Method for returning issues readable by a userability-batch-issue-checking

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, 28 insertions, 0 deletions

diff --git a/app/models/issue.rb b/app/models/issue.rb
index d9428ebc9fb..11f734cfc6d 100644
--- a/app/models/issue.rb
+++ b/app/models/issue.rb
@@ -230,6 +230,34 @@ class Issue < ActiveRecord::Base
       self.closed_by_merge_requests(current_user).empty?
   end
 
+  # Returns `true` if the current issue can be viewed by either a logged in User
+  # or an anonymous user.
+  def visible_to_user?(user = nil)
+    user ? readable_by?(user) : publicly_visible?
+  end
+
+  # Returns `true` if the given User can read the current Issue.
+  def readable_by?(user)
+    if user.admin?
+      true
+    elsif project.owner == user
+      true
+    elsif confidential?
+      author == user ||
+        assignee == user ||
+        project.team.member?(user, Gitlab::Access::REPORTER)
+    else
+      project.public? ||
+        project.internal? && !user.external? ||
+        project.team.member?(user)
+    end
+  end
+
+  # Returns `true` if this Issue is visible to everybody.
+  def publicly_visible?
+    project.public? && !confidential?
+  end
+
   def overdue?
     due_date.try(:past?) || false
   end