Support tsearch followed by operator (<->)

lib/pg_search/features/tsearch.rb

@@ -7,7 +7,7 @@ module PgSearch
   module Features
     class TSearch < Feature # rubocop:disable Metrics/ClassLength
       def self.valid_options
-        super + %i[dictionary prefix negation any_word normalization tsvector_column highlight]
+        super + %i[dictionary prefix negation any_word followed_by normalization tsvector_column highlight]
       end
 
       def conditions
@@ -133,7 +133,15 @@ def tsquery
 
         query_terms = query.split(" ").compact
         tsquery_terms = query_terms.map { |term| tsquery_for_term(term) }
-        tsquery_terms.join(options[:any_word] ? ' || ' : ' && ')
+        join_op =
+          if options[:any_word]
+            ' || '
+          elsif options[:followed_by]
+            ' <-> '
+          else
+            ' && '
+          end
+        tsquery_terms.join(join_op)
       end
 
       def tsdocument

spec/integration/pg_search_spec.rb

@@ -785,6 +785,28 @@
         end
       end
 
+      context "searching followed_by option" do
+        before do
+          ModelWithPgSearch.pg_search_scope :search_title_with_followed_by,
+                                            against: :title,
+                                            using: {
+                                              tsearch: { followed_by: true }
+                                            }
+        end
+
+        it "returns all results containing word followed by another word in their title" do
+          numbers = %w[one two three four].each_cons(2) { |word_sequence| ModelWithPgSearch.create!(title: word_sequence.join(' ')) }
+
+          results = ModelWithPgSearch.search_title_with_followed_by("one two")
+
+          expect(results.map(&:title)).to eq(["one two"])
+
+          results = ModelWithPgSearch.search_title_with_followed_by("one three")
+
+          expect(results.map(&:title)).to eq([])
+        end
+      end
+
       context "with :negation" do
         before do
           ModelWithPgSearch.pg_search_scope :search_with_negation,