Add link url field formatter

Ditto what I said here about this approach in component-based theming. Even outside of that though, this is a really common use-case with needed support.

Super nice!

1. +++ b/core/modules/link/src/Plugin/Field/FieldFormatter/LinkUrlFormatter.php
   @@ -0,0 +1,68 @@
   +/**
   + * @file
   + * Contains \Drupal\image\Plugin\Field\FieldFormatter\ImageUrlFormatter.
   + */
   

   no longer needed

2. +++ b/core/modules/link/src/Plugin/Field/FieldFormatter/LinkUrlFormatter.php
   @@ -0,0 +1,68 @@
   +/**
   + * Plugin implementation of the 'image_url' formatter.
   

   nitpick: wrong docs

3. +++ b/core/modules/link/src/Plugin/Field/FieldFormatter/LinkUrlFormatter.php
   @@ -0,0 +1,68 @@
   +      // Generate external URL without cacheable metadata or internal URL and
   +      // collect cacheable metadata.
   +      if ($link_url->isExternal()) {
   +        $url = $link_url->toString(FALSE);
   +      }
   +      else {
   +        $generated_url = $link_url->toString(TRUE);
   +        $url = $generated_url->getGeneratedUrl();
   +        $cacheable_metadata = CacheableMetadata::createFromObject($generated_url);
   +      }
   

   I guess we could simplify this by always extracting the cacheability metadata. It would just be empty for the external case

Trying to address #5.

+++ b/core/modules/link/src/Plugin/Field/FieldFormatter/LinkUrlFormatter.php
@@ -33,34 +23,26 @@ class LinkUrlFormatter extends LinkFormatter {
    */
   public function settingsSummary() {
-    return array();
+    return [];
   }
...
-    $elements = array();
+    $elements = [];
     $cacheable_metadata = NULL;

Unnecessary change

I've noticed that:

PHP >= 5.4 the short array syntax seems to be the de-facto standard. Only use array(), if you want your script to run on PHP <5.4.

Anyway changed to old 'array()' instead of '[]'.

@dawehner I think we are only using the short array syntax, not? https://www.drupal.org/docs/develop/standards/coding-standards#array

In this case patch #6 looks better.

Made changes as suggested in comment #10

@dawehner I think we are only using the short array syntax, not?

Right, but my comment is 5 months old :)

@Pavan B S it seems your patch files were created against the wrong branch. Review this: Making a Drupal patch with Git and Creating an interdiff

I marked #6 for retest.

Patch #6 looks good. I marked it for retest, just in case it needs a re-roll again.

Looks like #6 is the "correct" patch to review here. As the issue tags say "needs tests" - well it needs tests.

Here's a patch with a test added for the URL field formatter!

2806199-21-add-link-url-field-formatter.patch

Here's a commit showing what putting it to use looks like in a template, with a no-cruft field template and generous use of Twig's ability to remove whitespace.

We don't need an additional field formatter. We can set "URL only" and "Show URL as plain text" for the default link formatter. It returns the URL of a link.