Match Rinku's behaviour for closing punctuation in links41719-mr-title-fix

Rinku 2.0.0 (the version we use) will remove the last character of a link if
it's a closing part of a punctuation pair (different types of parentheses and
quotes), unless both of the below are true:

1. The matching pair has different start and end characters.
2. There are equal numbers of both in the matched string (they don't have to be
   balanced).

1 files changed, 35 insertions, 15 deletions

diff --git a/lib/banzai/filter/autolink_filter.rb b/lib/banzai/filter/autolink_filter.rb
index c4990637971..75b64ae9af2 100644
--- a/lib/banzai/filter/autolink_filter.rb
+++ b/lib/banzai/filter/autolink_filter.rb
@@ -25,7 +25,7 @@ module Banzai
       # period or comma for punctuation without those characters being included
       # in the generated link.
       #
-      # Rubular: http://rubular.com/r/cxjPyZc7Sb
+      # Rubular: http://rubular.com/r/JzPhi6DCZp
       LINK_PATTERN = %r{([a-z][a-z0-9\+\.-]+://[^\s>]+)(?<!,|\.)}
 
       # Text matching LINK_PATTERN inside these elements will not be linked
@@ -37,23 +37,17 @@ module Banzai
         and contains(., '://')
       ]).freeze
 
+      PUNCTUATION_PAIRS = {
+        "'" => "'",
+        '"' => '"',
+        ')' => '(',
+        ']' => '[',
+        '}' => '{'
+      }.freeze
+
       def call
         return doc if context[:autolink] == false
 
-        text_parse
-      end
-
-      private
-
-      # Return true if any of the UNSAFE_PROTOCOLS strings are included in the URI scheme
-      def contains_unsafe?(scheme)
-        return false unless scheme
-
-        scheme = scheme.strip.downcase
-        Banzai::Filter::SanitizationFilter::UNSAFE_PROTOCOLS.any? { |protocol| scheme.include?(protocol) }
-      end
-
-      def text_parse
         doc.xpath(TEXT_QUERY).each do |node|
           content = node.to_html
 
@@ -69,6 +63,16 @@ module Banzai
         doc
       end
 
+      private
+
+      # Return true if any of the UNSAFE_PROTOCOLS strings are included in the URI scheme
+      def contains_unsafe?(scheme)
+        return false unless scheme
+
+        scheme = scheme.strip.downcase
+        Banzai::Filter::SanitizationFilter::UNSAFE_PROTOCOLS.any? { |protocol| scheme.include?(protocol) }
+      end
+
       def autolink_match(match)
         # start by stripping out dangerous links
         begin
@@ -84,6 +88,22 @@ module Banzai
         match.gsub!(/((?:&[\w#]+;)+)\z/, '')
         dropped = ($1 || '').html_safe
 
+        # To match the behaviour of Rinku, if the matched link ends with a
+        # closing part of a matched pair of punctuation, we remove that trailing
+        # character unless there are an equal number of closing and opening
+        # characters in the link.
+        if match.end_with?(*PUNCTUATION_PAIRS.keys)
+          close_character = match[-1]
+          close_count = match.count(close_character)
+          open_character = PUNCTUATION_PAIRS[close_character]
+          open_count = match.count(open_character)
+
+          if open_count != close_count || open_character == close_character
+            dropped += close_character
+            match = match[0..-2]
+          end
+        end
+
         options = link_options.merge(href: match)
         content_tag(:a, match.html_safe, options) + dropped
       end