Query.php

<?php

namespace Drupal\workspaces\EntityQuery;

use Drupal\Core\Entity\Query\Sql\Query as BaseQuery;

/**
 * Alters entity queries to use a workspace revision instead of the default one.
 */
class Query extends BaseQuery {
    use QueryTrait {
        prepare as traitPrepare;
    }
    
    /**
     * {@inheritdoc}
     */
    public function prepare() {
        $this->traitPrepare();
        // If the prepare() method from the trait decided that we need to alter this
        // query, we need to re-define the key fields for fetchAllKeyed() as SQL
        // expressions.
        if ($this->sqlQuery
            ->getMetaData('active_workspace_id')) {
            $id_field = $this->entityType
                ->getKey('id');
            $revision_field = $this->entityType
                ->getKey('revision');
            // Since the query is against the base table, we have to take into account
            // that the revision ID might come from the workspace_association
            // relationship, and, as a consequence, the revision ID field is no longer
            // a simple SQL field but an expression.
            $this->sqlFields = [];
            $this->sqlQuery
                ->addExpression("COALESCE(workspace_association.target_entity_revision_id, base_table.{$revision_field})", $revision_field);
            $this->sqlQuery
                ->addExpression("base_table.{$id_field}", $id_field);
            $this->sqlGroupBy['workspace_association.target_entity_revision_id'] = 'workspace_association.target_entity_revision_id';
            $this->sqlGroupBy["base_table.{$id_field}"] = "base_table.{$id_field}";
            $this->sqlGroupBy["base_table.{$revision_field}"] = "base_table.{$revision_field}";
        }
        return $this;
    }

}