Split Markdown rendering & reference gathering

This splits the Markdown rendering and reference extraction phases into
two distinct code bases. The reference extraction phase no longer relies
on the html-pipeline Gem (and any related code) and allows for
extracting of references from multiple HTML nodes in a single pass. This
means that if you want to extract user references from 200 comments you
no longer need to run 200 times N number of queries, instead only a
handful of queries may be needed.

app/controllers/projects/wikis_controller.rb

@@ -91,8 +91,8 @@ class Projects::WikisController < Projects::ApplicationController
   def markdown_preview
     text = params[:text]
 
-    ext = Gitlab::ReferenceExtractor.new(@project, current_user, current_user)
-    ext.analyze(text)
+    ext = Gitlab::ReferenceExtractor.new(@project, current_user)
+    ext.analyze(text, author: current_user)
 
     render json: {
       body: view_context.markdown(text, pipeline: :wiki, project_wiki: @project_wiki),

app/controllers/projects_controller.rb

@@ -197,8 +197,8 @@ class ProjectsController < Projects::ApplicationController
   def markdown_preview
     text = params[:text]
 
-    ext = Gitlab::ReferenceExtractor.new(@project, current_user, current_user)
-    ext.analyze(text)
+    ext = Gitlab::ReferenceExtractor.new(@project, current_user)
+    ext.analyze(text, author: current_user)
 
     render json: {
       body:       view_context.markdown(text),

lib/banzai/filter/abstract_reference_filter.rb

@@ -18,10 +18,6 @@ module Banzai
         @object_sym ||= object_name.to_sym
       end
 
-      def self.data_reference
-        @data_reference ||= "data-#{object_name.dasherize}"
-      end
-
       def self.object_class_title
         @object_title ||= object_class.name.titleize
       end
@@ -45,10 +41,6 @@ module Banzai
         end
       end
 
-      def self.referenced_by(node)
-        { object_sym => LazyReference.new(object_class, node.attr(data_reference)) }
-      end
-
       def object_class
         self.class.object_class
       end

lib/banzai/filter/commit_range_reference_filter.rb

@@ -4,6 +4,8 @@ module Banzai
     #
     # This filter supports cross-project references.
     class CommitRangeReferenceFilter < AbstractReferenceFilter
+      self.reference_type = :commit_range
+
       def self.object_class
         CommitRange
       end
@@ -14,34 +16,18 @@ module Banzai
         end
       end
 
-      def self.referenced_by(node)
-        project = Project.find(node.attr("data-project")) rescue nil
-        return unless project
-
-        id = node.attr("data-commit-range")
-        range = find_object(project, id)
-
-        return unless range
-
-        { commit_range: range }
-      end
-
       def initialize(*args)
         super
 
         @commit_map = {}
       end
 
-      def self.find_object(project, id)
+      def find_object(project, id)
         range = CommitRange.new(id, project)
 
         range.valid_commits? ? range : nil
       end
 
-      def find_object(*args)
-        self.class.find_object(*args)
-      end
-
       def url_for_object(range, project)
         h = Gitlab::Routing.url_helpers
         h.namespace_project_compare_url(project.namespace, project,

lib/banzai/filter/commit_reference_filter.rb

@@ -4,6 +4,8 @@ module Banzai
     #
     # This filter supports cross-project references.
     class CommitReferenceFilter < AbstractReferenceFilter
+      self.reference_type = :commit
+
       def self.object_class
         Commit
       end
@@ -14,28 +16,12 @@ module Banzai
         end
       end
 
-      def self.referenced_by(node)
-        project = Project.find(node.attr("data-project")) rescue nil
-        return unless project
-
-        id = node.attr("data-commit")
-        commit = find_object(project, id)
-
-        return unless commit
-
-        { commit: commit }
-      end
-
-      def self.find_object(project, id)
+      def find_object(project, id)
         if project && project.valid_repo?
           project.commit(id)
         end
       end
 
-      def find_object(*args)
-        self.class.find_object(*args)
-      end
-
       def url_for_object(commit, project)
         h = Gitlab::Routing.url_helpers
         h.namespace_project_commit_url(project.namespace, project, commit,

lib/banzai/filter/external_issue_reference_filter.rb

@@ -4,6 +4,8 @@ module Banzai
     # References are ignored if the project doesn't use an external issue
     # tracker.
     class ExternalIssueReferenceFilter < ReferenceFilter
+      self.reference_type = :external_issue
+
       # Public: Find `JIRA-123` issue references in text
       #
       #   ExternalIssueReferenceFilter.references_in(text) do |match, issue|
@@ -21,18 +23,6 @@ module Banzai
         end
       end
 
-      def self.referenced_by(node)
-        project = Project.find(node.attr("data-project")) rescue nil
-        return unless project
-
-        id = node.attr("data-external-issue")
-        external_issue = ExternalIssue.new(id, project)
-
-        return unless external_issue
-
-        { external_issue: external_issue }
-      end
-
       def call
         # Early return if the project isn't using an external tracker
         return doc if project.nil? || default_issues_tracker?

lib/banzai/filter/issue_reference_filter.rb

@@ -5,18 +5,12 @@ module Banzai
     #
     # This filter supports cross-project references.
     class IssueReferenceFilter < AbstractReferenceFilter
+      self.reference_type = :issue
+
       def self.object_class
         Issue
       end
 
-      def self.user_can_see_reference?(user, node, context)
-        # It is not possible to check access rights for external issue trackers
-        return true if context[:project].try(:external_issue_tracker)
- 
-        issue = Issue.find(node.attr('data-issue')) rescue nil
-        Ability.abilities.allowed?(user, :read_issue, issue)
-      end
-
       def find_object(project, id)
         project.get_issue(id)
       end

lib/banzai/filter/label_reference_filter.rb

@@ -2,6 +2,8 @@ module Banzai
   module Filter
     # HTML filter that replaces label references with links.
     class LabelReferenceFilter < AbstractReferenceFilter
+      self.reference_type = :label
+
       def self.object_class
         Label
       end

lib/banzai/filter/merge_request_reference_filter.rb

@@ -5,6 +5,8 @@ module Banzai
     #
     # This filter supports cross-project references.
     class MergeRequestReferenceFilter < AbstractReferenceFilter
+      self.reference_type = :merge_request
+
       def self.object_class
         MergeRequest
       end

lib/banzai/filter/milestone_reference_filter.rb

@@ -2,6 +2,8 @@ module Banzai
   module Filter
     # HTML filter that replaces milestone references with links.
     class MilestoneReferenceFilter < AbstractReferenceFilter
+      self.reference_type = :milestone
+
       def self.object_class
         Milestone
       end

lib/banzai/filter/redactor_filter.rb

@@ -7,8 +7,11 @@ module Banzai
     #
     class RedactorFilter < HTML::Pipeline::Filter
       def call
-        Querying.css(doc, 'a.gfm').each do |node|
-          unless user_can_see_reference?(node)
+        nodes = Querying.css(doc, 'a.gfm[data-reference-type]')
+        visible = nodes_visible_to_user(nodes)
+
+        nodes.each do |node|
+          unless visible.include?(node)
             # The reference should be replaced by the original text,
             # which is not always the same as the rendered text.
             text = node.attr('data-original') || node.text
@@ -21,20 +24,30 @@ module Banzai
 
       private
 
-      def user_can_see_reference?(node)
-        if node.has_attribute?('data-reference-filter')
-          reference_type = node.attr('data-reference-filter')
-          reference_filter = Banzai::Filter.const_get(reference_type)
+      def nodes_visible_to_user(nodes)
+        per_type = Hash.new { |h, k| h[k] = [] }
+        visible = Set.new
+
+        nodes.each do |node|
+          per_type[node.attr('data-reference-type')] << node
+        end
+
+        per_type.each do |type, nodes|
+          parser = Banzai::ReferenceParser[type].new(project, current_user)
 
-          reference_filter.user_can_see_reference?(current_user, node, context)
-        else
-          true
+          visible.merge(parser.nodes_visible_to_user(current_user, nodes))
         end
+
+        visible
       end
 
       def current_user
         context[:current_user]
       end
+
+      def project
+        context[:project]
+      end
     end
   end
 end

lib/banzai/filter/reference_filter.rb

@@ -8,24 +8,8 @@ module Banzai
     #   :project (required) - Current project, ignored if reference is cross-project.
     #   :only_path          - Generate path-only links.
     class ReferenceFilter < HTML::Pipeline::Filter
-      def self.user_can_see_reference?(user, node, context)
-        if node.has_attribute?('data-project')
-          project_id = node.attr('data-project').to_i
-          return true if project_id == context[:project].try(:id)
-
-          project = Project.find(project_id) rescue nil
-          Ability.abilities.allowed?(user, :read_project, project)
-        else
-          true
-        end
-      end
-
-      def self.user_can_reference?(user, node, context)
-        true
-      end
-
-      def self.referenced_by(node)
-        raise NotImplementedError, "#{self} does not implement #{__method__}"
+      class << self
+        attr_accessor :reference_type
       end
 
