Refactor banzai to support referencing from group contextce-backport-3615

22 files changed, 273 insertions, 166 deletions

diff --git a/app/helpers/markup_helper.rb b/app/helpers/markup_helper.rb
index 9d269cb65d6..5c9fb1fa0fc 100644
--- a/app/helpers/markup_helper.rb
+++ b/app/helpers/markup_helper.rb
@@ -86,6 +86,8 @@ module MarkupHelper
     return '' unless text.present?
 
     context[:project] ||= @project
+    context[:group] ||= @group
+
     html = markdown_unsafe(text, context)
     prepare_for_rendering(html, context)
   end
diff --git a/app/models/epic.rb b/app/models/epic.rb
index 62898a02e2d..286b855de3f 100644
--- a/app/models/epic.rb
+++ b/app/models/epic.rb
@@ -1,7 +1,11 @@
 # Placeholder class for model that is implemented in EE
-# It will reserve (ee#3853) '&' as a reference prefix, but the table does not exists in CE
+# It reserves '&' as a reference prefix, but the table does not exists in CE
 class Epic < ActiveRecord::Base
-  # TODO: this will be implemented as part of #3853
-  def to_reference
+  def self.reference_prefix
+    '&'
+  end
+
+  def self.reference_prefix_escaped
+    '&amp;'
   end
 end
diff --git a/lib/banzai/cross_project_reference.rb b/lib/banzai/cross_project_reference.rb
index e2b57adf611..d8fb7705b2a 100644
--- a/lib/banzai/cross_project_reference.rb
+++ b/lib/banzai/cross_project_reference.rb
@@ -11,7 +11,7 @@ module Banzai
     # ref - String reference.
     #
     # Returns a Project, or nil if the reference can't be found
-    def project_from_ref(ref)
+    def parent_from_ref(ref)
       return context[:project] unless ref
 
       Project.find_by_full_path(ref)
diff --git a/lib/banzai/filter/abstract_reference_filter.rb b/lib/banzai/filter/abstract_reference_filter.rb
index 8975395aff1..e7e6a90b5fd 100644
--- a/lib/banzai/filter/abstract_reference_filter.rb
+++ b/lib/banzai/filter/abstract_reference_filter.rb
@@ -82,9 +82,9 @@ module Banzai
         end
       end
 
-      def project_from_ref_cached(ref)
-        cached_call(:banzai_project_refs, ref) do
-          project_from_ref(ref)
+      def from_ref_cached(ref)
+        cached_call("banzai_#{parent_type}_refs".to_sym, ref) do
+          parent_from_ref(ref)
         end
       end
 
@@ -153,15 +153,20 @@ module Banzai
       # have `gfm` and `gfm-OBJECT_NAME` class names attached for styling.
       def object_link_filter(text, pattern, link_content: nil, link_reference: false)
         references_in(text, pattern) do |match, id, project_ref, namespace_ref, matches|
-          project_path = full_project_path(namespace_ref, project_ref)
-          project = project_from_ref_cached(project_path)
+          parent_path = if parent_type == :group
+                          full_group_path(namespace_ref)
+                        else
+                          full_project_path(namespace_ref, project_ref)
+                        end
 
-          if project
+          parent = from_ref_cached(parent_path)
+
+          if parent
             object =
               if link_reference
-                find_object_from_link_cached(project, id)
+                find_object_from_link_cached(parent, id)
               else
-                find_object_cached(project, id)
+                find_object_cached(parent, id)
               end
           end
 
@@ -169,13 +174,13 @@ module Banzai
             title = object_link_title(object)
             klass = reference_class(object_sym)
 
-            data = data_attributes_for(link_content || match, project, object, link: !!link_content)
+            data = data_attributes_for(link_content || match, parent, object, link: !!link_content)
 
             url =
               if matches.names.include?("url") && matches[:url]
                 matches[:url]
               else
-                url_for_object_cached(object, project)
+                url_for_object_cached(object, parent)
               end
 
             content = link_content || object_link_text(object, matches)
@@ -224,17 +229,24 @@ module Banzai
 
