11.27.2020 Technical Innovation

Programmatically Adding and Populating New Fields in Drupal 8

photograph of fields from above.

Programmatically Adding and Populating New Fields in Drupal 8

​ When working on our longer-term clients’ sites, we’re often asked to add a new field (or fields) to some kind of content, and in the same batch of code to add values to those new fields. This shouldn’t be a problem – and mostly, it isn’t. The developer who’s assigned the ticket adds the fields via the Drupal GUI, the configuration for which is automatically exported via Config Suite to a folder in the git repository. Then, they write a post_update hook to add values to it. They test-run the hook (generally via drush updb), see that it works, and happily commit this new code along with the exported configuration that describes the new fields.

Sometimes, though, a problem arises when this code is deployed. Our deployment method for Drupal 8 is fairly standard:

  1. On GitHub, merge the development code into a production branch.
  2. This merge kicks off a deployment script on CircleCI that runs PHPCS and visual regression tests.
  3. Circle merges the incoming code into Pantheon’s git repo for this site, and then uses Terminus to get into the site’s “dev” environment and run: ​
    drush cr
    drush -y updb		# short for updatedb
    drush -y cim		# short for config:import
    

So, what’s the problem?

The Problem

​ The order of this operation1. drush updb updates the database and runs a post-update hook where the developer populates the new field. Afterward, with drush cim, we’re trying to import the configuration that tells Drupal to create the new field. The database update fails, and although the configuration import does run, the new values never get put into it. ​ ​

The Solution

​ The following code lays out one way to address this problem. Assuming we’re doing this work for a custom module called “Test,” we’d add this to its install file: ​ modules/custom/test/test.install

<?php

use Drupal\Core\Config\FileStorage;
use Drupal\field\Entity\FieldConfig;
use Drupal\field\Entity\FieldStorageConfig;
use Drupal\node\Entity\Node;

/**
 * Be sure the fields we're expecting are there, and create if not.
 *
 * ASSUMPTIONS:
 * - You've already created these field configs, probably through the GUI.
 * - They're stored in ../config.
 *
 * @param array $entitytypes_fields
 *   A 3-dimensional array. The first level is entity types, the second is
 * bundles, and the third is the fields you want to ensure. E.g.
 * [
 *   'node' => [
 *     'page' => [
 *       'field_foo',
 *       'field_bar',
 *     ],
 *     'article' => [
 *       'field_bar',
 *     ],
 *   ],
 * ]
 *
 * @throws \Drupal\Core\Entity\EntityStorageException
 */
function _ensure_fields(array $entitytypes_fields) {
  $config_directory = new FileStorage('../config');

  foreach ($entitytypes_fields as $entitytype => $bundles) {
    foreach ($bundles as $bundle => $fields) {
      foreach ($fields as $field) {
        $field_storage_name = 'field.storage.' . $entitytype . '.' . $field;
        $config_record = $config_directory->read($field_storage_name);
        if (!FieldStorageConfig::loadByName($config_record['entity_type'], $config_record['field_name'])) {
          FieldStorageConfig::create($config_record)->save();
        }

        $field_config_name = 'field.field.' . $entitytype . '.' . $bundle . '.' . $field;
        $config_record = $config_directory->read($field_config_name);
        if (!FieldConfig::loadByName($config_record['entity_type'], $config_record['bundle'], $config_record['field_name'])) {
          FieldConfig::create($config_record)->save();
        }
      }
    }
  }
}

_ensure_fields() is a custom function I wrote to address this situation. Here are some things to remember: ​

  1. Be sure that you already have the necessary configuration files saved somewhere–these should look like “field.storage.[ENTITY TYPE].[FIELD NAME].yml” and “field.field.[ENTITY TYPE].[BUNDLE].[FIELD NAME].yml”–and if that somewhere isn’t ../config as expected by this function, just change where the function’s looking.
  2. Include this function in the .install file of your module.
  3. Use it in your hook_update_N() function per its documentation. ​

Here’s _ensure_fields() in action, a little further down the test.install file. We’re adding field_external_id to two node types, and, just for good measure, adding a field_second_image field to a paragraph type at the same time. ​

/**
 * Adds "External ID" field to articles and "Second image" to two-col CTAs.
 */
function test_update_8101(&$sandbox) {
  $entitytypes_fields = [
    'node' => [
      'page' => [
        'field_external_id',
      ],
      'blog_news_post' => [
        'field_external_id',
      ],
    ],
    'paragraph' => [
      'two_column_cta' => [
        'field_second_image',
      ],
    ],
  ];

  _ensure_fields($entitytypes_fields);
}

​ Finally, we’d add new values to the fields in that post-update hook like so: ​ ​ modules/custom/test/test.post_update.php

<?php

/**
 * Populate the new "External ID" field from an array of known values.
 */
function test_post_update_populate_id_field(&$sandbox) {
  $nids_to_extids = [
    76432 => 'HhZLS',
    76428 => 'RKWrd',
    76425 => 'TJs22',
    76424 => 'wpVIR',
    76423 => 'AEyS9',
    76418 => 'tSVVJ',
    76415 => 'tF4NJ',
    76414 => 'MXmnc',
    76413 => 'aQLwW',
    76412 => 'NVRV0',
    76411 => 'gk55Q',
    76410 => 'Wj1DC',
    76406 => 'CuCjT',
    76405 => '4qYFe',
    76393 => 'cBPyY',
    76390 => 'MmWJl',
    76388 => 'K4QYQ',
    76387 => 'HUpeh',
    76386 => 'P3MN2',
    76385 => 'qALjM',
  ];

  $nodes = \Drupal::entityTypeManager()->getStorage('node')->loadMultiple(array_keys($nids_to_extids));
  foreach ($nodes as $node) {
    $node->set('field_external_id', $nids_to_extids[$node->id()]);
    $node->save();
  }
}

​ The deployment ought to go smoothly now–the new fields are added as expected, and then their values get populated. ​

Last note: Why the post_update hook?

​ It is technically possible to add the fields and also populate them within our hook_update_N function, skipping the post_update hook altogether. Although the documentation for exactly what sort of work should be done in one versus the other can be confusing, the hook_update_N docs are clear that in these functions, loading, saving, or performing any other CRUD operation on an entity is never safe to do (they always involve hooks and services).

Instead: make your field changes in hook_update_N, then make your content changes in post_update hooks.

Referenced

1. Which is standard for this kind of deployment. See, for instance, the drush deploy command, which effectively does the same thing, and this useful StackExchange discussion on the matter.

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