       # Returns a data attribute String to attach to a reference link
@@ -43,7 +27,9 @@ module Banzai
       #
       # Returns a String
       def data_attribute(attributes = {})
-        attributes[:reference_filter] = self.class.name.demodulize
+        attributes = attributes.reject { |_, v| v.nil? }
+
+        attributes[:reference_type] = self.class.reference_type
         attributes.delete(:original) if context[:no_original_data]
         attributes.map { |key, value| %Q(data-#{key.to_s.dasherize}="#{escape_once(value)}") }.join(" ")
       end

lib/banzai/filter/reference_gatherer_filter.rb

-module Banzai
-  module Filter
-    # HTML filter that gathers all referenced records that the current user has
-    # permission to view.
-    #
-    # Expected to be run in its own post-processing pipeline.
-    #
-    class ReferenceGathererFilter < HTML::Pipeline::Filter
-      def initialize(*)
-        super
-
-        result[:references] ||= Hash.new { |hash, type| hash[type] = [] }
-      end
-
-      def call
-        Querying.css(doc, 'a.gfm').each do |node|
-          gather_references(node)
-        end
-
-        load_lazy_references unless ReferenceExtractor.lazy?
-
-        doc
-      end
-
-      private
-
-      def gather_references(node)
-        return unless node.has_attribute?('data-reference-filter')
-
-        reference_type = node.attr('data-reference-filter')
-        reference_filter = Banzai::Filter.const_get(reference_type)
-
-        return if context[:reference_filter] && reference_filter != context[:reference_filter]
-
-        return if author && !reference_filter.user_can_reference?(author, node, context)
-
-        return unless reference_filter.user_can_see_reference?(current_user, node, context)
-
-        references = reference_filter.referenced_by(node)
-        return unless references
-
-        references.each do |type, values|
-          Array.wrap(values).each do |value|
-            result[:references][type] << value
-          end
-        end
-      end
-
-      def load_lazy_references
-        refs = result[:references]
-        refs.each do |type, values|
-          refs[type] = ReferenceExtractor.lazily(values)
-        end
-      end
-
-      def current_user
-        context[:current_user]
-      end
-
-      def author
-        context[:author]
-      end
-    end
-  end
-end

lib/banzai/filter/snippet_reference_filter.rb

@@ -5,6 +5,8 @@ module Banzai
     #
     # This filter supports cross-project references.
     class SnippetReferenceFilter < AbstractReferenceFilter
+      self.reference_type = :snippet
+
       def self.object_class
         Snippet
       end

lib/banzai/filter/user_reference_filter.rb

@@ -4,6 +4,8 @@ module Banzai
     #
     # A special `@all` reference is also supported.
     class UserReferenceFilter < ReferenceFilter
+      self.reference_type = :user
+
       # Public: Find `@user` user references in text
       #
       #   UserReferenceFilter.references_in(text) do |match, username|
@@ -21,43 +23,6 @@ module Banzai
         end
       end
 
-      def self.referenced_by(node)
-        if node.has_attribute?('data-group')
-          group = Group.find(node.attr('data-group')) rescue nil
-          return unless group
-
-          { user: group.users }
-        elsif node.has_attribute?('data-user')
-          { user: LazyReference.new(User, node.attr('data-user')) }
-        elsif node.has_attribute?('data-project')
-          project = Project.find(node.attr('data-project')) rescue nil
-          return unless project
-
-          { user: project.team.members.flatten }
-        end
-      end
-
-      def self.user_can_see_reference?(user, node, context)
-        if node.has_attribute?('data-group')
-          group = Group.find(node.attr('data-group')) rescue nil
-          Ability.abilities.allowed?(user, :read_group, group)
-        else
-          super
-        end
-      end
-
-      def self.user_can_reference?(user, node, context)
-        # Only team members can reference `@all`
-        if node.has_attribute?('data-project')
-          project = Project.find(node.attr('data-project')) rescue nil
-          return false unless project
-
-          user && project.team.member?(user)
-        else
-          super
-        end
-      end
-
       def call
         return doc if project.nil?
 
@@ -114,9 +79,12 @@ module Banzai
 
       def link_to_all(link_text: nil)
         project = context[:project]
+        author = context[:author]
+
         url = urls.namespace_project_url(project.namespace, project,
                                          only_path: context[:only_path])
-        data = data_attribute(project: project.id)
+
+        data = data_attribute(project: project.id, author: author.try(:id))
         text = link_text || User.reference_prefix + 'all'
 
         link_tag(url, data, text)

lib/banzai/lazy_reference.rb

-module Banzai
-  class LazyReference
-    def self.load(refs)
-      lazy_references, values = refs.partition { |ref| ref.is_a?(self) }
-
-      lazy_values = lazy_references.group_by(&:klass).flat_map do |klass, refs|
-        ids = refs.flat_map(&:ids)
-        klass.where(id: ids)
-      end
-
-      values + lazy_values
-    end
-
-    attr_reader :klass, :ids
-
-    def initialize(klass, ids)
-      @klass = klass
-      @ids = Array.wrap(ids).map(&:to_i)
-    end
-
-    def load
-      self.klass.where(id: self.ids)
-    end
-  end
-end

lib/banzai/pipeline/reference_extraction_pipeline.rb

-module Banzai
-  module Pipeline
-    class ReferenceExtractionPipeline < BasePipeline
-      def self.filters
-        FilterArray[
-          Filter::ReferenceGathererFilter
-        ]
-      end
-    end
-  end
-end

lib/banzai/reference_extractor.rb

 module Banzai
   # Extract possible GFM references from an arbitrary String for further processing.
   class ReferenceExtractor
-    class << self
-      LAZY_KEY = :banzai_reference_extractor_lazy
-
-      def lazy?
-        Thread.current[LAZY_KEY]
-      end
-
-      def lazily(values = nil, &block)
-        return (values || block.call).uniq if lazy?
-
-        begin
-          Thread.current[LAZY_KEY] = true
-
-          values ||= block.call
-
-          Banzai::LazyReference.load(values.uniq).uniq
-        ensure
-          Thread.current[LAZY_KEY] = false
-        end
-      end
-    end
-
     def initialize
       @texts = []
     end
@@ -31,23 +9,21 @@ module Banzai
       @texts << Renderer.render(text, context)
     end
 
-    def references(type, context = {})
-      filter = Banzai::Filter["#{type}_reference"]
+    def references(type, project, current_user = nil)
+      processor = Banzai::ReferenceParser[type].
+        new(project, current_user)
+
+      processor.process(html_documents)
+    end
 
-      context.merge!(
-        pipeline: :reference_extraction,
+    private
 
-        # ReferenceGathererFilter
-        reference_filter: filter
-      )
+    def html_documents
+      # This ensures that we don't memoize anything until we have a number of
+      # text blobs to parse.
+      return [] if @texts.empty?
 
-      self.class.lazily do
-        @texts.flat_map do |html|
-          text_context = context.dup
-          result = Renderer.render_result(html, text_context)
-          result[:references][type]
-        end.uniq
-      end
+      @html_documents ||= @texts.map { |html| Nokogiri::HTML.fragment(html) }
     end
   end
 end

lib/banzai/reference_parser.rb

+module Banzai
+  module ReferenceParser
+    # Returns the reference parser class for the given type
+    #
+    # Example:
+    #
+    #     Banzai::ReferenceParser['issue']
+    #
+    # This would return the `Banzai::ReferenceParser::IssueParser` class.
+    def self.[](name)
+      const_get("#{name.to_s.camelize}Parser")
+    end
+  end
+end

lib/banzai/reference_parser/base_parser.rb

+module Banzai
+  module ReferenceParser
+    # Base class for reference parsing classes.
+    #
+    # Each parser should also specify its reference type by calling
+    # `self.reference_type = ...` in the body of the class. The value of this
+    # method should be a symbol such as `:issue` or `:merge_request`. For
+    # example:
+    #
+    #     class IssueParser < BaseParser
+    #       self.reference_type = :issue
+    #     end
+    #
+    # The reference type is used to determine what nodes to pass to the
+    # `referenced_by` method.
+    #
+    # Parser classes should either implement the instance method
+    # `references_relation` or overwrite `referenced_by`. The
+    # `references_relation` method is supposed to return an
+    # ActiveRecord::Relation used as a base relation for retrieving the objects
+    # referenced in a set of HTML nodes.
+    #
+    # Each class can implement two additional methods:
+    #
+    # * `nodes_user_can_reference`: returns an Array of nodes the given user can
+    #   refer to.
+    # * `nodes_visible_to_user`: returns an Array of nodes that are visible to
+    #   the given user.
+    #
+    # You only need to overwrite these methods if you want to tweak who can see
+    # which references. For example, the IssueParser class defines its own
+    # `nodes_visible_to_user` method so it can ensure users can only see issues
+    # they have access to.
+    class BaseParser
+      class << self
+        attr_accessor :reference_type
+      end
+
+      # Returns the attribute name containing the value for every object to be
+      # parsed by the current parser.
+      #
+      # For example, for a parser class that returns "Animal" objects this
+      # attribute would be "data-animal".
+      def self.data_attribute
+        @data_attribute ||= "data-#{reference_type.to_s.dasherize}"
+      end
+
+      def initialize(project = nil, current_user = nil)
+        @project = project
+        @current_user = current_user
+      end
+
+      # Returns all the nodes containing references that the user can refer to.
+      def nodes_user_can_reference(user, nodes)
+        nodes
+      end
+
+      # Returns all the nodes that are visible to the given user.
+      def nodes_visible_to_user(user, nodes)
+        projects = lazy { projects_for_nodes(nodes) }
+        project_attr = 'data-project'
+
+        nodes.select do |node|
+          if node.has_attribute?(project_attr)
+            node_id = node.attr(project_attr).to_i
+
+            if project && project.id == node_id
+              true
+            else
+              can?(user, :read_project, projects[node_id])
+            end
+          else
+            true
+          end
+        end
+      end
+
+      # Returns an Array of objects referenced by any of the given HTML nodes.
+      def referenced_by(nodes)
+        ids = unique_attribute_values(nodes, self.class.data_attribute)
+
+        references_relation.where(id: ids)
+      end
+
+      # Returns the ActiveRecord::Relation to use for querying references in the
+      # DB.
+      def references_relation
+        raise NotImplementedError,
+          "#{self.class} does not implement #{__method__}"
+      end
+
+      # Returns a Hash containing attribute values per project ID.
+      #
+      # The returned Hash uses the following format:
+      #
+      #     { project id => [value1, value2, ...] }
+      #
+      # nodes - An Array of HTML nodes to process.
+      # attribute - The name of the attribute (as a String) for which to gather
+      #             values.
+      #
+      # Returns a Hash.
+      def gather_attributes_per_project(nodes, attribute)
+        per_project = Hash.new { |hash, key| hash[key] = Set.new }
+
+        nodes.each do |node|
+          project_id = node.attr('data-project').to_i
+          id = node.attr(attribute)
+
+          per_project[project_id] << id if id
+        end
+
+        per_project
+      end
+
+      # Returns a Hash containing objects for an attribute grouped per their
+      # IDs.
+      #
+      # The returned Hash uses the following format:
+      #
+      #     { id value => row }
+      #
+      # nodes - An Array of HTML nodes to process.
+      #
+      # collection - The model or ActiveRecord relation to use for retrieving
+      #              rows from the database.
+      #
+      # attribute - The name of the attribute containing the primary key values
+      #             for every row.
+      #
+      # Returns a Hash.
+      def grouped_objects_for_nodes(nodes, collection, attribute)
+        return {} if nodes.empty?
+
+        ids = unique_attribute_values(nodes, attribute)
+
+        collection.where(id: ids).each_with_object({}) do |row, hash|
+          hash[row.id] = row
+        end
+      end
+
+      # Returns an Array containing all unique values of an attribute of the
+      # given nodes.
+      def unique_attribute_values(nodes, attribute)
+        values = Set.new
+
+        nodes.each do |node|
+          if node.has_attribute?(attribute)
+            values << node.attr(attribute)
+          end
+        end
+
+        values.to_a
+      end
+
+      # Processes the list of HTML documents and returns an Array containing all
+      # the references.
+      def process(documents)
+        type = self.class.reference_type
+
+        nodes = documents.flat_map do |document|
+          Querying.css(document, "a[data-reference-type='#{type}'].gfm").to_a
+        end
+
+        gather_references(nodes)
+      end
+
+      # Gathers the references for the given HTML nodes.
+      def gather_references(nodes)
+        nodes = nodes_user_can_reference(current_user, nodes)
+        nodes = nodes_visible_to_user(current_user, nodes)
+
+        referenced_by(nodes)
+      end
+
+      # Returns a Hash containing the projects for a given list of HTML nodes.
+      #
+      # The returned Hash uses the following format:
+      #
+      #     { project ID => project }
+      #
+      def projects_for_nodes(nodes)
+        @projects_for_nodes ||=
+          grouped_objects_for_nodes(nodes, Project, 'data-project')
+      end
+
+      def can?(user, permission, subject)
+        Ability.abilities.allowed?(user, permission, subject)
+      end
+
+      def find_projects_for_hash_keys(hash)
+        Project.where(id: hash.keys)
+      end
+
+      private
+
+      attr_reader :current_user, :project
+
+      def lazy(&block)
+        Gitlab::Lazy.new(&block)
+      end
+    end
+  end
+end

