php-parser/lib/PhpParser/Lexer/TokenEmulator/FlexibleDocStringEmulator.php

<?php declare(strict_types=1);

namespace PhpParser\Lexer\TokenEmulator;

use PhpParser\Lexer\Emulative;

final class FlexibleDocStringEmulator extends TokenEmulator
{
    const FLEXIBLE_DOC_STRING_REGEX = <<<'REGEX'
/<<<[ \t]*(['"]?)([a-zA-Z_\x80-\xff][a-zA-Z0-9_\x80-\xff]*)\1\r?\n
(?:.*\r?\n)*?
(?<indentation>\h*)\2(?![a-zA-Z0-9_\x80-\xff])(?<separator>(?:;?[\r\n])?)/x
REGEX;

    public function getPhpVersion(): string
    {
        return Emulative::PHP_7_3;
    }

    public function isEmulationNeeded(string $code) : bool
    {
        return strpos($code, '<<<') !== false;
    }

    public function emulate(string $code, array $tokens): array
    {
        // Handled by preprocessing + fixup.
        return $tokens;
    }

    public function reverseEmulate(string $code, array $tokens): array
    {
        // Not supported.
        return $tokens;
    }

    public function preprocessCode(string $code, array &$patches): string {
        if (!preg_match_all(self::FLEXIBLE_DOC_STRING_REGEX, $code, $matches, PREG_SET_ORDER|PREG_OFFSET_CAPTURE)) {
            // No heredoc/nowdoc found
            return $code;
        }

        // Keep track of how much we need to adjust string offsets due to the modifications we
        // already made
        $posDelta = 0;
        foreach ($matches as $match) {
            $indentation = $match['indentation'][0];
            $indentationStart = $match['indentation'][1];

            $separator = $match['separator'][0];
            $separatorStart = $match['separator'][1];

            if ($indentation === '' && $separator !== '') {
                // Ordinary heredoc/nowdoc
                continue;
            }

            if ($indentation !== '') {
                // Remove indentation
                $indentationLen = strlen($indentation);
                $code = substr_replace($code, '', $indentationStart + $posDelta, $indentationLen);
                $patches[] = [$indentationStart + $posDelta, 'add', $indentation];
                $posDelta -= $indentationLen;
            }

            if ($separator === '') {
                // Insert newline as separator
                $code = substr_replace($code, "\n", $separatorStart + $posDelta, 0);
                $patches[] = [$separatorStart + $posDelta, 'remove', "\n"];
                $posDelta += 1;
            }
        }

        return $code;
    }
}