Add mailchimp_sf_list_limit filter to allow modifying the list limit.

[iamdharmesh]

Description of the Change

This pull request refactors how Mailchimp lists are fetched throughout the codebase by introducing a new helper function, mailchimp_sf_get_lists(). This change centralizes the logic for retrieving lists, making it easier to maintain and allowing for customization of the fetch limit via a filter. The update replaces direct API calls in several locations with the new helper function.

Centralization and Reusability:

• Added a new function, mailchimp_sf_get_lists(), in mailchimp.php to encapsulate the logic for fetching Mailchimp lists, including support for customizing the fetch limit through the mailchimp_sf_list_limit filter.

Codebase Refactoring:

• Replaced direct API calls to $api->get('lists', ...) with calls to the new mailchimp_sf_get_lists() function in the following places:
  • includes/admin/templates/settings.php
  • includes/blocks/class-mailchimp-list-subscribe-form-blocks.php (get_lists method)
  • includes/class-mailchimp-admin.php (verify_and_save_oauth_token method)
  • mailchimp.php (mailchimp_sf_change_list_if_necessary function)

Closes #186

How to test the Change

1. Connect a Mailchimp account with more than one list.
2. Add the following code snippet to the theme’s functions.php file:

// For testing purposes, set the limit to 1.
add_filter( 'mailchimp_sf_list_limit', function( $limit ) {
    return 1;
} );

3. Check the list dropdown on the settings page and ensure that only one list is displayed.
4. Perform overall smoke testing.

Changelog Entry

Added - The mailchimp_sf_list_limit filter to allow modifying the list limit.

Credits

Props @jonjennings @iamdharmesh

Checklist:

• I agree to follow this project's Code of Conduct.
• I have updated the documentation accordingly.
• I have added tests to cover my change.
• All new and existing tests pass.

[Copilot]

Pull request overview

This PR centralizes Mailchimp list retrieval behind a new mailchimp_sf_get_lists() helper and introduces a mailchimp_sf_list_limit filter so integrators can adjust how many lists are fetched, replacing several direct $api->get( 'lists', ... ) calls across admin UI, blocks, and token verification.

Changes:

• Added mailchimp_sf_get_lists() in mailchimp.php, including the mailchimp_sf_list_limit filter.
• Replaced direct Mailchimp API list-fetch calls with mailchimp_sf_get_lists() in admin settings, block list loading, OAuth token verification, and list-change handling.
• Removed old inline comments around the hard-coded 100-list limit in multiple locations.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 7 comments.

File	Description
mailchimp.php	Adds mailchimp_sf_get_lists() + filter, and refactors list-change logic to use the helper.
includes/class-mailchimp-admin.php	Uses the helper when validating/refreshing saved list data during OAuth token verification.
includes/blocks/class-mailchimp-list-subscribe-form-blocks.php	Uses the helper when populating block list data (and caching it to options).
includes/admin/templates/settings.php	Uses the helper to populate the settings-page list dropdown.

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