1 files changed, 48 insertions, 17 deletions

diff --git a/activesupport/lib/active_support/inflector/transliterate.rb b/activesupport/lib/active_support/inflector/transliterate.rb
index edea142e82..0d2a17970f 100644
--- a/activesupport/lib/active_support/inflector/transliterate.rb
+++ b/activesupport/lib/active_support/inflector/transliterate.rb
@@ -1,10 +1,10 @@
-# encoding: utf-8
-require 'active_support/core_ext/string/multibyte'
-require 'active_support/i18n'
+# frozen_string_literal: true
+
+require "active_support/core_ext/string/multibyte"
+require "active_support/i18n"
 
 module ActiveSupport
   module Inflector
-
     # Replaces non-ASCII characters with an ASCII approximation, or if none
     # exists, a replacement character which defaults to "?".
     #
@@ -59,29 +59,60 @@ module ActiveSupport
     #   transliterate('Jürgen')
     #   # => "Juergen"
     def transliterate(string, replacement = "?")
-      I18n.transliterate(ActiveSupport::Multibyte::Unicode.normalize(
-        ActiveSupport::Multibyte::Unicode.tidy_bytes(string), :c),
-          :replacement => replacement)
+      raise ArgumentError, "Can only transliterate strings. Received #{string.class.name}" unless string.is_a?(String)
+
+      I18n.transliterate(
+        ActiveSupport::Multibyte::Unicode.tidy_bytes(string).unicode_normalize(:nfc),
+        replacement: replacement
+      )
     end
 
     # Replaces special characters in a string so that it may be used as part of
     # a 'pretty' URL.
     #
     #   parameterize("Donald E. Knuth") # => "donald-e-knuth"
-    #   parameterize("^trés|Jolie-- ")  # => "tres-jolie"
-    def parameterize(string, sep = '-')
-      # replace accented chars with their ascii equivalents
+    #   parameterize("^très|Jolie-- ")  # => "tres-jolie"
+    #
+    # To use a custom separator, override the +separator+ argument.
+    #
+    #  parameterize("Donald E. Knuth", separator: '_') # => "donald_e_knuth"
+    #  parameterize("^très|Jolie__ ", separator: '_')  # => "tres_jolie"
+    #
+    # To preserve the case of the characters in a string, use the +preserve_case+ argument.
+    #
+    #   parameterize("Donald E. Knuth", preserve_case: true) # => "Donald-E-Knuth"
+    #   parameterize("^très|Jolie-- ", preserve_case: true) # => "tres-Jolie"
+    #
+    # It preserves dashes and underscores unless they are used as separators:
+    #
+    #  parameterize("^très|Jolie__ ")                 # => "tres-jolie__"
+    #  parameterize("^très|Jolie-- ", separator: "_") # => "tres_jolie--"
+    #  parameterize("^très_Jolie-- ", separator: ".") # => "tres_jolie--"
+    #
+    def parameterize(string, separator: "-", preserve_case: false)
+      # Replace accented chars with their ASCII equivalents.
       parameterized_string = transliterate(string)
-      # Turn unwanted chars into the separator
-      parameterized_string.gsub!(/[^a-z0-9\-_]+/i, sep)
-      unless sep.nil? || sep.empty?
-        re_sep = Regexp.escape(sep)
+
+      # Turn unwanted chars into the separator.
+      parameterized_string.gsub!(/[^a-z0-9\-_]+/i, separator)
+
+      unless separator.nil? || separator.empty?
+        if separator == "-"
+          re_duplicate_separator        = /-{2,}/
+          re_leading_trailing_separator = /^-|-$/i
+        else
+          re_sep = Regexp.escape(separator)
+          re_duplicate_separator        = /#{re_sep}{2,}/
+          re_leading_trailing_separator = /^#{re_sep}|#{re_sep}$/i
+        end
         # No more than one of the separator in a row.
-        parameterized_string.gsub!(/#{re_sep}{2,}/, sep)
+        parameterized_string.gsub!(re_duplicate_separator, separator)
         # Remove leading/trailing separator.
-        parameterized_string.gsub!(/^#{re_sep}|#{re_sep}$/i, '')
+        parameterized_string.gsub!(re_leading_trailing_separator, "")
       end
-      parameterized_string.downcase
+
+      parameterized_string.downcase! unless preserve_case
+      parameterized_string
     end
   end
 end