Use blank? check instead of key? check

This allows us to prevent an extra string allocation when there is a rel
argument and performs better/within error of the key check for other
scenarios such as passing in rel: nil

```ruby
begin
  require "bundler/inline"
rescue LoadError => e
  $stderr.puts "Bundler version 1.10 or later is required. Please update
                your Bundler"
  raise e
end

gemfile(true) do
  source "https://rubygems.org"

  gem "benchmark-ips"
  gem "rails"
end

def allocate_count
  GC.disable
  before = ObjectSpace.count_objects
  yield
  after = ObjectSpace.count_objects
  after.each { |k,v| after[k] = v - before[k] }
  after[:T_HASH] -= 1 # probe effect - we created the before hash.
  GC.enable
  result = after.reject { |k,v| v == 0 }
  GC.start
  result
end

@hash = {}

def master_version
  "#{@hash["rel"]} nofollow".lstrip
end

def key_version
  if @hash.key?("rel")
    "#{@hash["rel"]} nofollow".lstrip
  else
    "nofollow"
  end
end

def present_version
  if @hash["rel"].present?
    "#{@hash["rel"]} nofollow"
  else
    "nofollow".freeze
  end
end

def nil_version
  if @hash["rel"].nil?
    "nofollow".freeze
  else
    "#{@hash["rel"]} nofollow"
  end
end

def blank_version
  if @hash["rel"].blank?
    "nofollow".freeze
  else
    "#{@hash["rel"]} nofollow"
  end
end

def test
  puts "master_version"
  puts allocate_count { 1000.times { master_version } }
  puts "key_version"
  puts allocate_count { 1000.times { key_version } }
  puts "present_version"
  puts allocate_count { 1000.times { present_version } }
  puts "nil_version"
  puts allocate_count { 1000.times { nil_version } }
  puts "blank_version"
  puts allocate_count { 1000.times { blank_version } }

  Benchmark.ips do |x|
    x.report("master_version")  { master_version }
    x.report("key_version")     { key_version }
    x.report("present_version") { present_version }
    x.report("nil_version")     { nil_version }
    x.report("blank_version")     { blank_version }
    x.compare!
  end
end

puts 'no rel key'

test

puts 'rel key with real stuff'

@hash['rel'] = 'hi'.freeze

test

puts 'rel key with nil'

@hash['rel'] = nil

test

puts 'rel key with ""'

@hash['rel'] = ""

test
```

```
no rel key
master_version
{:FREE=>-2818, :T_STRING=>3052}
key_version
{:FREE=>-1}
present_version
{:FREE=>-1}
nil_version
{:FREE=>-1}
blank_version
{:FREE=>-1}
Warming up --------------------------------------
      master_version   124.677k i/100ms
         key_version   227.992k i/100ms
     present_version   208.068k i/100ms
         nil_version   235.272k i/100ms
       blank_version   176.274k i/100ms
Calculating -------------------------------------
      master_version      1.968M (±10.8%) i/s -      9.725M in   5.010763s
         key_version      7.734M (±11.2%) i/s -     38.075M in   5.001613s
     present_version      5.688M (±11.4%) i/s -     28.089M in   5.019560s
         nil_version      6.965M (±10.2%) i/s -     34.585M in   5.024806s
       blank_version      6.139M (±18.7%) i/s -     29.085M in   5.010919s

Comparison:
         key_version:  7734058.3 i/s
         nil_version:  6965050.2 i/s - same-ish: difference falls within error
       blank_version:  6138744.3 i/s - same-ish: difference falls within error
     present_version:  5688248.4 i/s - 1.36x  slower
      master_version:  1967932.3 i/s - 3.93x  slower

rel key with real stuff
master_version
{:FREE=>-2001, :T_STRING=>2000}
key_version
{:FREE=>-2001, :T_STRING=>2000}
present_version
{:FREE=>-1001, :T_STRING=>1000}
nil_version
{:FREE=>-1002, :T_STRING=>1000, :T_IMEMO=>1}
blank_version
{:FREE=>-1001, :T_STRING=>1000}
Warming up --------------------------------------
      master_version    93.351k i/100ms
         key_version    89.747k i/100ms
     present_version    91.963k i/100ms
         nil_version   103.370k i/100ms
       blank_version    74.845k i/100ms
Calculating -------------------------------------