lib/banzai/reference_parser/commit_parser.rb

+module Banzai
+  module ReferenceParser
+    class CommitParser < BaseParser
+      self.reference_type = :commit
+
+      def referenced_by(nodes)
+        commit_ids = commit_ids_per_project(nodes)
+        projects = find_projects_for_hash_keys(commit_ids)
+
+        projects.flat_map do |project|
+          find_commits(project, commit_ids[project.id])
+        end
+      end
+
+      def commit_ids_per_project(nodes)
+        gather_attributes_per_project(nodes, self.class.data_attribute)
+      end
+
+      def find_commits(project, ids)
+        commits = []
+
+        return commits unless project.valid_repo?
+
+        ids.each do |id|
+          commit = project.commit(id)
+
+          commits << commit if commit
+        end
+
+        commits
+      end
+    end
+  end
+end

lib/banzai/reference_parser/commit_range_parser.rb

+module Banzai
+  module ReferenceParser
+    class CommitRangeParser < BaseParser
+      self.reference_type = :commit_range
+
+      def referenced_by(nodes)
+        range_ids = commit_range_ids_per_project(nodes)
+        projects = find_projects_for_hash_keys(range_ids)
+
+        projects.flat_map do |project|
+          find_ranges(project, range_ids[project.id])
+        end
+      end
+
+      def commit_range_ids_per_project(nodes)
+        gather_attributes_per_project(nodes, self.class.data_attribute)
+      end
+
+      def find_ranges(project, range_ids)
+        ranges = []
+
+        range_ids.each do |id|
+          range = find_object(project, id)
+
+          ranges << range if range
+        end
+
+        ranges
+      end
+
+      def find_object(project, id)
+        range = CommitRange.new(id, project)
+
+        range.valid_commits? ? range : nil
+      end
+    end
+  end
+end

lib/banzai/reference_parser/external_issue_parser.rb

+module Banzai
+  module ReferenceParser
+    class ExternalIssueParser < BaseParser
+      self.reference_type = :external_issue
+
+      def referenced_by(nodes)
+        issue_ids = issue_ids_per_project(nodes)
+        projects = find_projects_for_hash_keys(issue_ids)
+        issues = []
+
+        projects.each do |project|
+          issue_ids[project.id].each do |id|
+            issues << ExternalIssue.new(id, project)
+          end
+        end
+
+        issues
+      end
+
+      def issue_ids_per_project(nodes)
+        gather_attributes_per_project(nodes, self.class.data_attribute)
+      end
+    end
+  end
+end

lib/banzai/reference_parser/issue_parser.rb

+module Banzai
+  module ReferenceParser
+    class IssueParser < BaseParser
+      self.reference_type = :issue
+
+      def nodes_visible_to_user(user, nodes)
+        # It is not possible to check access rights for external issue trackers
+        return nodes if project && project.external_issue_tracker
+
+        issues = issues_for_nodes(nodes)
+
+        nodes.select do |node|
+          issue = issue_for_node(issues, node)
+
+          issue ? can?(user, :read_issue, issue) : false
+        end
+      end
+
+      def referenced_by(nodes)
+        issues = issues_for_nodes(nodes)
+
+        nodes.map { |node| issue_for_node(issues, node) }.uniq
+      end
+
+      def issues_for_nodes(nodes)
+        @issues_for_nodes ||= grouped_objects_for_nodes(
+          nodes,
+          Issue.all.includes(:author, :assignee, :project),
+          self.class.data_attribute
+        )
+      end
+
+      private
+
+      def issue_for_node(issues, node)
+        issues[node.attr(self.class.data_attribute).to_i]
+      end
+    end
+  end
+end

lib/banzai/reference_parser/label_parser.rb

+module Banzai
+  module ReferenceParser
+    class LabelParser < BaseParser
+      self.reference_type = :label
+
+      def references_relation
+        Label
+      end
+    end
+  end
+end

lib/banzai/reference_parser/merge_request_parser.rb

+module Banzai
+  module ReferenceParser
+    class MergeRequestParser < BaseParser
+      self.reference_type = :merge_request
+
+      def references_relation
+        MergeRequest.includes(:author, :assignee, :target_project)
+      end
+    end
+  end
+end

lib/banzai/reference_parser/milestone_parser.rb

+module Banzai
+  module ReferenceParser
+    class MilestoneParser < BaseParser
+      self.reference_type = :milestone
+
+      def references_relation
+        Milestone
+      end
+    end
+  end
+end

lib/banzai/reference_parser/snippet_parser.rb

+module Banzai
+  module ReferenceParser
+    class SnippetParser < BaseParser
+      self.reference_type = :snippet
+
+      def references_relation
+        Snippet
+      end
+    end
+  end
+end

lib/banzai/reference_parser/user_parser.rb

+module Banzai
+  module ReferenceParser
+    class UserParser < BaseParser
+      self.reference_type = :user
+
+      def referenced_by(nodes)
+        group_ids = []
+        user_ids = []
+        project_ids = []
+
+        nodes.each do |node|
+          if node.has_attribute?('data-group')
+            group_ids << node.attr('data-group').to_i
+          elsif node.has_attribute?(self.class.data_attribute)
+            user_ids << node.attr(self.class.data_attribute).to_i
+          elsif node.has_attribute?('data-project')
+            project_ids << node.attr('data-project').to_i
+          end
+        end
+
+        find_users_for_groups(group_ids) | find_users(user_ids) |
+          find_users_for_projects(project_ids)
+      end
+
+      def nodes_visible_to_user(user, nodes)
+        group_attr = 'data-group'
+        groups = lazy { grouped_objects_for_nodes(nodes, Group, group_attr) }
+        visible = []
+        remaining = []
+
+        nodes.each do |node|
+          if node.has_attribute?(group_attr)
+            node_group = groups[node.attr(group_attr).to_i]
+
+            if node_group &&
+              can?(user, :read_group, node_group)
+              visible << node
+            end
+          # Remaining nodes will be processed by the parent class'
+          # implementation of this method.
+          else
+            remaining << node
+          end
+        end
+
+        visible + super(current_user, remaining)
+      end
+
+      def nodes_user_can_reference(current_user, nodes)
+        project_attr = 'data-project'
+        author_attr = 'data-author'
+
+        projects = lazy { projects_for_nodes(nodes) }
+        users = lazy { grouped_objects_for_nodes(nodes, User, author_attr) }
+
+        nodes.select do |node|
+          project_id = node.attr(project_attr)
+          user_id = node.attr(author_attr)
+
+          if project && project_id && project.id == project_id.to_i
+            true
+          elsif project_id && user_id
+            project = projects[project_id.to_i]
+            user = users[user_id.to_i]
+
+            project && user ? project.team.member?(user) : false
+          else
+            true
+          end
+        end
+      end
+
+      def find_users(ids)
+        return [] if ids.empty?
+
+        User.where(id: ids).to_a
+      end
+
+      def find_users_for_groups(ids)
+        return [] if ids.empty?
+
+        User.joins(:group_members).where(members: { source_id: ids }).to_a
+      end
+
+      def find_users_for_projects(ids)
+        return [] if ids.empty?
+
+        Project.where(id: ids).flat_map { |p| p.team.members.to_a }
+      end
+    end
+  end
+end

lib/gitlab/reference_extractor.rb

@@ -4,10 +4,9 @@ module Gitlab
     REFERABLES = %i(user issue label milestone merge_request snippet commit commit_range)
     attr_accessor :project, :current_user, :author
 
-    def initialize(project, current_user = nil, author = nil)
+    def initialize(project, current_user = nil)
       @project = project
       @current_user = current_user
-      @author = author
 
       @references = {}
 
@@ -18,17 +17,21 @@ module Gitlab
       super(text, context.merge(project: project))
     end
 
