merged CER submodule

sites/all/modules/contrib/fields/cer/LICENSE.txt

@@ -0,0 +1,339 @@
+                    GNU GENERAL PUBLIC LICENSE
+                       Version 2, June 1991
+
+ Copyright (C) 1989, 1991 Free Software Foundation, Inc.,
+ 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ Everyone is permitted to copy and distribute verbatim copies
+ of this license document, but changing it is not allowed.
+
+                            Preamble
+
+  The licenses for most software are designed to take away your
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+Foundation's software and to any other program whose authors commit to
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+   TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION
+
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+
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+  `Gnomovision' (which makes passes at compilers) written by James Hacker.
+
+  <signature of Ty Coon>, 1 April 1989
+  Ty Coon, President of Vice
+
+This General Public License does not permit incorporating your program into
+proprietary programs.  If your program is a subroutine library, you may
+consider it more useful to permit linking proprietary applications with the
+library.  If this is what you want to do, use the GNU Lesser General
+Public License instead of this License.

sites/all/modules/contrib/fields/cer/README.txt

@@ -0,0 +1,58 @@
+ACKNOWLEDGEMENTS
+
+As this is the next evolution of Corresponding Node References,
+I would like to say thanks for all the work done over on Corresponding Node
+References.
+
+DESCRIPTION
+
+It syncs the entity reference between two entity types which have an entity
+reference to each other, so double editing entities is no longer needed. If one
+entity has a reference, the other entity also receives a reference to the saved
+entity if it is referenced in that entity.
+
+DEPENDENCIES
+
+7.x: Entity Reference
+
+EXAMPLE
+
+Entity type A has an entity reference to entity type B and entity type B has an
+entity reference to entity type A. When you create entity X of type A and
+reference it to entity Y of type B entity Y will also receive an update in its
+entity reference field pointing to entity X.
+
+KNOWN ISSUES
+
+- Support for entity reference fields in field collections is still a work in progress.
+  CER has no native support for entities that are wrapped by other entities (i.e.,
+  field collections), and implementing this properly will require extensive changes
+  to many parts of CER. For this reason, field collection support is on hold until
+  a few other major issues in the queue are sorted out. The thread for field collection
+  support is http://drupal.org/node/1729666.
+
+- Support for multi-language entities is, at the time of this writing, flaky at best.
+  There is a patch to implement better multi-language support, available at
+  http://drupal.org/node/1961026. If this patch works well for you, PLEASE post
+  in that issue to say that it worked so that the patch can be reviewed by
+  the community before being committed into CER.
+
+- If you're updating CER from 1.x to 2.x, you should rebuild your theme registry.
+  This is because the reference labels on CER's admin page were made themeable
+  in 2.x, so you'll need to make Drupal recognize the new theme hook.
+
+INSTALL
+
+- To install enable the module at admin/build/modules
+- Create entity type A
+- Create entity type B
+- Create a entity reference field on entity type A pointing to entity B
+- Create a entity reference field on entity type B pointing to entity A
+- Go to the settings page at admin/config/system/cer. 
+  Select to enable the corresponding referencing for these node types pointing 
+  to each other.
+- Create some entities and reference them to each other
+
+MAINTAINER
+
+Questions, comments, etc. should be directed to phenaproxima (djphenaproxima@gmail.com).