       # Returns a Hash containing all object references (e.g. issue IDs) per the
       # project they belong to.
-      def references_per_project
-        @references_per_project ||= begin
+      def references_per_parent
+        @references_per ||= {}
+
+        @references_per[parent_type] ||= begin
           refs = Hash.new { |hash, key| hash[key] = Set.new }
 
           regex = Regexp.union(object_class.reference_pattern, object_class.link_reference_pattern)
 
           nodes.each do |node|
             node.to_html.scan(regex) do
-              project_path = full_project_path($~[:namespace], $~[:project])
+              path = if parent_type == :project
+                       full_project_path($~[:namespace], $~[:project])
+                     else
+                       full_group_path($~[:group])
+                     end
+
               symbol = $~[object_sym]
-              refs[project_path] << symbol if object_class.reference_valid?(symbol)
+              refs[path] << symbol if object_class.reference_valid?(symbol)
             end
           end
 
@@ -244,35 +256,41 @@ module Banzai
 
       # Returns a Hash containing referenced projects grouped per their full
       # path.
-      def projects_per_reference
-        @projects_per_reference ||= begin
+      def parent_per_reference
+        @per_reference ||= {}
+
+        @per_reference[parent_type] ||= begin
           refs = Set.new
 
-          references_per_project.each do |project_ref, _|
-            refs << project_ref
+          references_per_parent.each do |ref, _|
+            refs << ref
           end
 
-          find_projects_for_paths(refs.to_a).index_by(&:full_path)
+          find_for_paths(refs.to_a).index_by(&:full_path)
         end
       end
 
-      def projects_relation_for_paths(paths)
-        Project.where_full_path_in(paths).includes(:namespace)
+      def relation_for_paths(paths)
+        klass = parent_type.to_s.camelize.constantize
+        result = klass.where_full_path_in(paths)
+        return result if parent_type == :group
+
+        result.includes(:namespace) if parent_type == :project
       end
 
       # Returns projects for the given paths.
-      def find_projects_for_paths(paths)
+      def find_for_paths(paths)
         if RequestStore.active?
-          cache = project_refs_cache
+          cache = refs_cache
           to_query = paths - cache.keys
 
           unless to_query.empty?
-            projects = projects_relation_for_paths(to_query)
+            records = relation_for_paths(to_query)
 
             found = []
-            projects.each do |project|
-              ref = project.full_path
-              get_or_set_cache(cache, ref) { project }
+            records.each do |record|
+              ref = record.full_path
+              get_or_set_cache(cache, ref) { record }
               found << ref
             end
 
@@ -284,33 +302,37 @@ module Banzai
 
           cache.slice(*paths).values.compact
         else
-          projects_relation_for_paths(paths)
+          relation_for_paths(paths)
         end
       end
 
-      def current_project_path
-        return unless project
-
-        @current_project_path ||= project.full_path
+      def current_parent_path
+        @current_parent_path ||= parent&.full_path
       end
 
       def current_project_namespace_path
-        return unless project
-
-        @current_project_namespace_path ||= project.namespace.full_path
+        @current_project_namespace_path ||= project&.namespace&.full_path
       end
 
       private
 
       def full_project_path(namespace, project_ref)
-        return current_project_path unless project_ref
+        return current_parent_path unless project_ref
 
         namespace_ref = namespace || current_project_namespace_path
         "#{namespace_ref}/#{project_ref}"
       end
 
