UpdateManagerInstall::buildForm

public UpdateManagerInstall::buildForm(array $form, FormStateInterface $form_state)

public function buildForm(array $form, FormStateInterface $form_state) {
  $this->moduleHandler->loadInclude('update', 'inc', 'update.manager');
  if (!_update_manager_check_backends($form, 'install')) {
    return $form;
  }

  $form['help_text'] = array(
    '#prefix' => '<p>',
    '#markup' => $this->t('You can find <a href=":module_url">modules</a> and <a href=":theme_url">themes</a> on <a href=":drupal_org_url">drupal.org</a>. The following file extensions are supported: %extensions.', array(
      ':module_url' => 'https://www.drupal.org/project/modules',
      ':theme_url' => 'https://www.drupal.org/project/themes',
      ':drupal_org_url' => 'https://www.drupal.org',
      '%extensions' => archiver_get_extensions(),
    )),
    '#suffix' => '</p>',
  );

  $form['project_url'] = array(
    '#type' => 'url',
    '#title' => $this->t('Install from a URL'),
    '#description' => $this->t('For example: %url', array('%url' => 'http://ftp.drupal.org/files/projects/name.tar.gz')),
  );

  $form['information'] = array(
    '#prefix' => '<strong>',
    '#markup' => $this->t('Or'),
    '#suffix' => '</strong>',
  );

  $form['project_upload'] = array(
    '#type' => 'file',
    '#title' => $this->t('Upload a module or theme archive to install'),
    '#description' => $this->t('For example: %filename from your local computer', array('%filename' => 'name.tar.gz')),
  );

  $form['actions'] = array('#type' => 'actions');
  $form['actions']['submit'] = array(
    '#type' => 'submit',
    '#button_type' => 'primary',
    '#value' => $this->t('Install'),
  );

  return $form;
}