In the routing system you can't do this. What you can do is path aliasing.

Inbound: /{bar}/foo/{baz} -> /foo/{bar}/{baz}

Outbound: /foo/{bar}/{baz} -> /{bar}/foo/{baz}

You need a pattern to apply a regular expression on the path inbound, so /{bar}/{baz} is only possible if the parameters themselves have a distinctive pattern.

I didn't find a tutorial how to build a pathprocessor, but you can use this example from core for the scaffolding: http://cgit.drupalcode.org/drupal/tree/core/lib/Drupal/Core/PathProcessor/PathProcessorFront.php

and register both as tagged service in *.services.yml

services:
  path_processor_front:
    class: Drupal\Core\PathProcessor\PathProcessorFront
    tags:
      - { name: path_processor_inbound, priority: 200 }
      - { name: path_processor_outbound, priority: 200 }
    arguments: ['@config.factory']

In the routing system you can't do this. What you can do is path aliasing.

Inbound: /{bar}/foo/{baz} -> /foo/{bar}/{baz}

Outbound: /foo/{bar}/{baz} -> /{bar}/foo/{baz}

You need a pattern to apply a regular expression on the path inbound, so /{bar}/{baz} is only possible if the parameters themselves have a distinctive pattern.

I didn't find a tutorial how to build a path processor, but you can use the PathProcessorFront class as example.

Register both as tagged service in the .services.yml file for the module.

services:
  path_processor_front:
    class: Drupal\Core\PathProcessor\PathProcessorFront
    tags:
      - { name: path_processor_inbound, priority: 200 }
      - { name: path_processor_outbound, priority: 200 }
    arguments: ['@config.factory']

In the routing system you can't do this. What you can do is path aliasing.

Inbound: /{bar}/foo/{baz} -> /foo/{bar}/{baz}

Outbound: /foo/{bar}/{baz} -> /{bar}/foo/{baz}

You need a pattern to apply a regular expression on the path inbound, so /{bar}/{baz} is only possible if the parameters themselves have a distinctive pattern.

I didn't find a tutorial how to build a pathprocessor, but you can use this example from core for the scaffolding: http://cgit.drupalcode.org/drupal/tree/core/lib/Drupal/Core/PathProcessor/PathProcessorFront.php

and register both as tagged service in *.services.yml

path_processor_front:
    class: Drupal\Core\PathProcessor\PathProcessorFront
    tags:
      - { name: path_processor_inbound, priority: 200 }
      - { name: path_processor_outbound, priority: 200 }
    arguments: ['@config.factory']

In the routing system you can't do this. What you can do is path aliasing.

Inbound: /{bar}/foo/{baz} -> /foo/{bar}/{baz}

Outbound: /foo/{bar}/{baz} -> /{bar}/foo/{baz}

You need a pattern to apply a regular expression on the path inbound, so /{bar}/{baz} is only possible if the parameters themselves have a distinctive pattern.

I didn't find a tutorial how to build a pathprocessor, but you can use this example from core for the scaffolding: http://cgit.drupalcode.org/drupal/tree/core/lib/Drupal/Core/PathProcessor/PathProcessorFront.php

and register both as tagged service in *.services.yml

services:
  path_processor_front:
    class: Drupal\Core\PathProcessor\PathProcessorFront
    tags:
      - { name: path_processor_inbound, priority: 200 }
      - { name: path_processor_outbound, priority: 200 }
    arguments: ['@config.factory']