sites/all/modules/contrib/fields/cer/cer.admin.inc

@@ -0,0 +1,253 @@
+<?php
+
+/**
+ * @file
+ * Administrative functionality, separated for performance purposes.
+ */
+
+/**
+ * The settings form.
+ */
+function cer_settings_form($form = array(), &$form_state) {
+  $channels = array();
+
+  foreach (_cer_get_fields() as $field) {
+    foreach ($field['bundles'] as $entity_type => $bundles) {
+      foreach ($bundles as $bundle) {
+        $instance = field_info_instance($entity_type, $field['field_name'], $bundle);
+        $channels = array_merge($channels, _cer_find_channels($instance));
+       }
+     }
+   }
+
+  if (empty($channels)) {
+    drupal_set_message(t('There are no entity reference fields that can correspond.'), 'warning');
+  }
+  else {
+    $mapping = array();
+    foreach ($channels as $count => $key) {
+      $formatted_key = str_replace(' ', '*', $key);
+
+      $mapping[$count] = $formatted_key;
+
+      $form['values']["enabled_{$count}"] = array(
+        '#type' => 'checkbox',
+        '#default_value' => cer_preset_enabled($formatted_key),
+        '#title' => theme('cer_label', array('key' => $key)),
+      );
+    }
+
+    // We are using a hidden field to submit the configuration because on
+    // some systems the checkbox name length is limited, and using
+    // the key would cause the length to be too long. (Issue #558612)
+    $form['mapping'] = array(
+      '#type' => 'hidden',
+      '#value' => serialize($mapping),
+    );
+
+    $form['submit'] = array(
+      '#type' => 'submit',
+      '#value' => t('Save'),
+    );
+  }
+
+
+  return $form;
+}
+
+/**
+ * Submit function for settings form.
+ */
+function cer_settings_form_submit($form, $form_state) {
+  ctools_include('export');
+  $query_values = array();
+
+  $mapping = unserialize($form_state['values']['mapping']);
+
+  foreach ($form_state['values'] as $key => $value) {
+    $keys = explode('_', $key);
+    if ($keys[0] == 'enabled') {
+      $query_values[$mapping[$keys[1]]] = $value;
+    }
+  }
+
+  // load all existing presets
+  $presets = ctools_export_crud_load_all('cer');
+
+  foreach ($query_values as $key => $value) {
+    // get preset object (create new one if it doesn't exist already).
+    $preset = empty($presets[$key]) ? ctools_export_crud_new('cer') : $presets[$key];
+
+    // set and save value
+    if (empty($preset->entity_types_content_fields)) {
+      $preset->entity_types_content_fields = $key;
+    }
+    $preset->enabled = $value;
+    ctools_export_crud_save('cer', $preset);
+
+    // remove from list of presets, so we know which ones are still used
+    if (isset($presets[$key])) {
+      unset($presets[$key]);
+    }
+  }
+
+  drupal_set_message(t('The configuration has been saved.'));
+}
+
+/**
+ * Allows batch updating of existing entities.
+ */
+function cer_update_form($form = array(), &$form_state) {
+  $form['type'] = array(
+    '#type' => 'select',
+    '#title' => t('Entity type'),
+    '#required' => TRUE,
+    '#options' => array(),
+    '#description' => t('Select the entity type that you want to update.'),
+  );
+  foreach (entity_get_info() as $type => $class) {
+    $form['type']['#options'][$type] = $class['label'];
+  }
+
+  $form['submit'] = array(
+    '#type' => 'submit',
+    '#value' => t('Submit'),
+  );
+
+  return $form;
+}
+
+/**
+ * The update form.
+ * Allows updating of current entitys.
+ */
+function cer_update_form_submit($form, &$form_state) {
+  $batch = array(
+    'finished' => 'cer_batch_update_existing_finished',
+    'title' => t('Processing'),
+    'init_message' => t('Preparing to update corresponding entity references for existing entities...'),
+    'progress_message' => t('Processing entities...'),
+    'error_message' => t('Corresponding entity references - existing entity update has encountered an error.'),
+  );
+
+  $entities = entity_load($form_state['values']['type'], FALSE);
+  foreach ($entities as $entity) {
+    $batch['operations'][] = array('cer_processing_entity', array('update', $entity, $form_state['values']['type']));
+  }
