Issue #3478628 by oily, alexpott, catch, sheshsharma, osopolar, dunx, shane...

  public function listInfo() {

    if (!isset($this->list)) {

      $this->list = [];

      $installed_themes = $this->configFactory->get('core.extension')->get('theme');

      $installed_themes = array_keys($this->configFactory->get('core.extension')->get('theme'));

      if (!empty($installed_themes)) {

        $list = $this->themeList->getList();

        foreach (array_keys($installed_themes) as $theme_name) {

          $this->addTheme($list[$theme_name]);

        foreach ($installed_themes as $theme) {

          // Do not add installed themes that cannot be found by the

          // extension.list.theme service. If a theme does go missing from the

          // file system any call to ::getTheme() will result in an exception

          // and an error being logged. Ignoring the problem here allows the

          // theme system to fix itself while updating.

          if (isset($list[$theme])) {

            $this->addTheme($list[$theme]);

          }

        }

      }

    }

    $this->configFactory = $this->getConfigFactoryStub([

      'core.extension' => [

        'module' => [],

        'theme' => [],

        'theme' => ['stark' => 'stark'],

        'disabled' => [

          'theme' => [],

        ],

    }

  }

  /**

   * Test that a missing theme doesn't break ThemeHandler::listInfo().

   *

   * @covers ::listInfo

   */

  public function testMissingTheme(): void {

    $themes = $this->themeHandler->listInfo();

    $this->assertSame([], $themes);

  }

}

/**