user(issues, user = nil)
+      return issues if user && user.admin?
+
+      issues.select { |issue| issue.visible_to_user?(user) }
+    end
+
     # List of possible abilities for anonymous user
     def anonymous_abilities(user, subject)
       if subject.is_a?(PersonalSnippet)