+    def references(type)
+      super(type, project, current_user)
+    end
+
     REFERABLES.each do |type|
       define_method("#{type}s") do
-        @references[type] ||= references(type, reference_context)
+        @references[type] ||= references(type)
       end
     end
 
     def issues
       if project && project.jira_tracker?
-        @references[:external_issue] ||= references(:external_issue, reference_context)
+        @references[:external_issue] ||= references(:external_issue)
       else
-        @references[:issue] ||= references(:issue, reference_context)
+        @references[:issue] ||= references(:issue)
       end
     end
 
@@ -46,11 +49,5 @@ module Gitlab
 
       @pattern = Regexp.union(patterns.compact)
     end
-
-    private
-
-    def reference_context
-      { project: project, current_user: current_user, author: author }
-    end
   end
 end

spec/lib/banzai/filter/commit_range_reference_filter_spec.rb

@@ -98,11 +98,6 @@ describe Banzai::Filter::CommitRangeReferenceFilter, lib: true do
       expect(link).not_to match %r(https?://)
       expect(link).to eq urls.namespace_project_compare_url(project.namespace, project, from: commit1.id, to: commit2.id, only_path: true)
     end
-
-    it 'adds to the results hash' do
-      result = reference_pipeline_result("See #{reference}")
-      expect(result[:references][:commit_range]).not_to be_empty
-    end
   end
 
   context 'cross-project reference' do
@@ -135,11 +130,6 @@ describe Banzai::Filter::CommitRangeReferenceFilter, lib: true do
       exp = act = "Fixed #{project2.to_reference}@#{commit1.id}...#{commit2.id.reverse}"
       expect(reference_filter(act).to_html).to eq exp
     end
-
-    it 'adds to the results hash' do
-      result = reference_pipeline_result("See #{reference}")
-      expect(result[:references][:commit_range]).not_to be_empty
-    end
   end
 
   context 'cross-project URL reference' do
@@ -173,10 +163,5 @@ describe Banzai::Filter::CommitRangeReferenceFilter, lib: true do
       exp = act = "Fixed #{project2.to_reference}@#{commit1.id}...#{commit2.id.reverse}"
       expect(reference_filter(act).to_html).to eq exp
     end
-
-    it 'adds to the results hash' do
-      result = reference_pipeline_result("See #{reference}")
-      expect(result[:references][:commit_range]).not_to be_empty
-    end
   end
 end

spec/lib/banzai/filter/commit_reference_filter_spec.rb

@@ -93,11 +93,6 @@ describe Banzai::Filter::CommitReferenceFilter, lib: true do
       expect(link).not_to match %r(https?://)
       expect(link).to eq urls.namespace_project_commit_url(project.namespace, project, reference, only_path: true)
     end
-
-    it 'adds to the results hash' do
-      result = reference_pipeline_result("See #{reference}")
-      expect(result[:references][:commit]).not_to be_empty
-    end
   end
 
   context 'cross-project reference' do
@@ -124,11 +119,6 @@ describe Banzai::Filter::CommitReferenceFilter, lib: true do
       exp = act = "Committed #{invalidate_reference(reference)}"
       expect(reference_filter(act).to_html).to eq exp
     end
-
-    it 'adds to the results hash' do
-      result = reference_pipeline_result("See #{reference}")
-      expect(result[:references][:commit]).not_to be_empty
-    end
   end
 
   context 'cross-project URL reference' do
@@ -154,10 +144,5 @@ describe Banzai::Filter::CommitReferenceFilter, lib: true do
       act = "Committed #{invalidate_reference(reference)}"
       expect(reference_filter(act).to_html).to match(/<a.+>#{Regexp.escape(invalidate_reference(reference))}<\/a>/)
     end
-
-    it 'adds to the results hash' do
-      result = reference_pipeline_result("See #{reference}")
-      expect(result[:references][:commit]).not_to be_empty
-    end
   end
 end

spec/lib/banzai/filter/issue_reference_filter_spec.rb

@@ -91,11 +91,6 @@ describe Banzai::Filter::IssueReferenceFilter, lib: true do
       expect(link).to eq helper.url_for_issue(issue.iid, project, only_path: true)
     end
 
-    it 'adds to the results hash' do
-      result = reference_pipeline_result("Fixed #{reference}")
-      expect(result[:references][:issue]).to eq [issue]
-    end
-
     it 'does not process links containing issue numbers followed by text' do
       href = "#{reference}st"
       doc = reference_filter("<a href='#{href}'></a>")
@@ -136,11 +131,6 @@ describe Banzai::Filter::IssueReferenceFilter, lib: true do
 
       expect(reference_filter(act).to_html).to eq exp
     end
-
-    it 'adds to the results hash' do
-      result = reference_pipeline_result("Fixed #{reference}")
-      expect(result[:references][:issue]).to eq [issue]
-    end
   end
 
   context 'cross-project URL reference' do
@@ -160,11 +150,6 @@ describe Banzai::Filter::IssueReferenceFilter, lib: true do
       doc = reference_filter("Fixed (#{reference}.)")
       expect(doc.to_html).to match(/\(<a.+>#{Regexp.escape(issue.to_reference(project))} \(comment 123\)<\/a>\.\)/)
     end
-
-    it 'adds to the results hash' do
-      result = reference_pipeline_result("Fixed #{reference}")
-      expect(result[:references][:issue]).to eq [issue]
-    end
   end
 
   context 'cross-project reference in link href' do
@@ -184,11 +169,6 @@ describe Banzai::Filter::IssueReferenceFilter, lib: true do
       doc = reference_filter("Fixed (#{reference}.)")
       expect(doc.to_html).to match(/\(<a.+>Reference<\/a>\.\)/)
     end
-
-    it 'adds to the results hash' do
-      result = reference_pipeline_result("Fixed #{reference}")
-      expect(result[:references][:issue]).to eq [issue]
-    end
   end
 
   context 'cross-project URL in link href' do
@@ -208,10 +188,5 @@ describe Banzai::Filter::IssueReferenceFilter, lib: true do
       doc = reference_filter("Fixed (#{reference}.)")
       expect(doc.to_html).to match(/\(<a.+>Reference<\/a>\.\)/)
     end
-
-    it 'adds to the results hash' do
-      result = reference_pipeline_result("Fixed #{reference}")
-      expect(result[:references][:issue]).to eq [issue]
-    end
   end
 end

spec/lib/banzai/filter/label_reference_filter_spec.rb

@@ -48,11 +48,6 @@ describe Banzai::Filter::LabelReferenceFilter, lib: true do
     expect(link).to eq urls.namespace_project_issues_path(project.namespace, project, label_name: label.name)
   end
 
-  it 'adds to the results hash' do
-    result = reference_pipeline_result("Label #{reference}")
-    expect(result[:references][:label]).to eq [label]
-  end
-
   describe 'label span element' do
     it 'includes default classes' do
       doc = reference_filter("Label #{reference}")
@@ -170,11 +165,6 @@ describe Banzai::Filter::LabelReferenceFilter, lib: true do
       expect(link).to have_attribute('data-label')
       expect(link.attr('data-label')).to eq label.id.to_s
     end
-
-    it 'adds to the results hash' do
-      result = reference_pipeline_result("Label #{reference}")
-      expect(result[:references][:label]).to eq [label]
-    end
   end
 
   describe 'cross project label references' do

spec/lib/banzai/filter/merge_request_reference_filter_spec.rb

@@ -78,11 +78,6 @@ describe Banzai::Filter::MergeRequestReferenceFilter, lib: true do
       expect(link).not_to match %r(https?://)
       expect(link).to eq urls.namespace_project_merge_request_url(project.namespace, project, merge, only_path: true)
     end
-
-    it 'adds to the results hash' do
-      result = reference_pipeline_result("Merge #{reference}")
-      expect(result[:references][:merge_request]).to eq [merge]
-    end
   end
 
   context 'cross-project reference' do
@@ -109,11 +104,6 @@ describe Banzai::Filter::MergeRequestReferenceFilter, lib: true do
 
       expect(reference_filter(act).to_html).to eq exp
     end
-
-    it 'adds to the results hash' do
-      result = reference_pipeline_result("Merge #{reference}")
-      expect(result[:references][:merge_request]).to eq [merge]
-    end
   end
 
   context 'cross-project URL reference' do
@@ -133,10 +123,5 @@ describe Banzai::Filter::MergeRequestReferenceFilter, lib: true do
       doc = reference_filter("Merge (#{reference}.)")
       expect(doc.to_html).to match(/\(<a.+>#{Regexp.escape(merge.to_reference(project))} \(diffs, comment 123\)<\/a>\.\)/)
     end
-
-    it 'adds to the results hash' do
-      result = reference_pipeline_result("Merge #{reference}")
-      expect(result[:references][:merge_request]).to eq [merge]
-    end
   end
 end

spec/lib/banzai/filter/milestone_reference_filter_spec.rb

@@ -48,11 +48,6 @@ describe Banzai::Filter::MilestoneReferenceFilter, lib: true do
       namespace_project_milestone_path(project.namespace, project, milestone)
   end
 
-  it 'adds to the results hash' do
-    result = reference_pipeline_result("Milestone #{reference}")
-    expect(result[:references][:milestone]).to eq [milestone]
-  end
-
   context 'Integer-based references' do
     it 'links to a valid reference' do
       doc = reference_filter("See #{reference}")
@@ -151,11 +146,6 @@ describe Banzai::Filter::MilestoneReferenceFilter, lib: true do
       expect(link).to have_attribute('data-milestone')
       expect(link.attr('data-milestone')).to eq milestone.id.to_s
     end
-
-    it 'adds to the results hash' do
-      result = reference_pipeline_result("Milestone #{reference}")
-      expect(result[:references][:milestone]).to eq [milestone]
-    end
   end
 
   describe 'cross project milestone references' do

spec/lib/banzai/filter/redactor_filter_spec.rb

@@ -16,11 +16,23 @@ describe Banzai::Filter::RedactorFilter, lib: true do
   end
 
   context 'with data-project' do
+    let(:parser_class) do
+      Class.new(Banzai::ReferenceParser::BaseParser) do
+        self.reference_type = :test
+      end
+    end
+
+    before do
+      allow(Banzai::ReferenceParser).to receive(:[]).
+        with('test').
+        and_return(parser_class)
+    end
+
     it 'removes unpermitted Project references' do
       user = create(:user)
       project = create(:empty_project)
 
