fix: #3301239 Improve the error message thrown in PoStreamReader::readLine()...

   *   If the URI is not yet set.

   */

  public function open() {

    if (!empty($this->uri)) {

      $this->fd = fopen($this->uri, 'rb');

      $this->readHeader();

    }

    else {

    if (empty($this->uri)) {

      throw new \Exception('Cannot open stream without URI set.');

    }

    $this->fd = @fopen($this->uri, 'rb');

    if (!$this->fd) {

      throw new \RuntimeException('Cannot open stream for uri ' . $this->uri);

    }

    $this->readHeader();

  }

  /**

<?php

declare(strict_types=1);

namespace Drupal\Tests\Component\Gettext;

use Drupal\Component\Gettext\PoStreamReader;

use PHPUnit\Framework\Attributes\Group;

use PHPUnit\Framework\TestCase;

/**

 * Unit tests for the Gettext PO file header handling features.

 *

 * @see Drupal\Component\Gettext\PoHeader.

 */

#[Group('Gettext')]

class PoStreamReaderTest extends TestCase {

  /**

   * Validates that calling open with an invalid URI throws an exception.

   */

  public function testOpeningFileError(): void {

    $reader = new PoStreamReader();

    $reader->setURI('fake');

    $this->expectException(\RuntimeException::class);

    $this->expectExceptionMessage('Cannot open stream for uri fake');

    $reader->open();

  }

}