+  batch_set($batch);
+}
+
+/**
+ * The purpose of this function is to answer this question: I am a field instance. Which other
+ * fields reference the entity that owns me? And of those instances, which ones can I reference?
+ * The answer is returned as an array of CER keys: "entity1 bundle1 field1 entity2 bundle2 field2".
+ *
+ * @param array $instance
+ *  Field instance info, as returned by field_info_instance().
+ *
+ * @return array
+ */
+function _cer_find_channels($instance) {
+  $channels = array();
+
+  $my_id = $instance['entity_type'] . ' ' . $instance['bundle'] . ' ' . $instance['field_name'];
+  $my_info = field_info_field($instance['field_name']);
+  $my_targets = _cer_get_target_bundles($my_info);
+  $my_target_type = $my_info['settings']['target_type'];
+
+  $referrers = _cer_find_referrers($instance['entity_type'], $instance['bundle']);
+  foreach ($referrers as $referrer) {
+    if (isset($referrer['bundles'][$my_target_type])) {
+      if (empty($my_targets)) {
+        $bundles = $referrer['bundles'][$my_target_type];
+      }
+      else {
+        $bundles = array_intersect($referrer['bundles'][$my_target_type], $my_targets);
+      }
+      
+      foreach ($bundles as $bundle) {
+        $channels[] = "{$my_id} {$my_target_type} {$bundle} " . $referrer['field_name'];
+      }
+    }
+  }
+
+  return $channels;
+}
+
+/**
+ * Find all fields that can reference the given entity type and bundle.
+ *
+ * @param $entity_type
+ *  The entity type that can be referenced.
+ * @param $bundle
+ *  The bundle that can be referenced.
+ *
+ * @return array
+ */ 
+function _cer_find_referrers($entity_type, $bundle) {
+  $referrers = array();
+  foreach (_cer_get_fields() as $field) {
+    if ($field['settings']['target_type'] == $entity_type) {
+      $target_bundles = _cer_get_target_bundles($field);
+      if (empty($target_bundles) || in_array($bundle, $target_bundles)) {
+        $referrers[] = $field;
+      }
+    }
+  }
+
+  return $referrers;
+}
+
+/**
+ * Find all bundles reference-able by a given field. If all bundles are reference-able,
+ * an empty array is returned.
+ *
+ * @param $field
+ *  Field info array as returned by field_info_field().
+ *
+ * @return array
+ */
+function _cer_get_target_bundles($field) {
+  $target_bundles = array();
+
+  // If the reference field is using a view, load the view and see if it's filtering by the entity
+  // type's bundle filter. If it is, the filter values are the target bundles. Otherwise,
+  // assume that all bundles can be referenced.
+  //
+  // @todo Support contextual filters?
+  //
+  // NOTE: Selection handlers (i.e., $field['settings']['handler']) are plugins owned by
+  // Entity Reference. There is no method defined to get an array of referenceable
+  // bundles, but hopefully, if CER gains enough traction in the community, such a
+  // method can be added to the EntityReference_SelectionHandler interface. This
+  // function could then be deprecated, which would be a more flexible, future-proof
+  // method of finding a field's target bundles.
+  //
+  if ($field['settings']['handler'] == 'views') {
+    $view = views_get_view($field['settings']['handler_settings']['view']['view_name']);
+    $view->set_display($field['settings']['handler_settings']['view']['display_name']);
+
+    $info = entity_get_info($field['settings']['target_type']);
+    if ($info['entity keys']['bundle'] && $handler = $view->display_handler->get_handler('filter', $info['entity keys']['bundle'])) {
+      $target_bundles = $handler->value;
+    }
+  }
+  else {
+    $target_bundles = $field['settings']['handler_settings']['target_bundles'];
+  }
+
+  return $target_bundles;
+}
+
+/**
+ * Get the Field API definitions for all entity reference fields.
+ *
+ * @return array
+ */
+function _cer_get_fields() {
+  static $fields;
+  if (!isset($fields)) {
+    $fields = array_map('field_info_field', db_select('field_config', 'fc')->fields('fc', array('field_name'))->condition('type', 'entityreference')->execute()->fetchCol());
+  }  
+  return $fields;
+}

