feat: add dynamic lists based on submitted values

[mnlmaier]

Hey, needed this for a feature in a project I am currently working on. Users should be able to pick which newsletters they'd like to subscribe to.

Thought it might be useful, if not, feel free to just close the PR and I'll continue working with my fork.

Thanks for the plugin!
Manuel

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Lists were static per form, so every contact ended up in the same lists. Forms that let people pick what they want to receive had no way to route contacts to matching lists.

Enabling Dynamic Lists reveals a set of rules that map a form field and an expected value to additional lists, and makes Lists optional so the submission alone can determine where a contact ends up. Array values, such as a checkboxes field, match when the value is one of the selected options, so picking multiple options adds the contact to multiple lists. Leaving the value blank matches any truthy value. Matching rules are combined with the configured lists and deduplicated, for both regular and double opt-in contacts.

[thomasvantuycom]

Hi @mnlmaier,

Thank you for the PR. I can definitely see how this functionality would be useful, but I'm wondering whether the proposed solution is the best and most general approach.

Having dynamic lists based on submitted form values is certainly useful and, in some cases, necessary. However, I'm not particularly fond of the current dynamic rules UI, where users have to manually copy the possible values of a form field and map each one to one or more lists. This feels somewhat cumbersome and error-prone, especially when the form field already represents the values we want to use. I'd rather have the value field be a select in that case, although that's more complex and something I'd need to investigate to see if it's possible.

I can also imagine a use case where someone simply wants a form field to determine the lists a submission should be added to. In that case, the addon would either need an additional lists_field option, or users would have to create a redundant mapping where each field value is manually mapped to a list with the same value.

Another solution for these cases would be to use a listener:

<?php

namespace App\Listeners;

use Statamic\Events\FormSubmitted;

class SetSubmissionBrevoLists
{
    public function handle(FormSubmitted $event): void
    {
        $submission = $event->submission;
        $form = $submission->form();

        if ($form->has('brevo')) {
            $config = collect($form->get('brevo'));
            $lists = $config->get('lists', []);

            $topicLists = [
                'banking'  => [2],
                'payments' => [3, 4],
                'commerce' => [5],
            ];

            $roleLists = [
                'partner' => [6],
                'member'  => [7],
            ];

            $additionalLists = [
                ...($topicLists[$submission->get('topics')] ?? []),
                ...($roleLists[$submission->get('role')] ?? []),
            ];

            $config->set(
                'lists',
                array_values(array_unique(array_merge($lists, $additionalLists)))
            );

            $form->set('brevo', $config);
            $submission->form($form);

            $event->submission = $submission;
        }
    }
}

Of course, I understand that having this functionality available through the UI would be preferable, so I'm not necessarily suggesting that listeners are the ideal solution. I'm mainly wondering if there's a more generic approach we could take that covers these use cases without requiring users to duplicate information that's already present in their form configuration.