-      link = reference_link(project: project.id, reference_filter: 'ReferenceFilter')
+      link = reference_link(project: project.id, reference_type: 'test')
       doc = filter(link, current_user: user)
 
       expect(doc.css('a').length).to eq 0
@@ -31,14 +43,14 @@ describe Banzai::Filter::RedactorFilter, lib: true do
       project = create(:empty_project)
       project.team << [user, :master]
 
-      link = reference_link(project: project.id, reference_filter: 'ReferenceFilter')
+      link = reference_link(project: project.id, reference_type: 'test')
       doc = filter(link, current_user: user)
 
       expect(doc.css('a').length).to eq 1
     end
 
     it 'handles invalid Project references' do
-      link = reference_link(project: 12345, reference_filter: 'ReferenceFilter')
+      link = reference_link(project: 12345, reference_type: 'test')
 
       expect { filter(link) }.not_to raise_error
     end
@@ -51,7 +63,7 @@ describe Banzai::Filter::RedactorFilter, lib: true do
         project = create(:empty_project, :public)
         issue = create(:issue, :confidential, project: project)
 
-        link = reference_link(project: project.id, issue: issue.id, reference_filter: 'IssueReferenceFilter')
+        link = reference_link(project: project.id, issue: issue.id, reference_type: 'issue')
         doc = filter(link, current_user: non_member)
 
         expect(doc.css('a').length).to eq 0
@@ -62,7 +74,7 @@ describe Banzai::Filter::RedactorFilter, lib: true do
         project = create(:empty_project, :public)
         issue = create(:issue, :confidential, project: project, author: author)
 
-        link = reference_link(project: project.id, issue: issue.id, reference_filter: 'IssueReferenceFilter')
+        link = reference_link(project: project.id, issue: issue.id, reference_type: 'issue')
         doc = filter(link, current_user: author)
 
         expect(doc.css('a').length).to eq 1
@@ -73,7 +85,7 @@ describe Banzai::Filter::RedactorFilter, lib: true do
         project = create(:empty_project, :public)
         issue = create(:issue, :confidential, project: project, assignee: assignee)
 
-        link = reference_link(project: project.id, issue: issue.id, reference_filter: 'IssueReferenceFilter')
+        link = reference_link(project: project.id, issue: issue.id, reference_type: 'issue')
         doc = filter(link, current_user: assignee)
 
         expect(doc.css('a').length).to eq 1
@@ -85,7 +97,7 @@ describe Banzai::Filter::RedactorFilter, lib: true do
         project.team << [member, :developer]
         issue = create(:issue, :confidential, project: project)
 
-        link = reference_link(project: project.id, issue: issue.id, reference_filter: 'IssueReferenceFilter')
+        link = reference_link(project: project.id, issue: issue.id, reference_type: 'issue')
         doc = filter(link, current_user: member)
 
         expect(doc.css('a').length).to eq 1
@@ -96,7 +108,7 @@ describe Banzai::Filter::RedactorFilter, lib: true do
         project = create(:empty_project, :public)
         issue = create(:issue, :confidential, project: project)
 
-        link = reference_link(project: project.id, issue: issue.id, reference_filter: 'IssueReferenceFilter')
+        link = reference_link(project: project.id, issue: issue.id, reference_type: 'issue')
         doc = filter(link, current_user: admin)
 
         expect(doc.css('a').length).to eq 1
@@ -108,7 +120,7 @@ describe Banzai::Filter::RedactorFilter, lib: true do
       project = create(:empty_project, :public)
       issue = create(:issue, project: project)
 
-      link = reference_link(project: project.id, issue: issue.id, reference_filter: 'IssueReferenceFilter')
+      link = reference_link(project: project.id, issue: issue.id, reference_type: 'issue')
       doc = filter(link, current_user: user)
 
       expect(doc.css('a').length).to eq 1
@@ -121,7 +133,7 @@ describe Banzai::Filter::RedactorFilter, lib: true do
         user = create(:user)
         group = create(:group, :private)
 
-        link = reference_link(group: group.id, reference_filter: 'UserReferenceFilter')
+        link = reference_link(group: group.id, reference_type: 'user')
         doc = filter(link, current_user: user)
 
         expect(doc.css('a').length).to eq 0
@@ -132,14 +144,14 @@ describe Banzai::Filter::RedactorFilter, lib: true do
         group = create(:group, :private)
         group.add_developer(user)
 
-        link = reference_link(group: group.id, reference_filter: 'UserReferenceFilter')
+        link = reference_link(group: group.id, reference_type: 'user')
         doc = filter(link, current_user: user)
 
         expect(doc.css('a').length).to eq 1
       end
 
       it 'handles invalid Group references' do
-        link = reference_link(group: 12345, reference_filter: 'UserReferenceFilter')
+        link = reference_link(group: 12345, reference_type: 'user')
 
         expect { filter(link) }.not_to raise_error
       end
@@ -149,7 +161,7 @@ describe Banzai::Filter::RedactorFilter, lib: true do
       it 'allows any User reference' do
         user = create(:user)
 
-        link = reference_link(user: user.id, reference_filter: 'UserReferenceFilter')
+        link = reference_link(user: user.id, reference_type: 'user')
         doc = filter(link)
 
         expect(doc.css('a').length).to eq 1

spec/lib/banzai/filter/reference_gatherer_filter_spec.rb

-require 'spec_helper'
-
-describe Banzai::Filter::ReferenceGathererFilter, lib: true do
-  include ActionView::Helpers::UrlHelper
-  include FilterSpecHelper
-
-  def reference_link(data)
-    link_to('text', '', class: 'gfm', data: data)
-  end
-
-  context "for issue references" do
-
-    context 'with data-project' do
-      it 'removes unpermitted Project references' do
-        user = create(:user)
-        project = create(:empty_project)
-        issue = create(:issue, project: project)
-
-        link = reference_link(project: project.id, issue: issue.id, reference_filter: 'IssueReferenceFilter')
-        result = pipeline_result(link, current_user: user)
-
-        expect(result[:references][:issue]).to be_empty
-      end
-
-      it 'allows permitted Project references' do
-        user = create(:user)
-        project = create(:empty_project)
-        issue = create(:issue, project: project)
-        project.team << [user, :master]
-
-        link = reference_link(project: project.id, issue: issue.id, reference_filter: 'IssueReferenceFilter')
-        result = pipeline_result(link, current_user: user)
-
-        expect(result[:references][:issue]).to eq([issue])
-      end
-
-      it 'handles invalid Project references' do
-        link = reference_link(project: 12345, issue: 12345, reference_filter: 'IssueReferenceFilter')
-
-        expect { pipeline_result(link) }.not_to raise_error
-      end
-    end
-  end
-
-  context "for user references" do
-
-    context 'with data-group' do
-      it 'removes unpermitted Group references' do
-        user = create(:user)
-        group = create(:group)
-
-        link = reference_link(group: group.id, reference_filter: 'UserReferenceFilter')
-        result = pipeline_result(link, current_user: user)
-
-        expect(result[:references][:user]).to be_empty
-      end
-
-      it 'allows permitted Group references' do
-        user = create(:user)
-        group = create(:group)
-        group.add_developer(user)
-
-        link = reference_link(group: group.id, reference_filter: 'UserReferenceFilter')
-        result = pipeline_result(link, current_user: user)
-
-        expect(result[:references][:user]).to eq([user])
-      end
-
-      it 'handles invalid Group references' do
-        link = reference_link(group: 12345, reference_filter: 'UserReferenceFilter')
-
-        expect { pipeline_result(link) }.not_to raise_error
-      end
-    end
-
-    context 'with data-user' do
-      it 'allows any User reference' do
-        user = create(:user)
-
-        link = reference_link(user: user.id, reference_filter: 'UserReferenceFilter')
-        result = pipeline_result(link)
-
-        expect(result[:references][:user]).to eq([user])
-      end
-    end
-  end
-end

spec/lib/banzai/filter/snippet_reference_filter_spec.rb

@@ -77,11 +77,6 @@ describe Banzai::Filter::SnippetReferenceFilter, lib: true do
       expect(link).not_to match %r(https?://)
       expect(link).to eq urls.namespace_project_snippet_url(project.namespace, project, snippet, only_path: true)
     end
-
-    it 'adds to the results hash' do
-      result = reference_pipeline_result("Snippet #{reference}")
-      expect(result[:references][:snippet]).to eq [snippet]
-    end
   end
 
   context 'cross-project reference' do
@@ -107,11 +102,6 @@ describe Banzai::Filter::SnippetReferenceFilter, lib: true do
 
       expect(reference_filter(act).to_html).to eq exp
     end
-
-    it 'adds to the results hash' do
-      result = reference_pipeline_result("Snippet #{reference}")
-      expect(result[:references][:snippet]).to eq [snippet]
-    end
   end
 
   context 'cross-project URL reference' do
@@ -137,10 +127,5 @@ describe Banzai::Filter::SnippetReferenceFilter, lib: true do
 
       expect(reference_filter(act).to_html).to match(/<a.+>#{Regexp.escape(invalidate_reference(reference))}<\/a>/)
     end
-
-    it 'adds to the results hash' do
-      result = reference_pipeline_result("Snippet #{reference}")
-      expect(result[:references][:snippet]).to eq [snippet]
-    end
   end
 end

spec/lib/banzai/filter/user_reference_filter_spec.rb

@@ -31,28 +31,22 @@ describe Banzai::Filter::UserReferenceFilter, lib: true do
     end
 
     it 'supports a special @all mention' do
-      doc = reference_filter("Hey #{reference}")
+      doc = reference_filter("Hey #{reference}", author: user)
       expect(doc.css('a').length).to eq 1
       expect(doc.css('a').first.attr('href'))
         .to eq urls.namespace_project_url(project.namespace, project)
     end
 