-      def project_refs_cache
-        RequestStore[:banzai_project_refs] ||= {}
+      def refs_cache
+        RequestStore["banzai_#{parent_type}_refs".to_sym] ||= {}
+      end
+
+      def parent_type
+        :project
+      end
+
+      def parent
+        parent_type == :project ? project : group
       end
     end
   end
diff --git a/lib/banzai/filter/epic_reference_filter.rb b/lib/banzai/filter/epic_reference_filter.rb
new file mode 100644
index 00000000000..265924abe24
--- /dev/null
+++ b/lib/banzai/filter/epic_reference_filter.rb
@@ -0,0 +1,12 @@
+module Banzai
+  module Filter
+    # The actual filter is implemented in the EE mixin
+    class EpicReferenceFilter < IssuableReferenceFilter
+      self.reference_type = :epic
+
+      def self.object_class
+        Epic
+      end
+    end
+  end
+end
diff --git a/lib/banzai/filter/issuable_reference_filter.rb b/lib/banzai/filter/issuable_reference_filter.rb
new file mode 100644
index 00000000000..7addf09be73
--- /dev/null
+++ b/lib/banzai/filter/issuable_reference_filter.rb
@@ -0,0 +1,31 @@
+module Banzai
+  module Filter
+    class IssuableReferenceFilter < AbstractReferenceFilter
+      def records_per_parent
+        @records_per_project ||= {}
+
+        @records_per_project[object_class.to_s.underscore] ||= begin
+          hash = Hash.new { |h, k| h[k] = {} }
+
+          parent_per_reference.each do |path, parent|
+            record_ids = references_per_parent[path]
+
+            parent_records(parent, record_ids).each do |record|
+              hash[parent][record.iid.to_i] = record
+            end
+          end
+
+          hash
+        end
+      end
+
+      def find_object(parent, iid)
+        records_per_parent[parent][iid]
+      end
+
+      def parent_from_ref(ref)
+        parent_per_reference[ref || current_parent_path]
+      end
+    end
+  end
+end
diff --git a/lib/banzai/filter/issue_reference_filter.rb b/lib/banzai/filter/issue_reference_filter.rb
index ce1ab977d3b..6877cae8c55 100644
--- a/lib/banzai/filter/issue_reference_filter.rb
+++ b/lib/banzai/filter/issue_reference_filter.rb
@@ -8,46 +8,24 @@ module Banzai
     # When external issues tracker like Jira is activated we should not
     # use issue reference pattern, but we should still be able
     # to reference issues from other GitLab projects.
-    class IssueReferenceFilter < AbstractReferenceFilter
+    class IssueReferenceFilter < IssuableReferenceFilter
       self.reference_type = :issue
 
       def self.object_class
         Issue
       end
 
-      def find_object(project, iid)
-        issues_per_project[project][iid]
-      end
-
       def url_for_object(issue, project)
         IssuesHelper.url_for_issue(issue.iid, project, only_path: context[:only_path], internal: true)
       end
 
-      def project_from_ref(ref)
-        projects_per_reference[ref || current_project_path]
-      end
-
-      # Returns a Hash containing the issues per Project instance.
-      def issues_per_project
-        @issues_per_project ||= begin
-          hash = Hash.new { |h, k| h[k] = {} }
-
-          projects_per_reference.each do |path, project|
-            issue_ids = references_per_project[path]
-            issues = project.issues.where(iid: issue_ids.to_a)
-
-            issues.each do |issue|
-              hash[project][issue.iid.to_i] = issue
-            end
-          end
-
-          hash
-        end
-      end
-
       def projects_relation_for_paths(paths)
         super(paths).includes(:gitlab_issue_tracker_service)
       end
+
+      def parent_records(parent, ids)
+        parent.issues.where(iid: ids.to_a)
+      end
     end
   end
 end
diff --git a/lib/banzai/filter/label_reference_filter.rb b/lib/banzai/filter/label_reference_filter.rb
index 5364984c9d3..d5360ad8f68 100644
--- a/lib/banzai/filter/label_reference_filter.rb
+++ b/lib/banzai/filter/label_reference_filter.rb
@@ -33,7 +33,7 @@ module Banzai
       end
 
       def find_label(project_ref, label_id, label_name)
-        project = project_from_ref(project_ref)
+        project = parent_from_ref(project_ref)
         return unless project
 
         label_params = label_params(label_id, label_name)
@@ -66,7 +66,7 @@ module Banzai
 
       def object_link_text(object, matches)
         project_path     = full_project_path(matches[:namespace], matches[:project])
-        project_from_ref = project_from_ref_cached(project_path)
+        project_from_ref = from_ref_cached(project_path)
         reference        = project_from_ref.to_human_reference(project)
         label_suffix     = " <i>in #{reference}</i>" if reference.present?
 
diff --git a/lib/banzai/filter/merge_request_reference_filter.rb b/lib/banzai/filter/merge_request_reference_filter.rb
index 0eab865ac04..b3cfa97d0e0 100644
--- a/lib/banzai/filter/merge_request_reference_filter.rb
+++ b/lib/banzai/filter/merge_request_reference_filter.rb
@@ -4,48 +4,19 @@ module Banzai
     # to merge requests that do not exist are ignored.
     #
     # This filter supports cross-project references.
-    class MergeRequestReferenceFilter < AbstractReferenceFilter
+    class MergeRequestReferenceFilter < IssuableReferenceFilter
       self.reference_type = :merge_request
 
       def self.object_class
         MergeRequest
       end
 
-      def find_object(project, iid)
-        merge_requests_per_project[project][iid]
-      end
-
       def url_for_object(mr, project)
         h = Gitlab::Routing.url_helpers
         h.project_merge_request_url(project, mr,
                                             only_path: context[:only_path])
       end
 
