How can I use 'format_type' => 'custom' for a datetime field?

Question

I have a custom entity with (among others) a field defined this way:

$fields['duedate'] = BaseFieldDefinition::create('datetime')
  ->setLabel(t('Due Date'))
  ->setSetting('datetime_type', 'date')
  ->setDefaultValue(array(0 => array(
    'default_date_type' => 'now',
    'default_date' => '2050-12-31',
  )))
  ->setDisplayOptions('view', [
  'type' => 'datetime_default',
  'settings' => [
    'format_type' => 'date_courte',
  ],
    'weight' => 5,
  ])
  ->setDisplayOptions('form', array(
    'weight' => 5,
  ))
  ->setDisplayConfigurable('form', TRUE)
  ->setDisplayConfigurable('view', TRUE);

'date_courte' is a custom date format I created to display date as 'dd/mm/yyyy'. And it works!
I'd like to have the same result without using 'date_courte' so I tried

  'settings' => [
    'format_type' => 'custom',
    'format' => 'd/m/Y',
  ],

instead of

  'settings' => [
    'format_type' => 'date_courte',
  ],

And it doesn't work!

I'm pretty sure of 'format_type' => 'custom'.
I think the problem comes from 'format' in 'format' => 'd/m/Y'.

What should be the correct syntax?

Answer 1

I'm pretty sure you need to use the datetime_custom display type vs datetime_default. You won't need to pass the format_type parameter in your settings array. You will end up with something like:

...
->setDisplayOptions('view', [
  'type' => 'datetime_custom',
  'settings' => [
    'date_format' => 'd/m/Y',
  ],
...

That should work how you'd like. The datetime_custom formatter is defined in core's datetime module.