Optimize String#parameterize

It can use a codepath where it doesn't have to do regex stuff:

```rb
require "benchmark/ips"
require "active_support"
require "active_support/inflector/transliterate"

CASES = [
  "Donald E. Knuth"                    ,
  "Random text with *(bad)* characters",
  "With-some-dashes"                   ,
  "Retain_underscore"                  ,
  "Trailing bad characters!@#"         ,
  "!@#Leading bad characters"          ,
  "Squeeze   separators"               ,
  "Test with + sign"                   ,
  "Test with malformed utf8 \251"      ,
]

def parameterize_old(string, separator: "-", preserve_case: false, locale: nil)
  # Replace accented chars with their ASCII equivalents.
  parameterized_string = ActiveSupport::Inflector.transliterate(string)

  # 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_duplicate_separator, separator)
    # Remove leading/trailing separator.
    parameterized_string.gsub!(re_leading_trailing_separator, "")
  end

  parameterized_string.downcase! unless preserve_case
  parameterized_string
end

def parameterize_new(string, separator: "-", preserve_case: false, locale: nil)
  # Replace accented chars with their ASCII equivalents.
  parameterized_string = ActiveSupport::Inflector.transliterate(string)

  # Turn unwanted chars into the separator.
  parameterized_string.gsub!(/[^a-z0-9\-_]+/i, separator)

  unless separator.nil? || separator.empty?
    # No more than one of the separator in a row.
    if separator.length == 1
      parameterized_string.squeeze!(separator)
    else
      re_sep = Regexp.escape(separator)
      parameterized_string.gsub!(/#{re_sep}{2,}/, separator)
    end
    # Remove leading/trailing separator.
    parameterized_string.delete_prefix!(separator)
    parameterized_string.delete_suffix!(separator)
  end

  parameterized_string.downcase! unless preserve_case
  parameterized_string
end

puts "DEFAULT SEPARATOR"

Benchmark.ips do |x|
  x.report("old") do
    CASES.each { parameterize_old(_1) }
  end

  x.report("new") do
    CASES.each { parameterize_new(_1) }
  end
  x.compare!
end

puts "OTHER SEPARATOR LENGTH ONE"

Benchmark.ips do |x|
  x.report("old") do
    CASES.each { parameterize_old(_1, separator: "_") }
  end

  x.report("new") do
    CASES.each { parameterize_new(_1, separator: "_") }
  end
  x.compare!
end

puts "OTHER SEPARATOR LENGTH TWO"

Benchmark.ips do |x|
  x.report("old") do
    CASES.each { parameterize_old(_1, separator: "__") }
  end

  x.report("new") do
    CASES.each { parameterize_new(_1, separator: "__") }
  end
  x.compare!
end
```

```
$ ruby test.rb
DEFAULT SEPARATOR
ruby 3.4.2 (2025-02-15 revision d2930f8e7a) +PRISM [x86_64-linux]
Warming up --------------------------------------
                 old     2.733k i/100ms
                 new     3.278k i/100ms
Calculating -------------------------------------
                 old     27.335k (± 1.3%) i/s   (36.58 μs/i) -    139.383k in   5.099871s
                 new     32.694k (± 0.8%) i/s   (30.59 μs/i) -    163.900k in   5.013461s

Comparison:
                 new:    32694.3 i/s
                 old:    27335.4 i/s - 1.20x  slower

OTHER SEPARATOR LENGTH ONE
ruby 3.4.2 (2025-02-15 revision d2930f8e7a) +PRISM [x86_64-linux]
Warming up --------------------------------------
                 old     1.295k i/100ms
                 new     3.273k i/100ms
Calculating -------------------------------------
                 old     12.901k (± 1.9%) i/s   (77.51 μs/i) -     64.750k in   5.020950s
                 new     32.656k (± 1.4%) i/s   (30.62 μs/i) -    163.650k in   5.012471s

Comparison:
                 new:    32655.6 i/s
                 old:    12901.1 i/s - 2.53x  slower

OTHER SEPARATOR LENGTH TWO
ruby 3.4.2 (2025-02-15 revision d2930f8e7a) +PRISM [x86_64-linux]
Warming up --------------------------------------
                 old     1.189k i/100ms
                 new     1.888k i/100ms
Calculating -------------------------------------
                 old     11.908k (± 0.4%) i/s   (83.98 μs/i) -     60.639k in   5.092317s
                 new     18.813k (± 1.0%) i/s   (53.16 μs/i) -     94.400k in   5.018446s

Comparison:
                 new:    18812.7 i/s
                 old:    11908.1 i/s - 1.58x  slower

```

Author: Earlopain

activesupport/lib/active_support/inflector/transliterate.rb

@@ -128,18 +128,16 @@ def parameterize(string, separator: "-", preserve_case: false, locale: nil)
       parameterized_string.gsub!(/[^a-z0-9\-_]+/i, separator)
 
       unless separator.nil? || separator.empty?
-        if separator == "-"
-          re_duplicate_separator        = /-{2,}/
-          re_leading_trailing_separator = /^-|-$/i
+        # No more than one of the separator in a row.
+        if separator.length == 1
+          parameterized_string.squeeze!(separator)
         else
           re_sep = Regexp.escape(separator)
-          re_duplicate_separator        = /#{re_sep}{2,}/
-          re_leading_trailing_separator = /^#{re_sep}|#{re_sep}$/i
+          parameterized_string.gsub!(/#{re_sep}{2,}/, separator)
         end
-        # No more than one of the separator in a row.
-        parameterized_string.gsub!(re_duplicate_separator, separator)
         # Remove leading/trailing separator.
-        parameterized_string.gsub!(re_leading_trailing_separator, "")
+        parameterized_string.delete_prefix!(separator)
+        parameterized_string.delete_suffix!(separator)
       end
 
       parameterized_string.downcase! unless preserve_case