sites/all/modules/contrib/fields/cer/cer.info

@@ -0,0 +1,16 @@
+name = Corresponding Entity References
+description = Syncs the entity references between entity types which have an entityreference to each other.
+core = 7.x
+package = Fields
+dependencies[] = entityreference
+dependencies[] = ctools
+
+files[] = handler.inc
+
+configure = admin/config/system/cer
+; Information added by drupal.org packaging script on 2013-05-01
+version = "7.x-2.x-dev"
+core = "7.x"
+project = "cer"
+datestamp = "1367412087"
+

sites/all/modules/contrib/fields/cer/cer.install

@@ -0,0 +1,41 @@
+<?php
+
+/**
+ * @file
+ * Install file providing corresponding entity reference schema.
+ */
+
+/**
+ * Implements hook_schema().
+ */
+function cer_schema() {
+  $schema['cer'] = array(
+    'description' => t('Saves the content types and entity reference fields for which the corresponding entity reference is enabled'),
+    'fields' => array(
+      'entity_types_content_fields' => array('type' => 'varchar', 'length' => 200, 'not null' => TRUE, 'default' => ''),
+      'enabled' => array('type' => 'int', 'unsigned' => TRUE, 'not null' => TRUE, 'default' => 0),
+    ),
+    'primary key' => array('entity_types_content_fields'),
+    'export' => array(
+      'key' => 'entity_types_content_fields',
+      'status' => 'enabled',
+      'primary key' => 'entity_types_content_fields',
+      'key name' => 'Corresponding entity reference',
+      'identifier' => 'cnr_obj',
+      'api' => array(
+        'api' => 'default_cer_presets',
+        'owner' => 'cer',
+        'minimum_version' => 1,
+        'current_version' => 1,
+      ),
+    ),
+  );
+  return $schema;
+}
+
+/**
+ * Rename table to shorten module name.
+ */
+function cer_update_7001() {
+  db_rename_table('corresponding_entity_references', 'cer');
+}