-      def project_from_ref(ref)
-        projects_per_reference[ref || current_project_path]
-      end
-
-      # Returns a Hash containing the merge_requests per Project instance.
-      def merge_requests_per_project
-        @merge_requests_per_project ||= begin
-          hash = Hash.new { |h, k| h[k] = {} }
-
-          projects_per_reference.each do |path, project|
-            merge_request_ids = references_per_project[path]
-
-            merge_requests = project.merge_requests
-              .where(iid: merge_request_ids.to_a)
-              .includes(target_project: :namespace)
-
-            merge_requests.each do |merge_request|
-              hash[project][merge_request.iid.to_i] = merge_request
-            end
-          end
-
-          hash
-        end
-      end
-
       def object_link_text_extras(object, matches)
         extras = super
 
@@ -61,6 +32,12 @@ module Banzai
 
         extras
       end
+
+      def parent_records(parent, ids)
+        parent.merge_requests
+          .where(iid: ids.to_a)
+          .includes(target_project: :namespace)
+      end
     end
   end
 end
diff --git a/lib/banzai/filter/milestone_reference_filter.rb b/lib/banzai/filter/milestone_reference_filter.rb
index bb5da310e09..2a6b0964ac5 100644
--- a/lib/banzai/filter/milestone_reference_filter.rb
+++ b/lib/banzai/filter/milestone_reference_filter.rb
@@ -38,7 +38,7 @@ module Banzai
 
       def find_milestone(project_ref, namespace_ref, milestone_id, milestone_name)
         project_path = full_project_path(namespace_ref, project_ref)
-        project = project_from_ref(project_path)
+        project = parent_from_ref(project_path)
 
         return unless project
 
diff --git a/lib/banzai/issuable_extractor.rb b/lib/banzai/issuable_extractor.rb
index cbabf9156de..49603d0b363 100644
--- a/lib/banzai/issuable_extractor.rb
+++ b/lib/banzai/issuable_extractor.rb
@@ -28,8 +28,8 @@ module Banzai
       issue_parser = Banzai::ReferenceParser::IssueParser.new(project, user)
       merge_request_parser = Banzai::ReferenceParser::MergeRequestParser.new(project, user)
 
-      issuables_for_nodes = issue_parser.issues_for_nodes(nodes).merge(
-        merge_request_parser.merge_requests_for_nodes(nodes)
+      issuables_for_nodes = issue_parser.records_for_nodes(nodes).merge(
+        merge_request_parser.records_for_nodes(nodes)
       )
 
       # The project for the issue/MR might be pending for deletion!
diff --git a/lib/banzai/reference_parser/epic_parser.rb b/lib/banzai/reference_parser/epic_parser.rb
new file mode 100644
index 00000000000..08b8a4c9a0f
--- /dev/null
+++ b/lib/banzai/reference_parser/epic_parser.rb
@@ -0,0 +1,12 @@
+module Banzai
+  module ReferenceParser
+    # The actual parser is implemented in the EE mixin
+    class EpicParser < IssuableParser
+      self.reference_type = :epic
+
+      def records_for_nodes(_nodes)
+        {}
+      end
+    end
+  end
+end
diff --git a/lib/banzai/reference_parser/issuable_parser.rb b/lib/banzai/reference_parser/issuable_parser.rb
new file mode 100644
index 00000000000..3953867eb83
--- /dev/null
+++ b/lib/banzai/reference_parser/issuable_parser.rb
@@ -0,0 +1,25 @@
+module Banzai
+  module ReferenceParser
+    class IssuableParser < BaseParser
+      def nodes_visible_to_user(user, nodes)
+        records = records_for_nodes(nodes)
+
+        nodes.select do |node|
+          issuable = records[node]
+
+          issuable && can_read_reference?(user, issuable)
+        end
+      end
+
+      def referenced_by(nodes)
+        records = records_for_nodes(nodes)
+
+        nodes.map { |node| records[node] }.compact.uniq
+      end
+
+      def can_read_reference?(user, issuable)
+        can?(user, "read_#{issuable.class.to_s.underscore}".to_sym, issuable)
+      end
+    end
+  end
+end
diff --git a/lib/banzai/reference_parser/issue_parser.rb b/lib/banzai/reference_parser/issue_parser.rb
index e0a8ca653cb..38d4e3f3e44 100644
--- a/lib/banzai/reference_parser/issue_parser.rb
+++ b/lib/banzai/reference_parser/issue_parser.rb
@@ -1,10 +1,10 @@
 module Banzai
   module ReferenceParser
-    class IssueParser < BaseParser
+    class IssueParser < IssuableParser
       self.reference_type = :issue
 
