URL with more than 10 slashes is not working in new routing system

Yeah this makes it impossible to put further level subtasks on fields, so we cannot put the translate operation on fields :/

Here's patch containing only tests that are confirming this.

Sorry. seems I removed some tags

Paths are limited to 9 parts in both new and legacy routing systems:

$ grep -nr MAX_PARTS core
core/includes/menu.inc:277:const MENU_MAX_PARTS = 9;
core/includes/menu.inc:479:    $parts = array_slice($original_map, 0, MENU_MAX_PARTS);
core/includes/menu.inc:1732:  // Note - the number of empty elements should be > MENU_MAX_PARTS.
core/includes/menu.inc:3018:  $parts = explode('/', $link_path, MENU_MAX_PARTS);
core/includes/menu.inc:3060:    $parts = explode('/', $path, MENU_MAX_PARTS);
core/lib/Drupal/Core/Routing/MatcherDumper.php:23:  const MAX_PARTS = 9;
core/lib/Drupal/Core/Routing/RouteCompiler.php:22:  const MAX_PARTS = 9;
core/lib/Drupal/Core/Routing/RouteCompiler.php:96:    $parts = explode('/', trim($path, '/'), static::MAX_PARTS);
core/lib/Drupal/Core/Routing/RouteProvider.php:245:    }), 0, MatcherDumper::MAX_PARTS);
core/modules/menu_link/lib/Drupal/menu_link/Plugin/Core/Entity/MenuLink.php:481:        $this->parts = explode('/', $this->link_path, MENU_MAX_PARTS);

It's something related to menu links but I didn't had time to investigate exactly what.

Here's a discussion related to this decision taken in D6 https://drupal.org/node/274270. Maybe @Gábor Hojtsy knows more as he was branch maintainer.

The relevant answer is exactly in that issue :) #274270-1: Future of menu depth? Increasing the limit would mean that we need more pX columns in the {menu_links} table.

Seems that "pX columns" are kept in the same table for performance reasons. It would be nice to perform a benchmark comparing the actual implementation versus storing them in a separate table (mlid, delta, value). I'm not sure that releasing the "9 limit" by storing them in other table will have a big impact on performance.

core/includes/menu.inc:277:const MENU_MAX_PARTS = 9;
core/lib/Drupal/Core/Routing/MatcherDumper.php:23:  const MAX_PARTS = 9;
core/lib/Drupal/Core/Routing/RouteCompiler.php:22:  const MAX_PARTS = 9;
core/modules/menu_link/lib/Drupal/menu_link/Plugin/Core/Entity/MenuLink.php:481:        $this->parts = explode('/', $this->link_path, MENU_MAX_PARTS);

Seems like some clean-up is in order too.

New issue for #9: #2036677: MENU_MAX_PARTS defined three times

Retroactively untagging. This is not language related.

Please let the D8MI team track issues that block our efforts. As is with the explained situation, we need to opt to use GET arguments in config translation URLs due to this limitation, instead of relying on path parts and using the standard routing system, we need to work around it in a module proposed for core. I think that is plenty reason to track this on D8MI.

Sorry... :)

Update