sites/all/modules/contrib/fields/cer/cer.module

@@ -0,0 +1,300 @@
+<?php
+
+/**
+ * @file
+ * Main module file.
+ */
+
+/**
+ * Implements hook_menu().
+ */
+function cer_menu() {
+  $items = array();
+
+  $items['admin/config/system/cer'] = array(
+    'title' => 'Corresponding entity references',
+    'page callback' => 'drupal_get_form',
+    'page arguments' => array('cer_settings_form'),
+    'access arguments' => array('administer cer settings'),
+    'file' => 'cer.admin.inc',
+    'type' => MENU_NORMAL_ITEM,
+  );
+  $items['admin/config/system/cer/references'] = array(
+    'title' => 'References',
+    'page callback' => 'drupal_get_form',
+    'page arguments' => array('cer_settings_form'),
+    'access arguments' => array('administer cer settings'),
+    'file' => 'cer.admin.inc',
+    'type' => MENU_DEFAULT_LOCAL_TASK,
+  );
+  $items['admin/config/system/cer/update'] = array(
+    'title' => 'Update existing entities',
+    'page callback' => 'drupal_get_form',
+    'page arguments' => array('cer_update_form'),
+    'access arguments' => array('administer cer settings'),
+    'file' => 'cer.admin.inc',
+    'type' => MENU_LOCAL_TASK,
+  );
+
+  return $items;
+}
+
+/**
+ * Implements hook_permission().
+ */
+function cer_permission() {
+  return array(
+    'administer cer settings' => array(
+      'title' => t('Administer corresponding entity reference settings'),
+    )
+  );
+}
+
+/**
+ * Implements hook_help().
+ */
+function cer_help($path, $arg) {
+  $output = '';
+  if ($path == 'admin/config/system/cer') {
+    $output .= t('Check which entity references should listen to each other. When checking a check box a reference on entity type A to entity B will automatically update the entity reference field on entity B adding an entry which points to entity A.');
+  }
+  elseif ($path == 'admin/config/system/cer/update') {
+    $output .= t('This will update all the existing entities for the selected content types so that their entity reference fields are in sync.');
+    $output .= '<br />';
+    $output .= t('This process may take a long time depending on the number of entities you are updating.');
+    $output .= '<br /><br />';
+    $output .= t('When the process is finished you will see a count of the number of entities that were updated.');
+  }
+  return $output;
+}
+
+/**
+ * Implements hook_field_delete_instance().
+ */
+function cer_field_delete_instance($instance) {
+  foreach (cer_preset_load_enabled() as $row) {
+    $keys = explode('*', $row->entity_types_content_fields);
+
+    if (($keys[0] == $instance['entity_type'] && $keys[1] == $instance['bundle'] && $keys[2] == $instance['field_name']) || ($keys[3] == $instance['entity_type'] && $keys[4] == $instance['bundle'] && $keys[5] == $instance['field_name'])) {
+      cer_preset_delete($row->entity_types_content_fields);
+    }
+  }
+}
+
+/**
+ * Implements hook_field_delete_field().
+ */
+function cer_field_delete_field($field) {
+  foreach (cer_preset_load_enabled() as $row) {
+    $keys = explode('*', $row->entity_types_content_fields);
+
+    if ($keys[2] == $field['field_name'] || $keys[5] == $field['field_name']) {
+      cer_preset_delete($row->entity_types_content_fields);
+    }
+  }
+}
+
+/**
+ * Implements hook_theme().
+ */
+function cer_theme() {
+  return array(
+    'cer_label' => array(
+      'variables' => array('key' => ''),
+    ),
+  );
+}
+
+function theme_cer_label($variables) {
+  $key = explode(' ', $variables['key']);
+  
+  $local = field_info_instance($key[0], $key[2], $key[1]);
+  $remote = field_info_instance($key[3], $key[5], $key[4]);
+
+  $message = 'Correspond <span title="!local_field">%local_label</span> on !local_entity(s) of type %local_bundle with <span title="!remote_field">%remote_label</span> on !remote_entity(s) of type %remote_bundle.';
+
+  $variables = array(
+    '%local_label' => $local['label'],
+    '!local_field' => $local['field_name'],
+    '!local_entity' => $local['entity_type'],
+    '%local_bundle' => $local['bundle'],
+    '%remote_label' => $remote['label'],
+    '!remote_field' => $remote['field_name'],
+    '!remote_entity' => $remote['entity_type'],
+    '%remote_bundle' => $remote['bundle'],
+  );
+
+  return t($message, $variables);
+}
+
+/**
+ * Implements hook_entity_insert().
+ */
+function cer_entity_insert($entity, $type) {
+  cer_processing_entity('insert', $entity, $type);
+}
+
+/**