       def nodes_visible_to_user(user, nodes)
-        issues = issues_for_nodes(nodes)
+        issues = records_for_nodes(nodes)
 
         readable_issues = Ability
           .issues_readable_by_user(issues.values, user).to_set
@@ -14,13 +14,7 @@ module Banzai
         end
       end
 
-      def referenced_by(nodes)
-        issues = issues_for_nodes(nodes)
-
-        nodes.map { |node| issues[node] }.compact.uniq
-      end
-
-      def issues_for_nodes(nodes)
+      def records_for_nodes(nodes)
         @issues_for_nodes ||= grouped_objects_for_nodes(
           nodes,
           Issue.all.includes(
diff --git a/lib/banzai/reference_parser/merge_request_parser.rb b/lib/banzai/reference_parser/merge_request_parser.rb
index 75cbc7fdac4..a370ff5b5b3 100644
--- a/lib/banzai/reference_parser/merge_request_parser.rb
+++ b/lib/banzai/reference_parser/merge_request_parser.rb
@@ -1,25 +1,9 @@
 module Banzai
   module ReferenceParser
-    class MergeRequestParser < BaseParser
+    class MergeRequestParser < IssuableParser
       self.reference_type = :merge_request
 
-      def nodes_visible_to_user(user, nodes)
-        merge_requests = merge_requests_for_nodes(nodes)
-
-        nodes.select do |node|
-          merge_request = merge_requests[node]
-
-          merge_request && can?(user, :read_merge_request, merge_request.project)
-        end
-      end
-
-      def referenced_by(nodes)
-        merge_requests = merge_requests_for_nodes(nodes)
-
-        nodes.map { |node| merge_requests[node] }.compact.uniq
-      end
-
-      def merge_requests_for_nodes(nodes)
+      def records_for_nodes(nodes)
         @merge_requests_for_nodes ||= grouped_objects_for_nodes(
           nodes,
           MergeRequest.includes(
@@ -40,10 +24,6 @@ module Banzai
           self.class.data_attribute
         )
       end
-
-      def can_read_reference?(user, ref_project, node)
-        can?(user, :read_merge_request, ref_project)
-      end
     end
   end
 end
diff --git a/lib/gitlab/reference_extractor.rb b/lib/gitlab/reference_extractor.rb
index bc836dcc08d..9ff82d628c0 100644
--- a/lib/gitlab/reference_extractor.rb
+++ b/lib/gitlab/reference_extractor.rb
@@ -1,7 +1,7 @@
 module Gitlab
   # Extract possible GFM references from an arbitrary String for further processing.
   class ReferenceExtractor < Banzai::ReferenceExtractor
-    REFERABLES = %i(user issue label milestone merge_request snippet commit commit_range directly_addressed_user).freeze
+    REFERABLES = %i(user issue label milestone merge_request snippet commit commit_range directly_addressed_user epic).freeze
     attr_accessor :project, :current_user, :author
 
     def initialize(project, current_user = nil)
diff --git a/spec/features/markdown_spec.rb b/spec/features/markdown_spec.rb
index cc1b187ff54..e285befc66f 100644
--- a/spec/features/markdown_spec.rb
+++ b/spec/features/markdown_spec.rb
@@ -207,8 +207,9 @@ describe 'GitLab Markdown' do
   before do
     @feat = MarkdownFeature.new
 
-    # `markdown` helper expects a `@project` variable
+    # `markdown` helper expects a `@project` and `@group` variable
     @project = @feat.project
+    @group = @feat.group
   end
 
   context 'default pipeline' do
diff --git a/spec/lib/banzai/cross_project_reference_spec.rb b/spec/lib/banzai/cross_project_reference_spec.rb
index d70749536b8..68ca960caab 100644
--- a/spec/lib/banzai/cross_project_reference_spec.rb
+++ b/spec/lib/banzai/cross_project_reference_spec.rb
@@ -3,20 +3,20 @@ require 'spec_helper'
 describe Banzai::CrossProjectReference do
   include described_class
 
