Retrieve Custom Field Values for Phabricator Objects

Phabricator is an incredibly well-coded PHP application but lacks a bit on the documentation side.  Then again, what open source project isn't?  Over the past months I've been slowly integrating Phabricator, a newish review tool, with Bugzilla, a much older tool.  The most recent step saw me needing to add a custom field (DifferentialCommitMessageCustomField class extension) to revisions:

Creating the DifferentialCommitMessageCustomField extension was fairly simple but, due to the structure of DifferentialRevision and other Phabricator classes, retrieving that field value isn't as easy as one would hope.  After trying a variety of methods and combing through the classes chain source code, it was Aviv Eyal that provided a nice utility function for retrieving custom field data for a given Phabricator object type:

function get_custom_field_value($object, $key_field) {
  $field = PhabricatorCustomField::getObjectField(
    $object,
    PhabricatorCustomField::ROLE_DEFAULT,
    $key_field
  );

  id(new PhabricatorCustomFieldStorageQuery())
  ->addField($field)
  ->execute();

  $value = $field->getValueForStorage();

  return $value;
}

In my case, the $object was a DifferentialRevision and the $key_field is differential:bugzilla-bug-id, defined within my DifferentialCommitMessageCustomField extension.  If you are adding a CustomField of any kind to any Phabrication application, you can use this same method.

When documentation is lacking and inheritance levels a dozen levels deep, it's great that community members can jump in to help each other -- it speaks volumes for the project.