Enable Custom Prompt Link

The proposed change is fairly simple:

diff --git a/onesignal.module b/onesignal.module
index b1063c7e3ef42044800dce580efebbad20c60470..d17f4eef031dfc308871fd58d886a4e0784de389 100644
--- a/onesignal.module
+++ b/onesignal.module
@@ -140,8 +140,9 @@ function onesignal_page_attachments(&$attachments) {
     '#template' => "
         var OneSignal = window.OneSignal || [];
         OneSignal.push(function() {
+          var ___OneSignalDrupalModuleConfig = {{ onesignal_json|raw }};
           {{ extra_js|raw }}
-          OneSignal.init({{ onesignal_json|raw }});
+          OneSignal.init(___OneSignalDrupalModuleConfig);
         });
       ",
     '#context' => [

This allows `extra_js` to modify `___OneSignalDrupalModuleConfig`, e.g.

// Source: https://documentation.onesignal.com/docs/custom-link-prompt#step-3-provide-configuration
___OneSignalDrupalModuleConfig ['promptOptions'] = {
  customlink: {
    enabled: true, /* Required to use the Custom Link */
    style: "button", /* Has value of 'button' or 'link' */
    size: "medium", /* One of 'small', 'medium', or 'large' */
    color: {
      button: '#E12D30', /* Color of the button background if style = "button" */
      text: '#FFFFFF', /* Color of the prompt's text */
    },
    text: {
      subscribe: "Subscribe to push notifications", /* Prompt's text when not subscribed */
      unsubscribe: "Unsubscribe from push notifications", /* Prompt's text when subscribed */
      explanation: "Get updates from all sorts of things that matter to you", /* Optional text appearing before the prompt button */
    },
    unsubscribeEnabled: true, /* Controls whether the prompt is visible after subscription */
  }
}

Final code to enable a custom prompt + bell notification.

Requires updating the script to v16.

(Remember to enable permissions for the OneSignal scripts to load!)

function MY_MODULE_onesignal_extra_js() {

  $current_path = \Drupal::service('path.current')->getPath();
  if ($current_path != '/node/777') {
    return;
  }

  $addCustomPrompt = "
    // Source: https://documentation.onesignal.com/docs/custom-link-prompt#step-3-provide-configuration
    var promptOptions = {
      promptOptions: {
        customlink: {
          enabled: true, /* Required to use the Custom Link */
          style: 'button', /* Has value of 'button' or 'link' */
          size: 'medium', /* One of 'small', 'medium', or 'large' */
          color: {
            button: '#E12D30', /* Color of the button background if style = 'button' */
            text: '#FFFFFF', /* Color of the prompt's text */
          },
          text: {
            subscribe: 'Subscribe to push notifications', /* Prompt's text when not subscribed */
            unsubscribe: 'Unsubscribe from push notifications', /* Prompt's text when subscribed */
            explanation: 'Get updates from all sorts of things that matter to you', /* Optional text appearing before the prompt button */
          },
          unsubscribeEnabled: true, /* Controls whether the prompt is visible after subscription */
        }
      }
    }

    var notifyButton = {
      notifyButton: {
          enable: true
      },
    };

    var serviceWorkerOptions = { 
      serviceWorkerParam: { scope: '/OneSignal/' },
      serviceWorkerPath: 'OneSignal/OneSignalSDKWorker.js',
    };

    Object.assign(___OneSignalDrupalModuleConfig, promptOptions, notifyButton, serviceWorkerOptions);
  ";

  return $addCustomPrompt;
}

I need this approach too, maybe it could be rearranged to something like:

onesignal.module line 135:

// Grab any extra js to be included.
$extra_js = \Drupal::service('module_handler')->invokeAll('onesignal_extra_js');
+ \Drupal::service('module_handler')->alter('onesignal_config', $config);

to cover simply the declarations that not imply new functions. So then simply with a

function mymodule_onesignal_config_alter(&$config) {
  $config['notifyButton']['size'] = 'small';
}

One can theme easily.