      master_version      2.179M (±21.4%) i/s -     10.362M in   5.044668s
         key_version      2.345M (± 9.8%) i/s -     11.667M in   5.030982s
     present_version      1.738M (±14.8%) i/s -      8.553M in   5.056406s
         nil_version      2.485M (±19.1%) i/s -     11.888M in   5.015940s
       blank_version      1.951M (±12.3%) i/s -      9.580M in   5.011932s

Comparison:
         nil_version:  2484704.1 i/s
         key_version:  2344664.8 i/s - same-ish: difference falls within error
      master_version:  2178975.8 i/s - same-ish: difference falls within error
       blank_version:  1950532.0 i/s - same-ish: difference falls within error
     present_version:  1737866.7 i/s - 1.43x  slower

rel key with nil
master_version
{:FREE=>-3001, :T_STRING=>3000}
key_version
{:FREE=>-3001, :T_STRING=>3000}
present_version
{:FREE=>-1}
nil_version
{:FREE=>-1}
blank_version
{:FREE=>-1}
Warming up --------------------------------------
      master_version   112.655k i/100ms
         key_version   105.048k i/100ms
     present_version   136.219k i/100ms
         nil_version   192.026k i/100ms
       blank_version   184.846k i/100ms
Calculating -------------------------------------
      master_version      1.893M (±12.6%) i/s -      9.238M in   5.002621s
         key_version      1.672M (±13.5%) i/s -      8.194M in   5.021197s
     present_version      4.484M (±20.5%) i/s -     21.114M in   5.002982s
         nil_version      5.294M (±18.1%) i/s -     25.155M in   5.020721s
       blank_version      5.588M (± 6.7%) i/s -     27.912M in   5.019305s

Comparison:
       blank_version:  5588489.6 i/s
         nil_version:  5293929.9 i/s - same-ish: difference falls within error
     present_version:  4484493.7 i/s - same-ish: difference falls within error
      master_version:  1892919.0 i/s - 2.95x  slower
         key_version:  1672343.9 i/s - 3.34x  slower

rel key with ""
master_version
{:FREE=>-2001, :T_STRING=>2000}
key_version
{:FREE=>-2001, :T_STRING=>2000}
present_version
{:FREE=>-1}
nil_version
{:FREE=>-1001, :T_STRING=>1000}
blank_version
{:FREE=>-1}
Warming up --------------------------------------
      master_version   140.499k i/100ms
         key_version   124.738k i/100ms
     present_version   186.659k i/100ms
         nil_version   148.063k i/100ms
       blank_version   178.707k i/100ms
Calculating -------------------------------------
      master_version      1.826M (±24.2%) i/s -      8.289M in   5.026603s
         key_version      1.561M (±15.3%) i/s -      7.609M in   5.005662s
     present_version      3.622M (±19.9%) i/s -     17.173M in   5.042217s
         nil_version      2.438M (±11.5%) i/s -     12.141M in   5.053335s
       blank_version      4.911M (±15.5%) i/s -     23.768M in   5.009106s

Comparison:
       blank_version:  4910741.1 i/s
     present_version:  3622183.5 i/s - same-ish: difference falls within error
         nil_version:  2437606.2 i/s - 2.01x  slower
      master_version:  1825652.2 i/s - 2.69x  slower
         key_version:  1560530.5 i/s - 3.15x  slower
```

1 files changed, 3 insertions, 3 deletions

diff --git a/actionview/lib/action_view/helpers/url_helper.rb b/actionview/lib/action_view/helpers/url_helper.rb
index 4e436433c4..71fed39351 100644
--- a/actionview/lib/action_view/helpers/url_helper.rb
+++ b/actionview/lib/action_view/helpers/url_helper.rb
@@ -590,10 +590,10 @@ module ActionView
 
         def add_method_to_attributes!(html_options, method)
           if method && method.to_s.downcase != "get" && html_options["rel"] !~ /nofollow/
-            if html_options.key?("rel")
-              html_options["rel"] = "#{html_options["rel"]} nofollow".lstrip
-            else
+            if html_options.("rel").blank?
               html_options["rel"] = "nofollow"
+            else
+              html_options["rel"] = "#{html_options["rel"]} nofollow"
             end
           end
           html_options["data-method"] = method