+ * Implements hook_entity_update().
+ */
+function cer_entity_update($entity, $type) {
+  cer_processing_entity('update', $entity, $type);
+}
+
+/**
+ * Implements hook_entity_delete().
+ */
+function cer_entity_delete($entity, $type) {
+  cer_processing_entity('delete', $entity, $type);
+}
+
+/**
+ * Load enabled CER presets.
+ */
+function cer_preset_load_enabled() {
+  ctools_include('export');
+  return ctools_export_load_object('cer', 'conditions', array('enabled' => 1));
+}
+
+/**
+ * Return CER preset by key.
+ */
+function cer_preset_load($key) {
+  ctools_include('export');
+  return ctools_export_crud_load('cer', $key);
+}
+
+/**
+ * Return 1 if CER preset specified by given key is enabled.
+ */
+function cer_preset_enabled($key) {
+  $preset = cer_preset_load($key);
+  return empty($preset) ? 0 : $preset->enabled;
+}
+
+/**
+ * Deletes or disables a given CER preset.
+ */
+function cer_preset_delete($key) {
+  ctools_include('export');
+
+  ctools_export_crud_delete('cer', $key);
+  ctools_export_crud_disable('cer', $key);
+
+  ctools_export_load_object_reset('cer');
+}
+
+/**
+ * Process a entity's corresponding entity references.
+ *
+ * @param string $op 
+ *  The operation being performed on the entity (insert, update, or delete).
+ *
+ * @param object $entity
+ *  The entity.
+ *
+ * @param string $entity_type
+ *  The entity type.
+ *
+ * @param array $context
+ *  Either the Batch API context (since this is the callback function used
+ *  during bulk update) or NULL if we're not in a batch job.
+ */
+function cer_processing_entity($op, $entity, $entity_type, &$context = NULL) {
+  // If the entity is of the wrong type, entity_extract_IDs() will throw
+  // EntityMalformedException and rightfully bail out here.
+  list (, , $bundle) = entity_extract_IDs($entity_type, $entity);
+
+  $result = cer_preset_load_enabled();
+
+  foreach ($result as $row) {
+    $keys = explode('*', $row->entity_types_content_fields);
+
+    if ($keys[0] == $entity_type && $keys[1] == $bundle) {
+      try {
+        $handler = new CerHandler($row->entity_types_content_fields, $entity);
+        call_user_func(array($handler, $op));
+      }
+      catch (CerException $e) {
+        if (isset($context)) {
+          $context['results']['errors'][] = $e;
+        }
+        else {
+          throw $e;
+        }
+      }
+    }
+
+    if ($keys[3] == $entity_type && $keys[4] == $bundle) {
+      $preset = implode('*', array($keys[3], $keys[4], $keys[5], $keys[0], $keys[1], $keys[2]));
+
+      try {
+        $handler = new CerHandler($preset, $entity);
+        call_user_func(array($handler, $op));
+      }
+      catch (CerException $e) {
+        if (isset($context)) {
+          $context['results']['errors'][] = $e;
+        }
+        else {
+          throw $e;
+        }
+      }
+    }
+  }
+
+  if (isset($context)) {
+    $context['results']['count']++;
+  }
+}
+
+/**
+ * Batch 'finished' callback.
+ */
+function cer_batch_update_existing_finished($success, $results, $operations) {
+  if ($success) {
+    $message = format_plural($results['count'], '1 entity processed.', '@count entities processed.');
+
+    if (isset($results['errors'])) {
+      $type = 'warning';
+      foreach ($results['errors'] as $e) {
+        drupal_set_message($e->getMessage(), 'error');
+      }
+    }
+    else {
+      $type = 'status';
+    }
+    drupal_set_message($message, $type);
+  }
+  else {
+    // An error occurred. $operations contains the operations that remained unprocessed.
+    $error_operation = reset($operations);
+    $message = 'An error occurred while processing ' . $error_operation[0] . ' with arguments:' . print_r($error_operation[0], TRUE);
+    drupal_set_message($message, 'error');
+  }
+}
+
+/**
+ * Implements hook_ctools_plugin_api().
+ */
+function cer_ctools_plugin_api($owner, $api) {
+  if ($owner == 'cer' && $api == 'default_cer_presets') {
+    return array('version' => 1);
+  }
+}
+
+/**
+ * Update field data.
+ *
+ * @param $node the referenced node to be updated.
+ */
+function _cer_update($entity_type, $entity) {
+  $entity->original = isset($entity->original) ? $entity->original : NULL;
+
+  field_attach_presave($entity_type, $entity);
+  field_attach_update($entity_type, $entity);
+
+  $extract_ids = entity_extract_IDs($entity_type, $entity);
+  $id = array_shift($extract_ids);
+  entity_get_controller($entity_type)->resetCache(array($id));
+}