-  describe '#project_from_ref' do
+  describe '#parent_from_ref' do
     context 'when no project was referenced' do
       it 'returns the project from context' do
         project = double
 
         allow(self).to receive(:context).and_return({ project: project })
 
-        expect(project_from_ref(nil)).to eq project
+        expect(parent_from_ref(nil)).to eq project
       end
     end
 
     context 'when referenced project does not exist' do
       it 'returns nil' do
-        expect(project_from_ref('invalid/reference')).to be_nil
+        expect(parent_from_ref('invalid/reference')).to be_nil
       end
     end
 
@@ -27,7 +27,7 @@ describe Banzai::CrossProjectReference do
         expect(Project).to receive(:find_by_full_path)
           .with('cross/reference').and_return(project2)
 
-        expect(project_from_ref('cross/reference')).to eq project2
+        expect(parent_from_ref('cross/reference')).to eq project2
       end
     end
   end
diff --git a/spec/lib/banzai/filter/abstract_reference_filter_spec.rb b/spec/lib/banzai/filter/abstract_reference_filter_spec.rb
index 7c0ba9ee67f..1e82d18d056 100644
--- a/spec/lib/banzai/filter/abstract_reference_filter_spec.rb
+++ b/spec/lib/banzai/filter/abstract_reference_filter_spec.rb
@@ -3,67 +3,67 @@ require 'spec_helper'
 describe Banzai::Filter::AbstractReferenceFilter do
   let(:project) { create(:project) }
 
-  describe '#references_per_project' do
-    it 'returns a Hash containing references grouped per project paths' do
+  describe '#references_per_parent' do
+    it 'returns a Hash containing references grouped per parent paths' do
       doc = Nokogiri::HTML.fragment("#1 #{project.full_path}#2")
       filter = described_class.new(doc, project: project)
 
       expect(filter).to receive(:object_class).exactly(4).times.and_return(Issue)
       expect(filter).to receive(:object_sym).twice.and_return(:issue)
 
-      refs = filter.references_per_project
+      refs = filter.references_per_parent
 
       expect(refs).to be_an_instance_of(Hash)
       expect(refs[project.full_path]).to eq(Set.new(%w[1 2]))
     end
   end
 
-  describe '#projects_per_reference' do
-    it 'returns a Hash containing projects grouped per project paths' do
+  describe '#parent_per_reference' do
+    it 'returns a Hash containing projects grouped per parent paths' do
       doc = Nokogiri::HTML.fragment('')
       filter = described_class.new(doc, project: project)
 
-      expect(filter).to receive(:references_per_project)
+      expect(filter).to receive(:references_per_parent)
         .and_return({ project.full_path => Set.new(%w[1]) })
 
-      expect(filter.projects_per_reference)
+      expect(filter.parent_per_reference)
         .to eq({ project.full_path => project })
     end
   end
 
-  describe '#find_projects_for_paths' do
+  describe '#find_for_paths' do
     let(:doc) { Nokogiri::HTML.fragment('') }
     let(:filter) { described_class.new(doc, project: project) }
 
     context 'with RequestStore disabled' do
       it 'returns a list of Projects for a list of paths' do
-        expect(filter.find_projects_for_paths([project.full_path]))
+        expect(filter.find_for_paths([project.full_path]))
           .to eq([project])
       end
 
       it "return an empty array for paths that don't exist" do
-        expect(filter.find_projects_for_paths(['nonexistent/project']))
+        expect(filter.find_for_paths(['nonexistent/project']))
           .to eq([])
       end
     end
 
     context 'with RequestStore enabled', :request_store do
       it 'returns a list of Projects for a list of paths' do
-        expect(filter.find_projects_for_paths([project.full_path]))
+        expect(filter.find_for_paths([project.full_path]))
           .to eq([project])
       end
 
       context "when no project with that path exists" do
         it "returns no value" do
-          expect(filter.find_projects_for_paths(['nonexistent/project']))
+          expect(filter.find_for_paths(['nonexistent/project']))
             .to eq([])
         end
 
         it "adds the ref to the project refs cache" do
           project_refs_cache = {}
-          allow(filter).to receive(:project_refs_cache).and_return(project_refs_cache)
+          allow(filter).to receive(:refs_cache).and_return(project_refs_cache)
 
