"IN" operator for addWhere() not returning data

[antipode3141592]

I'm having trouble getting results when using the "IN" operator in where clauses to search for multiple options (ex: search for all contacts that have selected both Volunteering and Newsletter among their contact preferences).

Using the API4 Explorer, this is php output

$contacts = \Civi\Api4\Contact::get()
  ->setSelect([
    'id', 
    'contact_type', 
    'display_name', 
    'Interests.Contact_Interests',
  ])
  ->addWhere('Interests.Contact_Interests', 'IN', ['Volunteering', 'Newsletter'])
  ->setLimit(25)
  ->execute(); 

Which yields no results. Notably, when I switch 'IN' to 'NOT IN', it returns all contacts with non-empty Contact_Interests, so it seems like this is an API issue.

Using the API3 Explorer:

$result = civicrm_api3('Contact', 'get', [
  'sequential' => 1,
  'return' => ["id", "contact_type", "display_name", "custom_25"],
  'custom_25' => ['IN' => ["Newsletter", "Volunteering"]],
]);

This call does return the correct results.

[colemanw]

Which version of api4 are you using? This extension or the one in core?
Is this a multiselect custom field or does it hold a single value?
And are "Newsletter" and "Volunteering" the option names or ids or labels or what?

[antipode3141592]

CiviCRM 5.18.3 with API extension 4.5.2. I am trying to search on a multiselect custom field (Set name is Interests, and the options Newsletter and Volunteering are both the label and the value).

[colemanw]

Multiselects are tricky because of the way the data is serialized. I don't think api4 has been taught that trick yet.