Get rid of strtr in UrlGenerator, it is not needed

Micro-optimization, but it is well known that str_replace is faster than strtr, so lets do that.

Should we also file an upstream issue?

1. +++ b/core/lib/Drupal/Core/Routing/UrlGenerator.php
   @@ -54,14 +54,16 @@ class UrlGenerator implements UrlGeneratorInterface {
   +   * The format are the two first parameter of str_replace().
   

   This is difficult to parse.

2. +++ b/core/lib/Drupal/Core/Routing/UrlGenerator.php
   @@ -54,14 +54,16 @@ class UrlGenerator implements UrlGeneratorInterface {
   +    ['%2F'], ['/']
   

   Can we put these on separate lines, to remove the visual suggestion that this is a key-value map?

Maybe better to use a list() construct here? I think it's clearer to read.

RTBC+1

+++ b/core/lib/Drupal/Core/Routing/UrlGenerator.php
@@ -212,7 +215,8 @@ protected function doGenerate(array $variables, array $defaults, array $tokens,
-    $url = strtr(rawurlencode($url), $this->decodedChars);
+    list($search_strings, $replacement_strings) = $this->decodedChars;
+    $url = str_replace($search_strings, $replacement_strings, rawurlencode($url));

So what's actually faster... if we're doing a micro-optimisation adding an extra operation seem interesting.

#10:

"Like array(), this is not really a function, but a language construct. list() is used to assign a list of variables in one operation."

(http://php.net/manual/en/function.list.php)

So this should be identical to using:

$search_strings = $this->decodedChars[0];
$replacement_strings = $this->decodedChars[1];

However I benchmarked the cases and this is the result:

str_tr: 5.160556s 0.000000s
str_replace: 1.017935s 0.000000s
str_replace_variables: 1.051348s 0.000000s
str_replace_list: 1.055539s 0.000000s
str_replace_single: 0.663118s 0.000000s
str_replace_list_single: 0.920595s 0.000000s
str_replace_single_isset: 0.940557s 0.000000s

with the following scenarios (xhprof off):

$test_bases['str_tr'] = function() {
  $url = 'foo/bar/bla';
  $decodedChars = [
    '%2F' => '/',
  ];
  $url = strtr(rawurlencode($url), $decodedChars);
};

$test_bases['str_replace'] = function() {
  $url = 'foo/bar/bla';
  $decodedChars = [
    ['%2F'], // Map from these encoded characters.
    ['/'], // Map to these decoded characters.
  ];
  $url = str_replace($decodedChars[0], $decodedChars[1], rawurlencode($url));
};

$test_bases['str_replace_variables'] = function() {
  $url = 'foo/bar/bla';
  $decodedChars = [
    ['%2F'], // Map from these encoded characters.
    ['/'], // Map to these decoded characters.
  ];

  $search_strings = $decodedChars[0];
  $replacement_strings = $decodedChars[0];
  $url = str_replace($search_strings, $replacement_strings, rawurlencode($url));
};

$test_bases['str_replace_list'] = function() {
  $url = 'foo/bar/bla';
  $decodedChars = [
    ['%2F'], // Map from these encoded characters.
    ['/'], // Map to these decoded characters.
  ];
  list($search_strings, $replacement_strings) = $decodedChars;
  $url = str_replace($search_strings, $replacement_strings, rawurlencode($url));
};

$test_bases['str_replace_single'] = function() {
  $url = 'foo/bar/bla';
  $decodedChars = [
    '%2F', // Map from these encoded characters.
    '/', // Map to these decoded characters.
  ];
  $url = str_replace($decodedChars[0], $decodedChars[1], rawurlencode($url));
};

$test_bases['str_replace_list_single'] = function() {
  $url = 'foo/bar/bla';
  $decodedChars = [
    ['%2F'], // Map from these encoded characters.
    ['/'], // Map to these decoded characters.
  ];
  list($search_strings, $replacement_strings) = $decodedChars;
  $url = str_replace($search_strings[0], $replacement_strings[0], rawurlencode($url));
};

$test_bases['str_replace_single_isset'] = function() {
  $url = 'foo/bar/bla';
  $decodedChars = [
    ['%2F'], // Map from these encoded characters.
    ['/'], // Map to these decoded characters.
  ];
  $search_strings = $decodedChars[0];
  $replacement_strings = $decodedChars[0];
  if (!isset($search_strings[1])) {
    $url = str_replace($search_strings[0], $replacement_strings[0], rawurlencode($url));
  }
  else {
    $url = str_replace($search_strings, $replacement_strings, rawurlencode($url));
  }
};

So yes, list() is slightly slower than directly using decodedChars[0] and decodedChars[1], but is the same when using temporary variables.

Obviously the single case is fasted, but any optimization is likely not worth the additional complexity of the isset(), etc. and part of that is also saving one array traversal.

So it is probably just the 5x improvement over str_tr that really matters here - unless we never have a use-case to support more than one encoded character.

Oh, that is a very sweet solution :).

Thanks everyone! Committed 3555e2b and pushed to 8.0.x. Thanks!

Thank you for adding the beta evaluation to the issue summary.