-          filter.find_projects_for_paths(['nonexistent/project'])
+          filter.find_for_paths(['nonexistent/project'])
 
           expect(project_refs_cache).to eq({ 'nonexistent/project' => nil })
         end
@@ -71,11 +71,11 @@ describe Banzai::Filter::AbstractReferenceFilter do
         context 'when the project refs cache includes nil values' do
           before do
             # adds { 'nonexistent/project' => nil } to cache
-            filter.project_from_ref_cached('nonexistent/project')
+            filter.from_ref_cached('nonexistent/project')
           end
 
           it "return an empty array for paths that don't exist" do
-            expect(filter.find_projects_for_paths(['nonexistent/project']))
+            expect(filter.find_for_paths(['nonexistent/project']))
               .to eq([])
           end
         end
@@ -83,12 +83,12 @@ describe Banzai::Filter::AbstractReferenceFilter do
     end
   end
 
-  describe '#current_project_path' do
-    it 'returns the path of the current project' do
+  describe '#current_parent_path' do
+    it 'returns the path of the current parent' do
       doc = Nokogiri::HTML.fragment('')
       filter = described_class.new(doc, project: project)
 
-      expect(filter.current_project_path).to eq(project.full_path)
+      expect(filter.current_parent_path).to eq(project.full_path)
     end
   end
 end
diff --git a/spec/lib/banzai/filter/issue_reference_filter_spec.rb b/spec/lib/banzai/filter/issue_reference_filter_spec.rb
index f70c69ef588..3a5f52ea23f 100644
--- a/spec/lib/banzai/filter/issue_reference_filter_spec.rb
+++ b/spec/lib/banzai/filter/issue_reference_filter_spec.rb
@@ -157,6 +157,12 @@ describe Banzai::Filter::IssueReferenceFilter do
       expect(doc.text).to eq("Fixed (#{project2.full_path}##{issue.iid}.)")
     end
 
+    it 'includes default classes' do
+      doc = reference_filter("Fixed (#{reference}.)")
+
+      expect(doc.css('a').first.attr('class')).to eq 'gfm gfm-issue has-tooltip'
+    end
+
     it 'ignores invalid issue IDs on the referenced project' do
       exp = act = "Fixed #{invalidate_reference(reference)}"
 
@@ -201,6 +207,12 @@ describe Banzai::Filter::IssueReferenceFilter do
       expect(doc.text).to eq("Fixed (#{project2.path}##{issue.iid}.)")
     end
 
+    it 'includes default classes' do
+      doc = reference_filter("Fixed (#{reference}.)")
+
+      expect(doc.css('a').first.attr('class')).to eq 'gfm gfm-issue has-tooltip'
+    end
+
     it 'ignores invalid issue IDs on the referenced project' do
       exp = act = "Fixed #{invalidate_reference(reference)}"
 
@@ -245,6 +257,12 @@ describe Banzai::Filter::IssueReferenceFilter do
       expect(doc.text).to eq("Fixed (#{project2.path}##{issue.iid}.)")
     end
 
+    it 'includes default classes' do
+      doc = reference_filter("Fixed (#{reference}.)")
+
+      expect(doc.css('a').first.attr('class')).to eq 'gfm gfm-issue has-tooltip'
+    end
+
     it 'ignores invalid issue IDs on the referenced project' do
       exp = act = "Fixed #{invalidate_reference(reference)}"
 
@@ -269,8 +287,15 @@ describe Banzai::Filter::IssueReferenceFilter do
 
     it 'links with adjacent text' do
       doc = reference_filter("Fixed (#{reference}.)")
+
       expect(doc.to_html).to match(/\(<a.+>#{Regexp.escape(issue.to_reference(project))} \(comment 123\)<\/a>\.\)/)
     end
+
+    it 'includes default classes' do
+      doc = reference_filter("Fixed (#{reference}.)")
+
+      expect(doc.css('a').first.attr('class')).to eq 'gfm gfm-issue has-tooltip'
+    end
   end
 
   context 'cross-project reference in link href' do
@@ -291,8 +316,15 @@ describe Banzai::Filter::IssueReferenceFilter do
 
