Token name in RenderElementActionBase cannot be specified as nested token

Basically this part needs to be changed from

$form['token_name'] = [
      '#type' => 'machine_name',
      '#machine_name' => [
        'exists' => [$this, 'alwaysFalse'],
      ],
      '#title' => $this->t('Token name'),
      '#description' => $this->t('Optionally define a token name of this render element. It will be made available under that token name for later usage.'),
      '#default_value' => $this->configuration['token_name'],
      '#required' => FALSE,
      '#weight' => -28,
      '#eca_token_reference' => TRUE,
    ];

into

$form['token_name'] = [
      '#type' => 'textfield',
      '#maxlength' => 1024,
      '#title' => $this->t('Token name'),
      '#description' => $this->t('Optionally define a token name of this render element. It will be made available under that token name for later usage.'),
      '#default_value' => $this->configuration['token_name'],
      '#required' => FALSE,
      '#weight' => -28,
      '#eca_token_reference' => TRUE,
    ];

Hi @mxh I've added your suggestion to MR

Thank you!

This is looking good, thanks @julio_retkwa for your contribution.

We should add a follow-up issue to address the following related tasks:

• There are 11 other cases where the field type machine_name is being used, most of them allow tokens as well and could run into the same problem. We should replace them all for consistency.
• Most of those cases support tokens or require a token reference, both of which not being declared in the form field configuration. That should be added.
• Form field validation: those fields that get the token reference attribute will still be validated. But others won't. We may consider our own validation as a replacement for the machine name validation that we've then lost.

Created follow-up issue 🐛 Avoid config form field type "machine_name" Active

Merged this into 2.1.x and will now port this back and also into 3.0.x