Implementing special GitLab markdown reference for milestones

Using the syntax proposed in #13829 [project_reference]%(milestone_id | milestone_name)
to get a link to the referred milestone.

app/models/milestone.rb

@@ -74,8 +74,22 @@ class Milestone < ActiveRecord::Base
     end
   end
 
+  def self.reference_prefix
+    '%'
+  end
+
   def self.reference_pattern
-    nil
+    %r{
+      (#{Project.reference_pattern})?
+      #{Regexp.escape(reference_prefix)}
+      (?:
+        (?<milestone_id>\d+) | # Integer-based milestone ID, or
+        (?<milestone_name>
+          [A-Za-z0-9_-]+ | # String-based single-word milestone title, or
+          "[^"]+"       # String-based multi-word milestone surrounded in quotes
+        )
+      )
+    }x
   end
 
   def self.link_reference_pattern
@@ -86,13 +100,15 @@ class Milestone < ActiveRecord::Base
     self.where('due_date > ?', Time.now).reorder(due_date: :asc).first
   end
 
-  def to_reference(from_project = nil)
-    escaped_title = self.title.gsub("]", "\\]")
+  def to_reference(from_project = nil, format: :id)
+    format_reference = milestone_format_reference(format)
+    reference = "#{self.class.reference_prefix}#{format_reference}"
 
-    h = Gitlab::Routing.url_helpers
-    url = h.namespace_project_milestone_url(self.project.namespace, self.project, self)
-
-    "[#{escaped_title}](#{url})"
+    if cross_project_reference?(from_project)
+      project.to_reference + reference
+    else
+      reference
+    end
   end
 
   def reference_link_text(from_project = nil)
@@ -160,4 +176,16 @@ class Milestone < ActiveRecord::Base
     issues.where(id: ids).
       update_all(["position = CASE #{conditions} ELSE position END", *pairs])
   end
+
+  private
+
+  def milestone_format_reference(format = :id)
+    raise StandardError, 'Unknown format' unless [:id, :name].include?(format)
+
+    if format == :name && !name.include?('"')
+      %("#{name}")
+    else
+      id
+    end
+  end
 end

lib/banzai/filter/milestone_reference_filter.rb

@@ -7,14 +7,36 @@ module Banzai
       end
 
       def find_object(project, id)
-        project.milestones.find_by(iid: id)
+        project.milestones.find(id)
       end
 
-      def url_for_object(issue, project)
+      def references_in(text, pattern = Milestone.reference_pattern)
+        text.gsub(pattern) do |match|
+          project = project_from_ref($~[:project])
+          params = milestone_params($~[:milestone_id].to_i, $~[:milestone_name])
+          milestone = project.milestones.find_by(params)
+
+          if milestone
+            yield match, milestone.id, $~[:project], $~
+          else
+            match
+          end
+        end
+      end
+
+      def url_for_object(milestone, project)
         h = Gitlab::Routing.url_helpers
         h.namespace_project_milestone_url(project.namespace, project, milestone,
                                         only_path: context[:only_path])
       end
+
+      def milestone_params(id, name)
+        if name
+          { name: name.tr('"', '') }
+        else
+          { id: id }
+        end
+      end
     end
   end
 end

spec/fixtures/markdown.md.erb

@@ -216,10 +216,13 @@ References should be parseable even inside _<%= merge_request.to_reference %>_ e
 
 #### MilestoneReferenceFilter
 
-- Milestone: <%= milestone.to_reference %>
+- Milestone by ID: <%= simple_milestone.to_reference %>
+- Milestone by name: <%= Milestone.reference_prefix %><%= simple_milestone.name %>
+- Milestone by name in quotes: <%= milestone.to_reference(format: :name) %>
 - Milestone in another project: <%= xmilestone.to_reference(project) %>
-- Ignored in code: `<%= milestone.to_reference %>`
-- Link to milestone by URL: [Milestone](<%= urls.namespace_project_milestone_url(milestone.project.namespace, milestone.project, milestone) %>)
+- Ignored in code: `<%= simple_milestone.to_reference %>`
+- Ignored in links: [Link to <%= simple_milestone.to_reference %>](#milestone-link)
+- Link to milestone by URL: [Milestone](<%= milestone.to_reference %>)
 
 ### Task Lists
 

spec/support/markdown_feature.rb

@@ -63,8 +63,12 @@ class MarkdownFeature
     @label ||= create(:label, name: 'awaiting feedback', project: project)
   end
 
+  def simple_milestone
+    @simple_milestone ||= create(:milestone, name: 'gfm-milestone', project: project)
+  end
+
   def milestone
-    @milestone ||= create(:milestone, project: project)
+    @milestone ||= create(:milestone, name: 'next goal', project: project)
   end
 
   # Cross-references -----------------------------------------------------------

spec/support/matchers/markdown_matchers.rb

@@ -154,7 +154,7 @@ module MarkdownMatchers
     set_default_markdown_messages
 
     match do |actual|
-      expect(actual).to have_selector('a.gfm.gfm-milestone', count: 3)
+      expect(actual).to have_selector('a.gfm.gfm-milestone', count: 5)
     end
   end