     it 'links with adjacent text' do
       doc = reference_filter("Fixed (#{reference_link}.)")
+
       expect(doc.to_html).to match(/\(<a.+>Reference<\/a>\.\)/)
     end
+
+    it 'includes default classes' do
+      doc = reference_filter("Fixed (#{reference_link}.)")
+
+      expect(doc.css('a').first.attr('class')).to eq 'gfm gfm-issue has-tooltip'
+    end
   end
 
   context 'cross-project URL in link href' do
@@ -313,8 +345,15 @@ describe Banzai::Filter::IssueReferenceFilter do
 
     it 'links with adjacent text' do
       doc = reference_filter("Fixed (#{reference_link}.)")
+
       expect(doc.to_html).to match(/\(<a.+>Reference<\/a>\.\)/)
     end
+
+    it 'includes default classes' do
+      doc = reference_filter("Fixed (#{reference_link}.)")
+
+      expect(doc.css('a').first.attr('class')).to eq 'gfm gfm-issue has-tooltip'
+    end
   end
 
   context 'group context' do
@@ -387,19 +426,19 @@ describe Banzai::Filter::IssueReferenceFilter do
     end
   end
 
-  describe '#issues_per_project' do
+  describe '#records_per_parent' do
     context 'using an internal issue tracker' do
       it 'returns a Hash containing the issues per project' do
         doc = Nokogiri::HTML.fragment('')
         filter = described_class.new(doc, project: project)
 
-        expect(filter).to receive(:projects_per_reference)
+        expect(filter).to receive(:parent_per_reference)
           .and_return({ project.full_path => project })
 
-        expect(filter).to receive(:references_per_project)
+        expect(filter).to receive(:references_per_parent)
           .and_return({ project.full_path => Set.new([issue.iid]) })
 
-        expect(filter.issues_per_project)
+        expect(filter.records_per_parent)
           .to eq({ project => { issue.iid => issue } })
       end
     end
diff --git a/spec/lib/banzai/reference_parser/issue_parser_spec.rb b/spec/lib/banzai/reference_parser/issue_parser_spec.rb
index 23dbe2b6238..4cef3bdb24b 100644
--- a/spec/lib/banzai/reference_parser/issue_parser_spec.rb
+++ b/spec/lib/banzai/reference_parser/issue_parser_spec.rb
@@ -70,12 +70,12 @@ describe Banzai::ReferenceParser::IssueParser do
     end
   end
 
-  describe '#issues_for_nodes' do
+  describe '#records_for_nodes' do
     it 'returns a Hash containing the issues for a list of nodes' do
       link['data-issue'] = issue.id.to_s
       nodes = [link]
 
-      expect(subject.issues_for_nodes(nodes)).to eq({ link => issue })
+      expect(subject.records_for_nodes(nodes)).to eq({ link => issue })
     end
   end
 end
diff --git a/spec/lib/gitlab/reference_extractor_spec.rb b/spec/lib/gitlab/reference_extractor_spec.rb
index 476a3f1998d..ef874368077 100644
--- a/spec/lib/gitlab/reference_extractor_spec.rb
+++ b/spec/lib/gitlab/reference_extractor_spec.rb
@@ -250,4 +250,34 @@ describe Gitlab::ReferenceExtractor do
     subject { described_class.references_pattern }
     it { is_expected.to be_kind_of Regexp }
   end
+
+  describe 'referables prefixes' do
+    def prefixes
+      described_class::REFERABLES.each_with_object({}) do |referable, result|
+        klass = referable.to_s.camelize.constantize
+
+        next unless klass.respond_to?(:reference_prefix)
+
+        prefix = klass.reference_prefix
+        result[prefix] ||= []
+        result[prefix] << referable
+      end
+    end
+
+    it 'returns all supported prefixes' do
+      expect(prefixes.keys.uniq).to match_array(%w(@ # ~ % ! $ &))
+    end
+
+    it 'does not allow one prefix for multiple referables if not allowed specificly' do
+      # make sure you are not overriding existing prefix before changing this hash
+      multiple_allowed = {
+        '@' => 3
+      }
+
+      prefixes.each do |prefix, referables|
+        expected_count = multiple_allowed[prefix] || 1
+        expect(referables.count).to eq(expected_count)
+      end
+    end
+  end
 end