-    context "when the author is a member of the project" do
+    it 'includes a data-author attribute when there is an author' do
+      doc = reference_filter(reference, author: user)
 
-      it 'adds to the results hash' do
-        result = reference_pipeline_result("Hey #{reference}", author: project.creator)
-        expect(result[:references][:user]).to eq [project.creator]
-      end
+      expect(doc.css('a').first.attr('data-author')).to eq(user.id.to_s)
     end
 
-    context "when the author is not a member of the project" do
-
-      let(:other_user) { create(:user) }
+    it 'does not include a data-author attribute when there is no author' do
+      doc = reference_filter(reference)
 
-      it "doesn't add to the results hash" do
-        result = reference_pipeline_result("Hey #{reference}", author: other_user)
-        expect(result[:references][:user]).to eq []
-      end
+      expect(doc.css('a').first.has_attribute?('data-author')).to eq(false)
     end
   end
 
@@ -83,11 +77,6 @@ describe Banzai::Filter::UserReferenceFilter, lib: true do
       expect(link).to have_attribute('data-user')
       expect(link.attr('data-user')).to eq user.namespace.owner_id.to_s
     end
-
-    it 'adds to the results hash' do
-      result = reference_pipeline_result("Hey #{reference}")
-      expect(result[:references][:user]).to eq [user]
-    end
   end
 
   context 'mentioning a group' do
@@ -106,11 +95,6 @@ describe Banzai::Filter::UserReferenceFilter, lib: true do
       expect(link).to have_attribute('data-group')
       expect(link.attr('data-group')).to eq group.id.to_s
     end
-
-    it 'adds to the results hash' do
-      result = reference_pipeline_result("Hey #{reference}")
-      expect(result[:references][:user]).to eq group.users
-    end
   end
 
   it 'links with adjacent text' do
@@ -151,10 +135,5 @@ describe Banzai::Filter::UserReferenceFilter, lib: true do
       expect(link).to have_attribute('data-user')
       expect(link.attr('data-user')).to eq user.namespace.owner_id.to_s
     end
-
-    it 'adds to the results hash' do
-      result = reference_pipeline_result("Hey #{reference}")
-      expect(result[:references][:user]).to eq [user]
-    end
   end
 end

spec/lib/banzai/reference_parser/base_parser_spec.rb

+require 'spec_helper'
+
+describe Banzai::ReferenceParser::BaseParser, lib: true do
+  include ReferenceParserHelpers
+
+  let(:user) { create(:user) }
+  let(:project) { create(:empty_project, :public) }
+
+  subject do
+    klass = Class.new(described_class) do
+      self.reference_type = :foo
+    end
+
+    klass.new(project, user)
+  end
+
+  describe '.reference_type=' do
+    it 'sets the reference type' do
+      dummy = Class.new(described_class)
+      dummy.reference_type = :foo
+
+      expect(dummy.reference_type).to eq(:foo)
+    end
+  end
+
+  describe '#nodes_visible_to_user' do
+    let(:link) { empty_html_link }
+
+    context 'when the link has a data-project attribute' do
+      it 'returns the nodes if the attribute value equals the current project ID' do
+        link['data-project'] = project.id.to_s
+
+        expect(Ability.abilities).not_to receive(:allowed?)
+        expect(subject.nodes_visible_to_user(user, [link])).to eq([link])
+      end
+
+      it 'returns the nodes if the user can read the project' do
+        other_project = create(:empty_project, :public)
+
+        link['data-project'] = other_project.id.to_s
+
+        expect(Ability.abilities).to receive(:allowed?).
+          with(user, :read_project, other_project).
+          and_return(true)
+
+        expect(subject.nodes_visible_to_user(user, [link])).to eq([link])
+      end
+
+      it 'returns an empty Array when the attribute value is empty' do
+        link['data-project'] = ''
+
+        expect(subject.nodes_visible_to_user(user, [link])).to eq([])
+      end
+
+      it 'returns an empty Array when the user can not read the project' do
+        other_project = create(:empty_project, :public)
+
+        link['data-project'] = other_project.id.to_s
+
+        expect(Ability.abilities).to receive(:allowed?).
+          with(user, :read_project, other_project).
+          and_return(false)
+
+        expect(subject.nodes_visible_to_user(user, [link])).to eq([])
+      end
+    end
+
+    context 'when the link does not have a data-project attribute' do
+      it 'returns the nodes' do
+        expect(subject.nodes_visible_to_user(user, [link])).to eq([link])
+      end
+    end
+  end
+
+  describe '#nodes_user_can_reference' do
+    it 'returns the nodes' do
+      link = double(:link)
+
+      expect(subject.nodes_user_can_reference(user, [link])).to eq([link])
+    end
+  end
+
+  describe '#referenced_by' do
+    context 'when references_relation is implemented' do
+      it 'returns a collection of objects' do
+        links = Nokogiri::HTML.fragment("<a data-foo='#{user.id}'></a>").
+          children
+
+        expect(subject).to receive(:references_relation).and_return(User)
+        expect(subject.referenced_by(links)).to eq([user])
+      end
+    end
+
+    context 'when references_relation is not implemented' do
+      it 'raises NotImplementedError' do
+        links = Nokogiri::HTML.fragment('<a data-foo="1"></a>').children
+
+        expect { subject.referenced_by(links) }.
+          to raise_error(NotImplementedError)
+      end
+    end
+  end
+
+  describe '#references_relation' do
+    it 'raises NotImplementedError' do
+      expect { subject.references_relation }.to raise_error(NotImplementedError)
+    end
+  end
+
+  describe '#gather_attributes_per_project' do
+    it 'returns a Hash containing attribute values per project' do
+      link = Nokogiri::HTML.fragment('<a data-project="1" data-foo="2"></a>').
+        children[0]
+
+      hash = subject.gather_attributes_per_project([link], 'data-foo')
+
+      expect(hash).to be_an_instance_of(Hash)
+
+      expect(hash[1].to_a).to eq(['2'])
+    end
+  end
+
+  describe '#grouped_objects_for_nodes' do
+    it 'returns a Hash grouping objects per ID' do
+      nodes = [double(:node)]
+
+      expect(subject).to receive(:unique_attribute_values).
+        with(nodes, 'data-user').
+        and_return([user.id])
+
+      hash = subject.grouped_objects_for_nodes(nodes, User, 'data-user')
+
+      expect(hash).to eq({ user.id => user })
+    end
+
+    it 'returns an empty Hash when the list of nodes is empty' do
+      expect(subject.grouped_objects_for_nodes([], User, 'data-user')).to eq({})
+    end
+  end
+
+  describe '#unique_attribute_values' do
+    it 'returns an Array of unique values' do
+      link = double(:link)
+
+      expect(link).to receive(:has_attribute?).
+        with('data-foo').
+        twice.
+        and_return(true)
+
+      expect(link).to receive(:attr).
+        with('data-foo').
+        twice.
+        and_return('1')
+
+      nodes = [link, link]
+
+      expect(subject.unique_attribute_values(nodes, 'data-foo')).to eq(['1'])
+    end
+  end
+
+  describe '#process' do
+    it 'gathers the references for every node matching the reference type' do
+      dummy = Class.new(described_class) do
+        self.reference_type = :test
+      end
+
+      instance = dummy.new(project, user)
+      document = Nokogiri::HTML.fragment('<a class="gfm"></a><a class="gfm" data-reference-type="test"></a>')
+
+      expect(instance).to receive(:gather_references).
+        with([document.children[1]]).
+        and_return([user])
+
+      expect(instance.process([document])).to eq([user])
+    end
+  end
+
+  describe '#gather_references' do
+    let(:link) { double(:link) }
+
+    it 'does not process links a user can not reference' do
+      expect(subject).to receive(:nodes_user_can_reference).
+        with(user, [link]).
+        and_return([])
+
+      expect(subject).to receive(:referenced_by).with([])
+
+      subject.gather_references([link])
+    end
+
+    it 'does not process links a user can not see' do
+      expect(subject).to receive(:nodes_user_can_reference).
+        with(user, [link]).
+        and_return([link])
+
+      expect(subject).to receive(:nodes_visible_to_user).
+        with(user, [link]).
+        and_return([])
+
+      expect(subject).to receive(:referenced_by).with([])
+
+      subject.gather_references([link])
+    end
+
+    it 'returns the references if a user can reference and see a link' do
+      expect(subject).to receive(:nodes_user_can_reference).
+        with(user, [link]).
+        and_return([link])
+
+      expect(subject).to receive(:nodes_visible_to_user).
+        with(user, [link]).
+        and_return([link])
+
+      expect(subject).to receive(:referenced_by).with([link])
+
+      subject.gather_references([link])
+    end
+  end
+
+  describe '#can?' do
+    it 'delegates the permissions check to the Ability class' do
+      user = double(:user)
+
+      expect(Ability.abilities).to receive(:allowed?).
+        with(user, :read_project, project)
+
+      subject.can?(user, :read_project, project)
+    end
+  end
+
+  describe '#find_projects_for_hash_keys' do
+    it 'returns a list of Projects' do
+      expect(subject.find_projects_for_hash_keys(project.id => project)).
+        to eq([project])
+    end
+  end
+end

