Solution for ENUM datatype for MySQL

I have managed to get working a solution for the ENUM datatype for MySQL. I don't yet know how to create patches etc. so I put describe here my work and I hope that if you are looking for a way to make this work you can use my work to help you, or even better, if you are able to make this fix get into core, all the better.

In your database schema add an extra item called 'enum_items' as shown in the example below:

...

 $schema['vchess_games'] = array(
      'description' => 'This table contains a summary of each game',
      'fields' => array(
          'turn' => array(
              'description' => 'Whose turn it is to play, either "w" (white) or "b" (black)',
              'type' => 'enum',
              'enum_items' => array('w', 'b'),
              'not null' => TRUE,
              'default' => 'w',
          ),
       'status' => array(
              'description' => 'Status of the game',
              'type' => 'enum',
              'enum_items' => array('in progress','1/2-1/2','1-0','0-1'),
              'not null' => TRUE,
          ),
...

In the MySQL version of schema.inc in /includes/database/mysql/schema.inc file add code for using these ENUM items:

protected function createFieldSql($name, $spec) {
    $sql = "`" . $name . "` " . $spec['mysql_type'];

    if (in_array($spec['mysql_type'], array('VARCHAR', 'CHAR', 'TINYTEXT', 'MEDIUMTEXT', 'LONGTEXT', 'TEXT')) && isset($spec['length'])) {
      $sql .= '(' . $spec['length'] . ')';
    }
    // New ENUM code begins here:
    elseif ($spec['mysql_type'] == 'ENUM') {
      // Build a string of the enum items like "('a','b','c')"
      $sql .= '(';
      foreach ($spec['enum_items'] as $enum_item) {
        $sql .= "'" . $enum_item . "',";
      }
      $sql = trim($sql, ",");  // Remove the final trailing comma
      $sql .= ')';
    }
    // End of new ENUM code
    elseif (isset($spec['precision']) && isset($spec['scale'])) {
      $sql .= '(' . $spec['precision'] . ', ' . $spec['scale'] . ')';
    }
...

In the same file, add 'enum:normal' => 'ENUM', to the getFieldTypeMap() function:

    public function getFieldTypeMap() {
    // Put :normal last so it gets preserved by array_flip. This makes
    // it much easier for modules (such as schema.module) to map
    // database types back into schema types.
    // $map does not use drupal_static as its value never changes.
    static $map = array(
      'varchar:normal'  => 'VARCHAR',
      'char:normal'     => 'CHAR',

      'text:tiny'       => 'TINYTEXT',
      'text:small'      => 'TINYTEXT',
      'text:medium'     => 'MEDIUMTEXT',
      'text:big'        => 'LONGTEXT',
      'text:normal'     => 'TEXT',

      'serial:tiny'     => 'TINYINT',
      'serial:small'    => 'SMALLINT',
      'serial:medium'   => 'MEDIUMINT',
      'serial:big'      => 'BIGINT',
      'serial:normal'   => 'INT',

      'int:tiny'        => 'TINYINT',
      'int:small'       => 'SMALLINT',
      'int:medium'      => 'MEDIUMINT',
      'int:big'         => 'BIGINT',
      'int:normal'      => 'INT',

      'float:tiny'      => 'FLOAT',
      'float:small'     => 'FLOAT',
      'float:medium'    => 'FLOAT',
      'float:big'       => 'DOUBLE',
      'float:normal'    => 'FLOAT',

      'numeric:normal'  => 'DECIMAL',
        
      'enum:normal'    => 'ENUM',   // This is the line to add for ENUM

      'blob:big'        => 'LONGBLOB',
      'blob:normal'     => 'BLOB',
    );
    return $map;
  }

I'm absolutely delighted it's working for me; it's the first time I've ever tried to patch anything in core! I hope that this work can also help others to get it working.