@mention provides a context variable for overriding username pattern

* This allows for easier customization of the usernam mention pattern regex

lib/html/pipeline/@mention_filter.rb

@@ -11,6 +11,8 @@ class Pipeline
     #               mention.
     #   :info_url - Used to link to "more info" when someone mentions @mention
     #               or @mentioned.
+    #   :username_pattern - Used to provide a custom regular expression to
+    #                       identify usernames
     #
     class MentionFilter < Filter
       # Public: Find user @mentions in text.  See
@@ -27,25 +29,31 @@ class MentionFilter < Filter
       # the original text.
       #
       # Returns a String replaced with the return of the block.
-      def self.mentioned_logins_in(text)
-        text.gsub MentionPattern do |match|
+      def self.mentioned_logins_in(text, username_pattern=UsernamePattern)
+        text.gsub MentionPatterns[username_pattern] do |match|
           login = $1
           yield match, login, MentionLogins.include?(login.downcase)
         end
       end
 
-      # Pattern used to extract @mentions from text.
-      MentionPattern = /
-        (?:^|\W)                   # beginning of string or non-word char
-        @((?>[a-z0-9][a-z0-9-]*))  # @username
-        (?!\/)                     # without a trailing slash
-        (?=
-          \.+[ \t\W]|              # dots followed by space or non-word character
-          \.+$|                    # dots at end of line
-          [^0-9a-zA-Z_.]|          # non-word character except dot
-          $                        # end of line
-        )
-      /ix
+      # Hash that contains all of the mention patterns used by the pipeline
+      MentionPatterns = Hash.new do |hash, key|
+        hash[key] = /
+          (?:^|\W)                    # beginning of string or non-word char
+          @((?>#{key}))  # @username
+          (?!\/)                      # without a trailing slash
+          (?=
+            \.+[ \t\W]|               # dots followed by space or non-word character
+            \.+$|                     # dots at end of line
+            [^0-9a-zA-Z_.]|           # non-word character except dot
+            $                         # end of line
+          )
+        /ix
+      end
+
+      # Default pattern used to extract usernames from text. The value can be
+      # overriden by providing the username_pattern variable in the context.
+      UsernamePattern = /[a-z0-9][a-z0-9-]*/
 
       # List of username logins that, when mentioned, link to the blog post
       # about @mentions instead of triggering a real mention.
@@ -66,7 +74,7 @@ def call
           content = node.to_html
           next if !content.include?('@')
           next if has_ancestor?(node, IGNORE_PARENTS)
-          html = mention_link_filter(content, base_url, info_url)
+          html = mention_link_filter(content, base_url, info_url, username_pattern)
           next if html == content
           node.replace(html)
         end
@@ -79,18 +87,24 @@ def info_url
         context[:info_url] || nil
       end
 
+      def username_pattern
+        context[:username_pattern] || UsernamePattern
+      end
+
       # Replace user @mentions in text with links to the mentioned user's
       # profile page.
       #
       # text      - String text to replace @mention usernames in.
       # base_url  - The base URL used to construct user profile URLs.
       # info_url  - The "more info" URL used to link to more info on @mentions.
       #             If nil we don't link @mention or @mentioned.
+      # username_pattern  - Regular expression used to identify usernames in
+      #                     text
       #
       # Returns a string with @mentions replaced with links. All links have a
       # 'user-mention' class name attached for styling.
-      def mention_link_filter(text, base_url='/', info_url=nil)
-        self.class.mentioned_logins_in(text) do |match, login, is_mentioned|
+      def mention_link_filter(text, base_url='/', info_url=nil, username_pattern)
+        self.class.mentioned_logins_in(text, username_pattern) do |match, login, is_mentioned|
           link =
             if is_mentioned
               link_to_mention_info(login, info_url)

test/html/pipeline/mention_filter_test.rb

@@ -1,8 +1,8 @@
 require "test_helper"
 
 class HTML::Pipeline::MentionFilterTest < Minitest::Test
-  def filter(html, base_url='/', info_url=nil)
-    HTML::Pipeline::MentionFilter.call(html, :base_url => base_url, :info_url => info_url)
+  def filter(html, base_url='/', info_url=nil, username_pattern=nil)
+    HTML::Pipeline::MentionFilter.call(html, :base_url => base_url, :info_url => info_url, :username_pattern => username_pattern)
   end
 
   def test_filtering_a_documentfragment
@@ -158,4 +158,28 @@ def test_mention_at_end_of_parenthetical_sentence
     @body = "(We're talking 'bout @ymendel.)"
     assert_equal %w[ymendel], mentioned_usernames
   end
+
+  def test_username_pattern_can_be_customized
+    body = "<p>@_abc: test.</p>"
+    doc  = Nokogiri::HTML::DocumentFragment.parse(body)
+
+    res  = filter(doc, '/', nil, /(_[a-z]{3})/)
+
+    link = "<a href=\"/_abc\" class=\"user-mention\">@_abc</a>"
+    assert_equal "<p>#{link}: test.</p>",
+      res.to_html
+  end
+
+  def test_filter_does_not_create_a_new_object_for_default_username_pattern
+    body = "<div>@test</div>"
+    doc = Nokogiri::HTML::DocumentFragment.parse(body)
+
+    filter(doc.clone, '/', nil)
+    pattern_count = HTML::Pipeline::MentionFilter::MentionPatterns.length
+    filter(doc.clone, '/', nil)
+
+    assert_equal pattern_count, HTML::Pipeline::MentionFilter::MentionPatterns.length
+    filter(doc.clone, '/', nil, /test/)
+    assert_equal pattern_count + 1, HTML::Pipeline::MentionFilter::MentionPatterns.length
+  end
 end