spec/lib/banzai/reference_parser/commit_parser_spec.rb

+require 'spec_helper'
+
+describe Banzai::ReferenceParser::CommitParser, lib: true do
+  include ReferenceParserHelpers
+
+  let(:project) { create(:empty_project, :public) }
+  let(:user) { create(:user) }
+  subject { described_class.new(project, user) }
+  let(:link) { empty_html_link }
+
+  describe '#referenced_by' do
+    context 'when the link has a data-project attribute' do
+      before do
+        link['data-project'] = project.id.to_s
+      end
+
+      context 'when the link has a data-commit attribute' do
+        before do
+          link['data-commit'] = '123'
+        end
+
+        it 'returns an Array of commits' do
+          commit = double(:commit)
+
+          allow_any_instance_of(Project).to receive(:valid_repo?).
+            and_return(true)
+
+          expect(subject).to receive(:find_commits).
+            with(project, ['123']).
+            and_return([commit])
+
+          expect(subject.referenced_by([link])).to eq([commit])
+        end
+
+        it 'returns an empty Array when the commit could not be found' do
+          allow_any_instance_of(Project).to receive(:valid_repo?).
+            and_return(true)
+
+          expect(subject).to receive(:find_commits).
+            with(project, ['123']).
+            and_return([])
+
+          expect(subject.referenced_by([link])).to eq([])
+        end
+
+        it 'skips projects without valid repositories' do
+          allow_any_instance_of(Project).to receive(:valid_repo?).
+            and_return(false)
+
+          expect(subject.referenced_by([link])).to eq([])
+        end
+      end
+
+      context 'when the link does not have a data-commit attribute' do
+        it 'returns an empty Array' do
+          allow_any_instance_of(Project).to receive(:valid_repo?).
+            and_return(true)
+
+          expect(subject.referenced_by([link])).to eq([])
+        end
+      end
+    end
+
+    context 'when the link does not have a data-project attribute' do
+      it 'returns an empty Array' do
+        allow_any_instance_of(Project).to receive(:valid_repo?).
+          and_return(true)
+
+        expect(subject.referenced_by([link])).to eq([])
+      end
+    end
+  end
+
+  describe '#commit_ids_per_project' do
+    before do
+      link['data-project'] = project.id.to_s
+    end
+
+    it 'returns a Hash containing commit IDs per project' do
+      link['data-commit'] = '123'
+
+      hash = subject.commit_ids_per_project([link])
+
+      expect(hash).to be_an_instance_of(Hash)
+
+      expect(hash[project.id].to_a).to eq(['123'])
+    end
+
+    it 'does not add a project when the data-commit attribute is empty' do
+      hash = subject.commit_ids_per_project([link])
+
+      expect(hash).to be_empty
+    end
+  end
+
+  describe '#find_commits' do
+    it 'returns an Array of commit objects' do
+      commit = double(:commit)
+
+      expect(project).to receive(:commit).with('123').and_return(commit)
+      expect(project).to receive(:valid_repo?).and_return(true)
+
+      expect(subject.find_commits(project, %w{123})).to eq([commit])
+    end
+
+    it 'skips commit IDs for which no commit could be found' do
+      expect(project).to receive(:commit).with('123').and_return(nil)
+      expect(project).to receive(:valid_repo?).and_return(true)
+
+      expect(subject.find_commits(project, %w{123})).to eq([])
+    end
+  end
+end

spec/lib/banzai/reference_parser/commit_range_parser_spec.rb

+require 'spec_helper'
+
+describe Banzai::ReferenceParser::CommitRangeParser, lib: true do
+  include ReferenceParserHelpers
+
+  let(:project) { create(:empty_project, :public) }
+  let(:user) { create(:user) }
+  subject { described_class.new(project, user) }
+  let(:link) { empty_html_link }
+
+  describe '#referenced_by' do
+    context 'when the link has a data-project attribute' do
+      before do
+        link['data-project'] = project.id.to_s
+      end
+
+      context 'when the link as a data-commit-range attribute' do
+        before do
+          link['data-commit-range'] = '123..456'
+        end
+
+        it 'returns an Array of commit ranges' do
+          range = double(:range)
+
+          expect(subject).to receive(:find_object).
+            with(project, '123..456').
+            and_return(range)
+
+          expect(subject.referenced_by([link])).to eq([range])
+        end
+
+        it 'returns an empty Array when the commit range could not be found' do
+          expect(subject).to receive(:find_object).
+            with(project, '123..456').
+            and_return(nil)
+
+          expect(subject.referenced_by([link])).to eq([])
+        end
+      end
+
+      context 'when the link does not have a data-commit-range attribute' do
+        it 'returns an empty Array' do
+          expect(subject.referenced_by([link])).to eq([])
+        end
+      end
+    end
+
+    context 'when the link does not have a data-project attribute' do
+      it 'returns an empty Array' do
+        expect(subject.referenced_by([link])).to eq([])
+      end
+    end
+  end
+
+  describe '#commit_range_ids_per_project' do
+    before do
+      link['data-project'] = project.id.to_s
+    end
+
+    it 'returns a Hash containing range IDs per project' do
+      link['data-commit-range'] = '123..456'
+
+      hash = subject.commit_range_ids_per_project([link])
+
+      expect(hash).to be_an_instance_of(Hash)
+
+      expect(hash[project.id].to_a).to eq(['123..456'])
+    end
+
+    it 'does not add a project when the data-commit-range attribute is empty' do
+      hash = subject.commit_range_ids_per_project([link])
+
+      expect(hash).to be_empty
+    end
+  end
+
+  describe '#find_ranges' do
+    it 'returns an Array of range objects' do
+      range = double(:commit)
+
+      expect(subject).to receive(:find_object).
+        with(project, '123..456').
+        and_return(range)
+
+      expect(subject.find_ranges(project, ['123..456'])).to eq([range])
+    end
+
+    it 'skips ranges that could not be found' do
+      expect(subject).to receive(:find_object).
+        with(project, '123..456').
+        and_return(nil)
+
+      expect(subject.find_ranges(project, ['123..456'])).to eq([])
+    end
+  end
+
+  describe '#find_object' do
+    let(:range) { double(:range) }
+
+    before do
+      expect(CommitRange).to receive(:new).and_return(range)
+    end
+
+    context 'when the range has valid commits' do
+      it 'returns the commit range' do
+        expect(range).to receive(:valid_commits?).and_return(true)
+
+        expect(subject.find_object(project, '123..456')).to eq(range)
+      end
+    end
+
+    context 'when the range does not have any valid commits' do
+      it 'returns nil' do
+        expect(range).to receive(:valid_commits?).and_return(false)
+
+        expect(subject.find_object(project, '123..456')).to be_nil
+      end
+    end
+  end
+end

spec/lib/banzai/reference_parser/external_issue_parser_spec.rb

+require 'spec_helper'
+
+describe Banzai::ReferenceParser::ExternalIssueParser, lib: true do
+  include ReferenceParserHelpers
+
+  let(:project) { create(:empty_project, :public) }
+  let(:user) { create(:user) }
+  subject { described_class.new(project, user) }
+  let(:link) { empty_html_link }
+
+  describe '#referenced_by' do
+    context 'when the link has a data-project attribute' do
+      before do
+        link['data-project'] = project.id.to_s
+      end
+
+      context 'when the link has a data-external-issue attribute' do
+        it 'returns an Array of ExternalIssue instances' do
+          link['data-external-issue'] = '123'
+
+          refs = subject.referenced_by([link])
+
+          expect(refs).to eq([ExternalIssue.new('123', project)])
+        end
+      end
+
+      context 'when the link does not have a data-external-issue attribute' do
+        it 'returns an empty Array' do
+          expect(subject.referenced_by([link])).to eq([])
+        end
+      end
+    end
+
+    context 'when the link does not have a data-project attribute' do
+      it 'returns an empty Array' do
+        expect(subject.referenced_by([link])).to eq([])
+      end
+    end
+  end
+
+  describe '#issue_ids_per_project' do
+    before do
+      link['data-project'] = project.id.to_s
+    end
+
+    it 'returns a Hash containing range IDs per project' do
+      link['data-external-issue'] = '123'
+
+      hash = subject.issue_ids_per_project([link])
+
+      expect(hash).to be_an_instance_of(Hash)
+
+      expect(hash[project.id].to_a).to eq(['123'])
+    end
+
+    it 'does not add a project when the data-external-issue attribute is empty' do
+      hash = subject.issue_ids_per_project([link])
+
+      expect(hash).to be_empty
+    end
+  end
+end

spec/lib/banzai/reference_parser/issue_parser_spec.rb

+require 'spec_helper'
+
+describe Banzai::ReferenceParser::IssueParser, lib: true do
+  include ReferenceParserHelpers
+
+  let(:project) { create(:empty_project, :public) }
+  let(:user) { create(:user) }
+  let(:issue) { create(:issue, project: project) }
+  subject { described_class.new(project, user) }
+  let(:link) { empty_html_link }
+
+  describe '#nodes_visible_to_user' do
+    context 'when the link has a data-issue attribute' do
+      before do
+        link['data-issue'] = issue.id.to_s
+      end
+
+      it 'returns the nodes when the user can read the issue' do
+        expect(Ability.abilities).to receive(:allowed?).
+          with(user, :read_issue, issue).
+          and_return(true)
+
+        expect(subject.nodes_visible_to_user(user, [link])).to eq([link])
+      end
+
+      it 'returns an empty Array when the user can not read the issue' do
+        expect(Ability.abilities).to receive(:allowed?).
+          with(user, :read_issue, issue).
+          and_return(false)
+
+        expect(subject.nodes_visible_to_user(user, [link])).to eq([])
+      end
+    end
+
+    context 'when the link does not have a data-issue attribute' do
+      it 'returns an empty Array' do
+        expect(subject.nodes_visible_to_user(user, [link])).to eq([])
+      end
+    end
+
+    context 'when the project uses an external issue tracker' do
+      it 'returns all nodes' do
+        link = double(:link)
+
+        expect(project).to receive(:external_issue_tracker).and_return(true)
+
+        expect(subject.nodes_visible_to_user(user, [link])).to eq([link])
+      end
+    end
+  end
+
+  describe '#referenced_by' do
+    context 'when the link has a data-issue attribute' do
+      context 'using an existing issue ID' do
+        before do
+          link['data-issue'] = issue.id.to_s
+        end
+
+        it 'returns an Array of issues' do
+          expect(subject.referenced_by([link])).to eq([issue])
+        end
+
+        it 'returns an empty Array when the list of nodes is empty' do
+          expect(subject.referenced_by([link])).to eq([issue])
+          expect(subject.referenced_by([])).to eq([])
+        end
+      end
+    end
+  end
+
+  describe '#issues_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({ issue.id => issue })
+    end
+  end
+end

