Doctrine custom DQL string function for PostgreSQL string_agg with supports DISTINCT and ORDER BY clause

gistfile1.txt

<?php

namespace App\DQL;

use Doctrine\ORM\Query\AST\Functions\FunctionNode;
use Doctrine\ORM\Query\AST\Literal;
use Doctrine\ORM\Query\AST\OrderByClause;
use Doctrine\ORM\Query\AST\PathExpression;
use Doctrine\ORM\Query\Lexer;
use Doctrine\ORM\Query\Parser;
use Doctrine\ORM\Query\SqlWalker;

/**
 * StringAgg.
 */
class StringAgg extends FunctionNode
{
    /**
     * @var PathExpression|null
     */
    private $expression = null;

    /**
     * @var Literal|null
     */
    private $delimiter = null;

    /**
     * @var bool
     */
    private $isDistinct = false;

    /**
     * @var OrderByClause|null
     */
    public $orderBy = null;

    /**
     * @param Parser $parser
     */
    public function parse(Parser $parser): void
    {
        $parser->match(Lexer::T_IDENTIFIER);
        $parser->match(Lexer::T_OPEN_PARENTHESIS);

        $lexer = $parser->getLexer();
        if ($lexer->isNextToken(Lexer::T_DISTINCT)) {
            $parser->match(Lexer::T_DISTINCT);

            $this->isDistinct = true;
        }

        $this->expression = $parser->PathExpression(PathExpression::TYPE_STATE_FIELD);
        $parser->match(Lexer::T_COMMA);
        $this->delimiter = $parser->StringPrimary();

        if ($lexer->isNextToken(Lexer::T_ORDER)) {
            $this->orderBy = $parser->OrderByClause();
        }

        $parser->match(Lexer::T_CLOSE_PARENTHESIS);
    }

    /**
     * @param SqlWalker $sqlWalker
     *
     * @return string
     */
    public function getSql(SqlWalker $sqlWalker): string
    {
        return \sprintf('string_agg(%s%s, %s%s)',
            ($this->isDistinct ? 'DISTINCT ' : ''),
            $sqlWalker->walkPathExpression($this->expression),
            $sqlWalker->walkStringPrimary($this->delimiter),
            ($this->orderBy ? $sqlWalker->walkOrderByClause($this->orderBy) : '')
        );
    }
}