What is the best practice for writing a link to the screen through t()?

Question

In Drupal 7, one could do the following one line::

t('Visit !mylink', ['!mylink' => l('my website', 'http://example.com')]);

But that no longer works in Drupal 8 or 9 😞. So far, I've tried this:

First I create a link, Drupal 8 style:

$mylink = Link::fromTextAndUrl('my website', Url::fromUri('http://example.com'));

Then try to create a string that can be printed. I've tried toString():

t('Visit @mylink', ['@mylink' => $mylink->toString()]);

However, we're not supposed to do this. The API docs says:

Do not use this method to render a link in an HTML context. In an HTML context, self::toRenderable() should be used so that render cache information is maintained.

So I try to use toRenderable():

t('Visit @mylink', ['@mylink' => render($mylink->toRenderable()]);

But PHP 7.2 doesn't like it. The call to t() produces the following Notice:

Notice: Only variables should be passed by reference ...

Fair enough - but how is this done?

I could not find how to do this described in any of the obvious docs, such as:

• https://www.drupal.org/docs/security-in-drupal/sanitizing-output
• https://www.drupal.org/docs/security-in-drupal/writing-secure-code-for-drupal

So my question is:
What is the best practice for writing a link to the screen in Drupal 8?

(Environment: Ubuntu 20.04 LTS, Drupal 8.8.6 (core + devel), procedural code - e.g. hook_help()).

Answer 1

For a link enclosed in translatable text, Drupal core suggests to use t() and embed the HTML anchor tag directly in the translated string. In LinkGeneratorInterface::generate(), the example code for this case is the following.

$text = t('Visit the <a href=":url">content types</a> page', array(
  ':url' => Url::fromRoute('entity.node_type.collection')->toString(),
));

Searching for :url in the Drupal core code finds code like the following.

BlockContentController::add()

if (count($types) === 0) {
  return [
    '#markup' => $this
      ->t('You have not created any block types yet. Go to the <a href=":url">block type creation page</a> to add a new block type.', [
      ':url' => Url::fromRoute('block_content.type_add')->toString(),
    ]),
  ];
}

ListingEmpty::render()

  $element = [
    '#markup' => $this->t('Add a <a href=":url">custom block</a>.', [
      ':url' => Url::fromRoute('block_content.add_page')->toString(),
    ]),
    '#access' => $access_result->isAllowed(),
    '#cache' => [
      'contexts' => $access_result->getCacheContexts(),
      'tags' => $access_result->getCacheTags(),
      'max-age' => $access_result->getCacheMaxAge(),
    ],
  ];

Alternatively, Drupal core uses the following code.

block_help()

$themes = \Drupal::service('theme_handler')->listInfo();
$output = '<p>' . t('Block placement is specific to each theme on your site. Changes will not be saved until you click <em>Save blocks</em> at the bottom of the page.') . '</p>';
$output .= '<p>' . Link::fromTextAndUrl(t('Demonstrate block regions (@theme)', [
  '@theme' => $themes[$demo_theme]->info['name'],
]), Url::fromRoute('block.admin_demo', ['theme' => $demo_theme]))->toString() . '</p>';

template_preprocess_forums()

    if ($variables['tid'] != $topic->forum_tid) {
      $variables['topics'][$id]->moved = TRUE;
      $variables['topics'][$id]->title = $topic->getTitle();
      $variables['topics'][$id]->message = Link::fromTextAndUrl(t('This topic has been moved'), Url::fromRoute('forum.page', ['taxonomy_term' => $topic->forum_tid]))->toString();
    }

Answer 2

It will easy if you convert link to url and use translate like this.

$url = Url::fromUri('http://example.com')->toString();
t('Visit <a href=":href">link</a>', array(':href' => $url));

Example drupal core use translation with link.

$requirements['online'] = array(
      'title' => t('Internet'),
      'value' => t('The translation server is offline.'),
      'severity' => REQUIREMENT_ERROR,
      'description' => t('The installer requires to contact the translation server to download a translation file. Check your internet connection and verify that your website can reach the translation server at <a href=":server_url">@server_url</a>.', array(
        ':server_url' => $server_url,
        '@server_url' => $server_url,
      )),
    );