Change language detection to include hashtags as words (#11341)

app/lib/language_detector.rb

@@ -69,7 +69,7 @@ class LanguageDetector
     new_text = remove_html(text)
     new_text.gsub!(FetchLinkCardService::URL_PATTERN, '')
     new_text.gsub!(Account::MENTION_RE, '')
-    new_text.gsub!(Tag::HASHTAG_RE, '')
+    new_text.gsub!(Tag::HASHTAG_RE) { |string| string.gsub(/[#_]/, '#' => '', '_' => ' ').gsub(/[a-z][A-Z]|[a-zA-Z][\d]/) { |s| s.insert(1, ' ') }.downcase }
     new_text.gsub!(/:#{CustomEmoji::SHORTCODE_RE_FRAGMENT}:/, '')
     new_text.gsub!(/\s+/, ' ')
     new_text

spec/lib/language_detector_spec.rb

@@ -32,11 +32,11 @@ describe LanguageDetector do
       expect(result).to eq 'Our website is and also'
     end
 
-    it 'strips #hashtags from strings before detection' do
-      string = 'Hey look at all the #animals and #fish'
+    it 'converts #hashtags back to normal text before detection' do
+      string = 'Hey look at all the #animals and #FishAndChips'
 
       result = described_class.instance.send(:prepare_text, string)
-      expect(result).to eq 'Hey look at all the and'
+      expect(result).to eq 'Hey look at all the animals and fish and chips'
     end
   end