Add support for cross project references for labels

app/models/label.rb

@@ -51,7 +51,8 @@ class Label < ActiveRecord::Base
   # Pattern used to extract label references from text
   def self.reference_pattern
     %r{
-      #{reference_prefix}
+      (#{Project.reference_pattern})?
+      #{Regexp.escape(reference_prefix)}
       (?:
         (?<label_id>\d+) | # Integer-based label ID, or
         (?<label_name>
@@ -62,6 +63,10 @@ class Label < ActiveRecord::Base
     }x
   end
 
+  def self.link_reference_pattern
+    nil
+  end
+
   # Returns the String necessary to reference this Label in Markdown
   #
   # format - Symbol format to use (default: :id, optional: :name)

lib/banzai/filter/label_reference_filter.rb

 module Banzai
   module Filter
     # HTML filter that replaces label references with links.
-    class LabelReferenceFilter < ReferenceFilter
-      # Public: Find label references in text
-      #
-      #   LabelReferenceFilter.references_in(text) do |match, id, name|
-      #     "<a href=...>#{Label.find(id)}</a>"
-      #   end
-      #
-      # text - String text to search.
-      #
-      # Yields the String match, an optional Integer label ID, and an optional
-      # String label name.
-      #
-      # Returns a String replaced with the return of the block.
-      def self.references_in(text)
-        text.gsub(Label.reference_pattern) do |match|
-          yield match, $~[:label_id].to_i, $~[:label_name]
-        end
-      end
-
-      def self.referenced_by(node)
-        { label: LazyReference.new(Label, node.attr("data-label")) }
+    class LabelReferenceFilter < AbstractReferenceFilter
+      def self.object_class
+        Label
       end
 
-      def call
-        replace_text_nodes_matching(Label.reference_pattern) do |content|
-          label_link_filter(content)
+      def find_object(project, id)
+        project.labels.find(id)
       end
 
-        replace_link_nodes_with_href(Label.reference_pattern) do |link, text|
-          label_link_filter(link, link_text: text)
+      def self.references_in(text, pattern = Label.reference_pattern)
+        text.gsub(pattern) do |match|
+          yield match, $~[:label_id].to_i, $~[:label_name], $~[:project], $~
         end
       end
 
-      # Replace label references in text with links to the label specified.
-      #
-      # text - String text to replace references in.
-      #
-      # Returns a String with label references replaced with links. All links
-      # have `gfm` and `gfm-label` class names attached for styling.
-      def label_link_filter(text, link_text: nil)
-        project = context[:project]
-
-        self.class.references_in(text) do |match, id, name|
-          params = label_params(id, name)
-
-          if label = project.labels.find_by(params)
-            url = url_for_label(project, label)
-            klass = reference_class(:label)
-            data = data_attribute(
-              original: link_text || match,
-              project: project.id,
-              label: label.id
-            )
+      def self.referenced_by(node)
+        { label: LazyReference.new(Label, node.attr("data-label")) }
+      end
 
-            text = link_text || render_colored_label(label)
+      def references_in(text, pattern = Label.reference_pattern)
+        text.gsub(pattern) do |match|
+          project = project_from_ref($~[:project])
+          params = label_params($~[:label_id].to_i, $~[:label_name])
+          label = project.labels.find_by(params)
 
-            %(<a href="#{url}" #{data}
-                 class="#{klass}">#{escape_once(text)}</a>)
+          if label
+            yield match, label.id, $~[:project], $~
           else
             match
           end
         end
       end
 
-      def url_for_label(project, label)
+      def url_for_object(label, project)
         h = Gitlab::Application.routes.url_helpers
-        h.namespace_project_issues_url( project.namespace, project, label_name: label.name,
+        h.namespace_project_issues_url(project.namespace, project, label_name: label.name,
                                                                    only_path:  context[:only_path])
       end
 
-      def render_colored_label(label)
-        LabelsHelper.render_colored_label(label)
+      def object_link_text(object, _matches)
+        LabelsHelper.render_colored_label(object)
       end
 
       # Parameters to pass to `Label.find_by` based on the given arguments

spec/lib/banzai/filter/label_reference_filter_spec.rb

@@ -176,4 +176,23 @@ describe Banzai::Filter::LabelReferenceFilter, lib: true do
       expect(result[:references][:label]).to eq [label]
     end
   end
+
+  describe 'cross project label references' do
+    let(:another_project)  { create(:empty_project, :public) }
+    let(:label) { create(:label, project: another_project, color: '#00ff00') }
+    let(:reference) { label.to_reference(project) }
+
+    let!(:result) { reference_filter("See #{reference}") }
+
+    it 'points to referenced project issues page' do
+      expect(result.css('a').first.attr('href'))
+        .to eq urls.namespace_project_issues_url(another_project.namespace,
+                                                 another_project,
+                                                 label_name: label.name)
+    end
+
+    it 'has valid color' do
+      expect(result.css('a span').first.attr('style')).to match /background-color: #00ff00/
+    end
+  end
 end