spec/lib/banzai/reference_parser/label_parser_spec.rb

+require 'spec_helper'
+
+describe Banzai::ReferenceParser::LabelParser, lib: true do
+  include ReferenceParserHelpers
+
+  let(:project) { create(:empty_project, :public) }
+  let(:user) { create(:user) }
+  let(:label) { create(:label, project: project) }
+  subject { described_class.new(project, user) }
+  let(:link) { empty_html_link }
+
+  describe '#referenced_by' do
+    describe 'when the link has a data-label attribute' do
+      context 'using an existing label ID' do
+        it 'returns an Array of labels' do
+          link['data-label'] = label.id.to_s
+
+          expect(subject.referenced_by([link])).to eq([label])
+        end
+      end
+
+      context 'using a non-existing label ID' do
+        it 'returns an empty Array' do
+          link['data-label'] = ''
+
+          expect(subject.referenced_by([link])).to eq([])
+        end
+      end
+    end
+  end
+end

spec/lib/banzai/reference_parser/merge_request_parser_spec.rb

+require 'spec_helper'
+
+describe Banzai::ReferenceParser::MergeRequestParser, lib: true do
+  include ReferenceParserHelpers
+
+  let(:user) { create(:user) }
+  let(:merge_request) { create(:merge_request) }
+  subject { described_class.new(merge_request.target_project, user) }
+  let(:link) { empty_html_link }
+
+  describe '#referenced_by' do
+    describe 'when the link has a data-merge-request attribute' do
+      context 'using an existing merge request ID' do
+        it 'returns an Array of merge requests' do
+          link['data-merge-request'] = merge_request.id.to_s
+
+          expect(subject.referenced_by([link])).to eq([merge_request])
+        end
+      end
+
+      context 'using a non-existing merge request ID' do
+        it 'returns an empty Array' do
+          link['data-merge-request'] = ''
+
+          expect(subject.referenced_by([link])).to eq([])
+        end
+      end
+    end
+  end
+end

spec/lib/banzai/reference_parser/milestone_parser_spec.rb

+require 'spec_helper'
+
+describe Banzai::ReferenceParser::MilestoneParser, lib: true do
+  include ReferenceParserHelpers
+
+  let(:project) { create(:empty_project, :public) }
+  let(:user) { create(:user) }
+  let(:milestone) { create(:milestone, project: project) }
+  subject { described_class.new(project, user) }
+  let(:link) { empty_html_link }
+
+  describe '#referenced_by' do
+    describe 'when the link has a data-milestone attribute' do
+      context 'using an existing milestone ID' do
+        it 'returns an Array of milestones' do
+          link['data-milestone'] = milestone.id.to_s
+
+          expect(subject.referenced_by([link])).to eq([milestone])
+        end
+      end
+
+      context 'using a non-existing milestone ID' do
+        it 'returns an empty Array' do
+          link['data-milestone'] = ''
+
+          expect(subject.referenced_by([link])).to eq([])
+        end
+      end
+    end
+  end
+end

spec/lib/banzai/reference_parser/snippet_parser_spec.rb

+require 'spec_helper'
+
+describe Banzai::ReferenceParser::SnippetParser, lib: true do
+  include ReferenceParserHelpers
+
+  let(:project) { create(:empty_project, :public) }
+  let(:user) { create(:user) }
+  let(:snippet) { create(:snippet, project: project) }
+  subject { described_class.new(project, user) }
+  let(:link) { empty_html_link }
+
+  describe '#referenced_by' do
+    describe 'when the link has a data-snippet attribute' do
+      context 'using an existing snippet ID' do
+        it 'returns an Array of snippets' do
+          link['data-snippet'] = snippet.id.to_s
+
+          expect(subject.referenced_by([link])).to eq([snippet])
+        end
+      end
+
+      context 'using a non-existing snippet ID' do
+        it 'returns an empty Array' do
+          link['data-snippet'] = ''
+
+          expect(subject.referenced_by([link])).to eq([])
+        end
+      end
+    end
+  end
+end

spec/lib/banzai/reference_parser/user_parser_spec.rb

+require 'spec_helper'
+
+describe Banzai::ReferenceParser::UserParser, lib: true do
+  include ReferenceParserHelpers
+
+  let(:group) { create(:group) }
+  let(:user) { create(:user) }
+  let(:project) { create(:empty_project, :public, group: group, creator: user) }
+  subject { described_class.new(project, user) }
+  let(:link) { empty_html_link }
+
+  describe '#referenced_by' do
+    context 'when the link has a data-group attribute' do
+      context 'using an existing group ID' do
+        before do
+          link['data-group'] = project.group.id.to_s
+        end
+
+        it 'returns the users of the group' do
+          create(:group_member, group: group, user: user)
+
+          expect(subject.referenced_by([link])).to eq([user])
+        end
+
+        it 'returns an empty Array when the group has no users' do
+          expect(subject.referenced_by([link])).to eq([])
+        end
+      end
+
+      context 'using a non-existing group ID' do
+        it 'returns an empty Array' do
+          link['data-group'] = ''
+
+          expect(subject.referenced_by([link])).to eq([])
+        end
+      end
+    end
+
+    context 'when the link has a data-user attribute' do
+      it 'returns an Array of users' do
+        link['data-user'] = user.id.to_s
+
+        expect(subject.referenced_by([link])).to eq([user])
+      end
+    end
+
+    context 'when the link has a data-project attribute' do
+      context 'using an existing project ID' do
+        let(:contributor) { create(:user) }
+
+        before do
+          project.team << [user, :developer]
+          project.team << [contributor, :developer]
+        end
+
+        it 'returns the members of a project' do
+          link['data-project'] = project.id.to_s
+
+          # This uses an explicit sort to make sure this spec doesn't randomly
+          # fail when objects are returned in a different order.
+          refs = subject.referenced_by([link]).sort_by(&:id)
+
+          expect(refs).to eq([user, contributor])
+        end
+      end
+
+      context 'using a non-existing project ID' do
+        it 'returns an empty Array' do
+          link['data-project'] = ''
+
+          expect(subject.referenced_by([link])).to eq([])
+        end
+      end
+    end
+  end
+
+  describe '#nodes_visible_to_use?' do
+    context 'when the link has a data-group attribute' do
+      context 'using an existing group ID' do
+        before do
+          link['data-group'] = group.id.to_s
+        end
+
+        it 'returns the nodes if the user can read the group' do
+          expect(Ability.abilities).to receive(:allowed?).
+            with(user, :read_group, group).
+            and_return(true)
+
+          expect(subject.nodes_visible_to_user(user, [link])).to eq([link])
+        end
+
+        it 'returns an empty Array if the user can not read the group' do
+          expect(Ability.abilities).to receive(:allowed?).
+            with(user, :read_group, group).
+            and_return(false)
+
+          expect(subject.nodes_visible_to_user(user, [link])).to eq([])
+        end
+      end
+
+      context 'when the link does not have a data-group attribute' do
+        context 'with a data-project attribute' do
+          it 'returns the nodes if the attribute value equals the current project ID' do
+            link['data-project'] = project.id.to_s
+
+            expect(Ability.abilities).not_to receive(:allowed?)
+
+            expect(subject.nodes_visible_to_user(user, [link])).to eq([link])
+          end
+
+          it 'returns the nodes if the user can read the project' do
+            other_project = create(:empty_project, :public)
+
+            link['data-project'] = other_project.id.to_s
+
+            expect(Ability.abilities).to receive(:allowed?).
+              with(user, :read_project, other_project).
+              and_return(true)
+
+            expect(subject.nodes_visible_to_user(user, [link])).to eq([link])
+          end
+
+          it 'returns an empty Array if the user can not read the project' do
+            other_project = create(:empty_project, :public)
+
+            link['data-project'] = other_project.id.to_s
+
+            expect(Ability.abilities).to receive(:allowed?).
+              with(user, :read_project, other_project).
+              and_return(false)
+
+            expect(subject.nodes_visible_to_user(user, [link])).to eq([])
+          end
+        end
+
+        context 'without a data-project attribute' do
+          it 'returns the nodes' do
+            expect(subject.nodes_visible_to_user(user, [link])).to eq([link])
+          end
+        end
+      end
+    end
+  end
+
+  describe '#nodes_user_can_reference' do
+    context 'when the link has a data-author attribute' do
+      it 'returns the nodes when the user is a member of the project' do
+        other_project = create(:project)
+        other_project.team << [user, :developer]
+
+        link['data-project'] = other_project.id.to_s
+        link['data-author'] = user.id.to_s
+
+        expect(subject.nodes_user_can_reference(user, [link])).to eq([link])
+      end
+
+      it 'returns an empty Array when the project could not be found' do
+        link['data-project'] = ''
+        link['data-author'] = user.id.to_s
+
+        expect(subject.nodes_user_can_reference(user, [link])).to eq([])
+      end
+
+      it 'returns an empty Array when the user could not be found' do
+        other_project = create(:project)
+
+        link['data-project'] = other_project.id.to_s
+        link['data-author'] = ''
+
+        expect(subject.nodes_user_can_reference(user, [link])).to eq([])
+      end
+
+      it 'returns an empty Array when the user is not a team member' do
+        other_project = create(:project)
+
+        link['data-project'] = other_project.id.to_s
+        link['data-author'] = user.id.to_s
+
+        expect(subject.nodes_user_can_reference(user, [link])).to eq([])
+      end
+    end
+
+    context 'when the link does not have a data-author attribute' do
+      it 'returns the nodes' do
+        expect(subject.nodes_user_can_reference(user, [link])).to eq([link])
+      end
+    end
+  end
+end

spec/support/filter_spec_helper.rb

@@ -40,8 +40,7 @@ module FilterSpecHelper
 
     filters = [
       Banzai::Filter::AutolinkFilter,
-      described_class,
-      Banzai::Filter::ReferenceGathererFilter
+      described_class
     ]
 
     HTML::Pipeline.new(filters, context)

spec/support/reference_parser_helpers.rb

+module ReferenceParserHelpers
+  def empty_html_link
+    Nokogiri::HTML.fragment('<a></a>').children[0]
+  end
+end