Add `CustomFilterKeyword#to_regex` method (#28893)

app/models/custom_filter.rb

@@ -68,16 +68,7 @@ class CustomFilter < ApplicationRecord
 
       scope = CustomFilterKeyword.includes(:custom_filter).where(custom_filter: { account_id: account_id }).where(Arel.sql('expires_at IS NULL OR expires_at > NOW()'))
       scope.to_a.group_by(&:custom_filter).each do |filter, keywords|
-        keywords.map! do |keyword|
-          if keyword.whole_word
-            sb = /\A[[:word:]]/.match?(keyword.keyword) ? '\b' : ''
-            eb = /[[:word:]]\z/.match?(keyword.keyword) ? '\b' : ''
-
-            /(?mix:#{sb}#{Regexp.escape(keyword.keyword)}#{eb})/
-          else
-            /#{Regexp.escape(keyword.keyword)}/i
-          end
-        end
+        keywords.map!(&:to_regex)
 
         filters_hash[filter.id] = { keywords: Regexp.union(keywords), filter: filter }
       end.to_h

app/models/custom_filter_keyword.rb

@@ -23,8 +23,24 @@ class CustomFilterKeyword < ApplicationRecord
   before_destroy :prepare_cache_invalidation!
   after_commit :invalidate_cache!
 
+  def to_regex
+    if whole_word?
+      /(?mix:#{to_regex_sb}#{Regexp.escape(keyword)}#{to_regex_eb})/
+    else
+      /#{Regexp.escape(keyword)}/i
+    end
+  end
+
   private
 
+  def to_regex_sb
+    /\A[[:word:]]/.match?(keyword) ? '\b' : ''
+  end
+
+  def to_regex_eb
+    /[[:word:]]\z/.match?(keyword) ? '\b' : ''
+  end
+
   def prepare_cache_invalidation!
     custom_filter.prepare_cache_invalidation!
   end

spec/models/custom_filter_keyword_spec.rb

@@ -0,0 +1,35 @@
+# frozen_string_literal: true
+
+require 'rails_helper'
+
+RSpec.describe CustomFilterKeyword do
+  describe '#to_regex' do
+    context 'when whole_word is true' do
+      it 'builds a regex with boundaries and the keyword' do
+        keyword = described_class.new(whole_word: true, keyword: 'test')
+
+        expect(keyword.to_regex).to eq(/(?mix:\b#{Regexp.escape(keyword.keyword)}\b)/)
+      end
+
+      it 'builds a regex with starting boundary and the keyword when end with non-word' do
+        keyword = described_class.new(whole_word: true, keyword: 'test#')
+
+        expect(keyword.to_regex).to eq(/(?mix:\btest\#)/)
+      end
+
+      it 'builds a regex with end boundary and the keyword when start with non-word' do
+        keyword = described_class.new(whole_word: true, keyword: '#test')
+
+        expect(keyword.to_regex).to eq(/(?mix:\#test\b)/)
+      end
+    end
+
+    context 'when whole_word is false' do
+      it 'builds a regex with the keyword' do
+        keyword = described_class.new(whole_word: false, keyword: 'test')
+
+        expect(keyword.to_regex).to eq(/test/i)
+      end
+    end
+  end
+end