Make datatype callback handling more flexible

+++ b/core/modules/forum/config/rdf.mapping.node.forum.yml
@@ -16,13 +16,15 @@ fieldMappings:
+    datatype_callback:
+      method: 'date_iso8601'

I understand the key 'method' is used because we're typically expecting a class method here, but date_iso8601() is a function. Should we use the key 'callable' instead?

Could we have this patch rerolled to not include other patches so it can possibly be committed before the other patches? It looks good otherwise, and both Drupal\rdf\SchemaOrgDataConverter::interactionCount and Drupal\rdf\CommonDataConverter::rawValue are tested.

+++ b/core/modules/rdf/lib/Drupal/rdf/SchemaOrgDataConverter.php
@@ -16,14 +15,19 @@ class SchemaOrgDataConverter {
+   * @param array $args
+   *   An array of arguments defined in the mapping.
+   *   Expected keys are:
+   *     - interaction_type: The string to use for the type of interaction
+   *       (e.g. UserComments).
    *
    * @return string
    *   The formatted string.
    *
    * @see http://schema.org/UserInteraction
-   * @todo Support other interaction types, see https://drupal.org/node/2020001
    */
-  static function interactionCount($count) {
-    return "UserComment:$count";
+  static function interactionCount($count, $args) {

Could '$arguments' be used here instead of '$args' in order to be consistent with the naming used in the YAML file and the rest of the patch? (for example below)

+++ b/core/modules/rdf/rdf.module
@@ -174,8 +178,9 @@ function rdf_rdfa_attributes($mapping, $data = NULL) {
+          $callback = $mapping['datatype_callback']['callable'];
+          $arguments = isset($mapping['datatype_callback']['arguments']) ? $mapping['datatype_callback']['arguments'] : NULL;
+          $attributes['content'] = call_user_func($callback, $data, $arguments);

Makes the requested change to use $arguments instead of $args in SchemaOrgDataConverter.php.

This looks good with this change.

Committed e9ca0d8 and pushed to 8.x. Thanks!

Writing the change notices.

API change notification

Summary

• Datatype callbacks are used to convert a field value to a specific format for machine processing. We accept arguments to this callback in addition to the value. For instance, instead of hard-coding UserComments UserInteraction into RDF module's Schema.org Data Converter callback, we pass it in as an argument with the key 'interaction_type'.
• You may use any of the UserInteraction types as the 'interaction_type' argument to the datatype_callback callable method or function 'Drupal\rdf\SchemaOrgDataConverter::interactionCount'.

Configuration example

In Drupal 7 this was defined in hook_rdf_mapping(). In Drupal 8, this goes in the YAML for a content type. For instance, a created at field and a comment count:

Before

/**
 * Implements hook_rdf_mapping().
 */
function node_rdf_mapping() {
  return array(
    array(
// ...
        'created' => array(
          'predicates' => array('dc:date', 'dc:created'),
          'datatype' => 'xsd:dateTime',
          'callback' => 'date_iso8601',
        ),
// ...
        'comment_count' => array(
          'predicates' => array('sioc:num_replies'),
          'datatype' => 'xsd:integer',
        ),
// ...
      ),
    ),
  );
}

After

  created:
    properties:
      - 'schema:dateCreated'
    datatype_callback:
      callable: 'date_iso8601'

and

  comment_count:
    properties:
      - 'schema:interactionCount'
    datatype_callback:
      callable: 'Drupal\rdf\SchemaOrgDataConverter::interactionCount'
      arguments:
        interaction_type: 'UserComments'

#2083415: [META] Write up all outstanding change notices before release.

Added a change notice: https://drupal.org/node/2159855

First time doing one of those, please review!

Further edits can be made if necessary but that looks good to me @mlncn, thanks! Closing out this issue.

Actually marking as fixed this time :)