FEATURE: Correctly convert topic title to uppercase and lowercase for Turkish default locale (#13115)

lib/text_cleaner.rb

@@ -20,7 +20,8 @@ class TextCleaner
       remove_extraneous_space: SiteSetting.title_prettify && SiteSetting.title_remove_extraneous_space,
       fixes_interior_spaces: true,
       strip_whitespaces: true,
-      strip_zero_width_spaces: true
+      strip_zero_width_spaces: true,
+      case_option: SiteSetting.default_locale == "tr_TR" ? :turkic : nil
     }
   end
 
@@ -33,27 +34,37 @@ class TextCleaner
 
     # Remove invalid byte sequences
     text.scrub!("")
+
     # Replace !!!!! with a single !
     text.gsub!(/!+/, '!') if opts[:deduplicate_exclamation_marks]
+
     # Replace ????? with a single ?
     text.gsub!(/\?+/, '?') if opts[:deduplicate_question_marks]
+
     # Replace all-caps text with regular case letters
-    text = text.mb_chars.downcase.to_s if opts[:replace_all_upper_case] && (text == text.mb_chars.upcase)
+    text = downcase(text.mb_chars, opts).to_s if opts[:replace_all_upper_case] && (text == upcase(text.mb_chars, opts))
+
     # Capitalize first letter, but only when entire first word is lowercase
     first, rest = text.split(' ', 2)
-    if first && opts[:capitalize_first_letter] && first == first.mb_chars.downcase
-      text = +"#{first.mb_chars.capitalize}#{rest ? ' ' + rest : ''}"
+    if first && opts[:capitalize_first_letter] && first == downcase(first.mb_chars, opts)
+      text = +"#{capitalize(first.mb_chars, opts)}#{rest ? ' ' + rest : ''}"
     end
+
     # Remove unnecessary periods at the end
     text.sub!(/([^.])\.+(\s*)\z/, '\1\2') if opts[:remove_all_periods_from_the_end]
+
     # Remove extraneous space before the end punctuation
     text.sub!(/\s+([!?]\s*)\z/, '\1') if opts[:remove_extraneous_space]
+
     # Fixes interior spaces
     text.gsub!(/ +/, ' ') if opts[:fixes_interior_spaces]
+
     # Normalize whitespaces
     text = normalize_whitespaces(text)
+
     # Strip whitespaces
     text.strip! if opts[:strip_whitespaces]
+
     # Strip zero width spaces
     text.gsub!(/\u200b/, '') if opts[:strip_zero_width_spaces]
 
@@ -66,4 +77,15 @@ class TextCleaner
     text&.gsub(@@whitespaces_regexp, ' ')
   end
 
+  def self.downcase(text, opts)
+    opts[:case_option] ? text.downcase(opts[:case_option]) : text.downcase
+  end
+
+  def self.upcase(text, opts)
+    opts[:case_option] ? text.upcase(opts[:case_option]) : text.upcase
+  end
+
+  def self.capitalize(text, opts)
+    opts[:case_option] ? text.capitalize(opts[:case_option]) : text.capitalize
+  end
 end

spec/components/text_cleaner_spec.rb

@@ -215,6 +215,14 @@ describe TextCleaner do
         expect(TextCleaner.clean_title("épico encontro")).to eq("Épico encontro")
       end
 
+      it "correctly cleans Turkish characters" do
+        expect(TextCleaner.clean_title("GIDA")).to eq("Gida")
+        expect(TextCleaner.clean_title("istanbul")).to eq("Istanbul")
+
+        SiteSetting.default_locale = "tr_TR"
+        expect(TextCleaner.clean_title("GIDA")).to eq("Gıda")
+        expect(TextCleaner.clean_title("istanbul")).to eq("İstanbul")
+      end
     end
 
   end