Global Redirect enforce trailing slash setting not respected

Thanks for reporting this one.

I installed Smart Paging with Trailing Slash and Global Redirect and, other than a quirk with the pager dropdown, it seemed to work OK. Can you please provide me with more info on what doesn't work when it has a trailing slash?

You are right that turning the "Enforce trailing slash" option off in Global Redirect doesn't work - I hadn't actually tested this. Probably not an easy fix for this without changes to Global Redirect code. :(

I would recommend looking deeper into the issue Smart Paging has with Trailing Slashes, as supporting both trailing slashes and not isn't great for SEO:
http://googlewebmastercentral.blogspot.com.au/2010/04/to-slash-or-not-to...

Another thing you could do is switch to web server redirects for SEO (eg. mod_rewrite), rather than Global Redirect.

That said, I do need to fix the Global Redirect issue you raised so let's focus on that.

Global Redirect does these redirects on Drupal boot (before even processing the page). It doesn't provide any hooks for this process which is why the behavior is hard to alter without making code changes to Global Redirect itself.

I reckon I might know a way to fix the problem however - it won't be pretty coding wise, but should work.
Will hopefully post some code for you to test soon.

More Info about How Trailing Slash and Global Redirect Work

Trailing Slash and Global Redirect do two distinctly different things: Trailing Slash ensures that Drupal outputs links to URLs with trailing slashes (eg. <a href="/node/1/">Node 1</a>). Global Redirect determines when a user has arrived at an incorrect URL (in this case one without a slash) and redirects them to the right URL.

Trailing Slash off, Global Redirect enforce trailing slash off:
Default Drupal URL behaviour - no trailing slashes.

Trailing Slash on, Global Redirect enforce trailing slash off:
Every Drupal link a user clicks on will take them to a trailing slash URL. If a user does go to a non trailing slash URL they will not be redirected. This creates duplicate content for users and search engines.

Trailing Slash off, Global Redirect enforce trailing slash on:
Every link a user clicks on will take them to a non trailing slash URL. They will then be redirected to the equivalent trailing slash URL. This effectively doubles the number of requests made to the web server and Drupal which is not good for web server performance. Edit: Not possible as turning Trailing Slash off makes Global Redirect enforce no trailing slash again.

Trailing Slash on, Global Redirect enforce trailing slash on:
Every Drupal link a user clicks on will take them to a trailing slash URL. If a user does go to a non trailing slash URL they will be redirected. This is the ideal.

OK, please try the following code/patch and let me know if it allows Global Redirect to not enforce trailing slashes.

Replace the whole trailing_slash_url_outbound_alter() function in trailing_slash.module file with:

/**
 * Implements hook_url_outbound_alter().
 */
function trailing_slash_url_outbound_alter(&$path, &$options, $original_path) {
  // If Clean URLs and Trailing Slashes aren't enabled, don't run.
  if (empty($GLOBALS['conf']['clean_url']) || !variable_get('trailing_slash', TRUE)) {
    return;
  }

  // If URL is empty but has a prefix, set the path to the prefix.
  if (($path == '<front>' || empty($path)) && isset($options['prefix']) && $options['prefix'] != '') {
    $path = $options['prefix'];
    $options['prefix'] = '';
  }

  // If the URL is external, the front page, or an empty path, don't run.
  if ($options['external'] || $path == '<front>' || empty($path)) {
    return;
  }

  // If Global Redirect is installed but not being used to enforce trailing
  // slashes, we need to not add a trailing slash when it checks to see if a
  // page needs to be redirected.
  if (module_exists('globalredirect') && ($settings = _globalredirect_get_settings()) && _globalredirect_is_active($settings) && !$settings['deslash']) {
    // Use backtrace to find out if the globalredirect_init() function called
    // this function.
    $backtrace = debug_backtrace();
    if (isset($backtrace[2]) && isset($backtrace[2]['function']) && strtolower($backtrace[2]['function']) == 'globalredirect_init') {
      return;
    }
  }

  // Pre-alias if not already an alias. The only available hook is before
  // aliasing is done, so we need to pre-alias to modify the final URL path.
  if (!$options['alias']) {
    // This is a copy of Drupal core code.
    $language = isset($options['language']) && isset($options['language']->language) ? $options['language']->language : '';
    $alias = drupal_get_path_alias($original_path, $language);
    if ($alias != $original_path) {
      $path = $alias;
    }
    // This is where the copy of Drupal core code ends.

    // Mark the path as an alias so the alias code isn't needlessly re-run.
    $options['alias'] = TRUE;
  }

  // Add a trailing slash.
  trailing_slash_add($path);
}

Thanks for testing!!

Yeah, that's the "won't be pretty" part. :/
It's not ideal, but I'm willing to call this a fringe case.

Below is a tweak to help improve memory usage and release:

    $backtrace = debug_backtrace(DEBUG_BACKTRACE_IGNORE_ARGS, 3);
    if (isset($backtrace[2]) && isset($backtrace[2]['function']) && strtolower($backtrace[2]['function']) == 'globalredirect_init') {
      return;
    }
    unset($backtrace);

Committed and will include this in RC5.

Title need make better english... o.O