sites/all/modules/contrib/fields/cer/handler.inc

@@ -0,0 +1,437 @@
+<?php
+
+/**
+ * @file
+ * Contains base code for CER handlers, which are objects responsible for
+ * creating, updating and deleting corresponding references between entities.
+ */
+
+/**
+ * Exception related to CER operations.
+ */
+class CerException extends Exception {
+}
+
+interface CerHandlerInterface {
+
+  /**
+   * @constructor
+   *
+   * @param string $preset
+   *  The CER preset string, in the format:
+   *  entity_a*bundle_a*field_a*entity_b*bundle_b*field_b.
+   *
+   * @param $entity.
+   *  The local (home) entity to be wrapped by this instance.
+   */
+  public function __construct($preset, $entity);
+
+  /**
+   * Create reciprocal references on referenced entities after the
+   * local entity has been created.
+   */
+  public function insert();
+
+  /**
+   * Delete reciprocal references on entities the local entity is no
+   * longer referencing, and create new reciprocal references, after
+   * the local entity has been updated.
+   */
+  public function update();
+
+  /**
+   * Delete all reciprocal references after the local entity is deleted.
+   */
+  public function delete();
+  
+  /**
+   * Check if $entity is referenced by the local entity.
+   *
+   * @param object $entity
+   *  The remote entity.
+   *
+   * @return boolean
+   */
+  public function references($entity);
+
+  /**
+   * Check if the local entity is referenced by $entity.
+   *
+   * @param object $entity
+   *  The remote entiy.
+   *
+   * @return boolean
+   */
+  public function referencedBy($entity);
+  
+  /**
+   * Check if the remote entity can reference the local entity, and vice-versa.
+   *
+   * @param object $entity
+   *  The remote entity.
+   *
+   * @return boolean
+   */
+  public function referenceable($entity);
+
+  /**
+   * Create a reference to the local entity on the remote entity, and vice-versa
+   * if needed. Should throw CerException if the reference(s) can't be created
+   * for any reason.
+   *
+   * @param object $entity
+   */
+  public function reference($entity);
+
+  /**
+   * Delete all references to the remote entity from the local entity,
+   * and delete reciprocal references from the remote entity.
+   *
+   * @param object $entity.
+   */
+  public function dereference($entity);
+
+}
+
+/**
+ * @class
+ * Base class for CER handlers. All this does is parse the preset
+ * and store instance info about the local and remote fields.
+ */
+abstract class CerHandlerBase {
+
+  /**
+   * Local field instance definition.
+   */
+  protected $local;
+
+  /**
+   * Remote field instance definition.
+   */
+  protected $remote;
+
+  public function __construct($preset) {
+    $keys = explode('*', $preset);
+
+    if (sizeof($keys) != 6) {
+      throw new CerException(t('Invalid configuration: @preset', array('@preset' => $preset)));
+    }
+
+    $this->local = field_info_instance($keys[0], $keys[2], $keys[1]);
+    if ($this->local) {
+      $this->local['field'] = field_info_field($keys[2]);
+    }
+    else {
+      throw new CerException(t('Local field instance does not exist.'));
+    }
+
+    $this->remote = field_info_instance($keys[3], $keys[5], $keys[4]);
+    if ($this->remote) {
+      $this->remote['field'] = field_info_field($keys[5]);
+    }
+    else {
+      throw new CerException(t('Remote field instance does not exist.'));
+    }
+  }
+
+}
+
+/**
+ * @class
+ * Generic CER handler with rudimentary language handling.
+ */
+class CerHandler extends CerHandlerBase implements CerHandlerInterface {
+
+  /**
+   * The local (home) entity.
+   */
+  protected $entity;
+
+  /**
+   * The local entity's ID.
+   */
+  protected $id;
+
+  /**
+   * Implements CerHandlerInterface::__construct().
+   */
+  public function __construct($preset, $entity) {
+    parent::__construct($preset);
+
+    // If $entity is of the wrong type, entity_extract_IDs()
+    // will throw EntityMalformedException here.
+    $extract_ids = entity_extract_IDs($this->local['entity_type'], $entity);
+    $this->id = array_shift($extract_ids);
+
+    $this->entity = $entity;
+  }
+
+  /**
+   * Implements CerHandlerInterface::insert().
+   */
+  public function insert() {
+    foreach ($this->getReferencedEntities() as $referenced_entity) {
+      $this->reference($referenced_entity);
+      _cer_update($this->remote['entity_type'], $referenced_entity);
+    }
+  }
+
+  /**
+   * Implements CerHandlerInterface::update().
+   */
+  public function update() {
+    $original = isset($this->entity->original) ? $this->entity->original : $this->entity;
+
+    $deleted = array_diff($this->getReferenceIDs($original, $this->local), $this->getLocalReferenceIDs());
+    if ($deleted) {
+      $entities = entity_load($this->remote['entity_type'], $deleted);
+      foreach ($entities as $referenced_entity) {
+        $this->dereference($referenced_entity);
+        _cer_update($this->remote['entity_type'], $referenced_entity);
+      }
+    }
+
+    $this->insert();
+  }
+
+  /**
+   * Implements CerHandlerInterface::delete().
+   */
+  public function delete() {
+    foreach ($this->getReferencedEntities() as $referenced_entity) {
+      $this->dereference($referenced_entity);
+      _cer_update($this->remote['entity_type'], $referenced_entity);
+    }
+  }
+
+  /**
+   * Implements CerHandlerInterface::references().
+   */  
+  public function references($entity) {
+    return in_array($this->getRemoteEntityID($entity), $this->getLocalReferenceIDs());
+  }
+
+  /**
+   * Implements CerHandlerInterface::referencedBy().
+   */
+  public function referencedBy($entity) {
+    return in_array($this->id, $this->getRemoteReferenceIDs($entity));
+  }
+
+  /**
+   * Implements CerHandlerInterface::referenceable().
+   */
+  public function referenceable($entity) {
+    $id = $this->getRemoteEntityID($entity);
+
+    $allowed = array(
+      entityreference_get_selection_handler(
+        $this->local['field'],
+        $this->local,
+        $this->local['entity_type'],
+        $this->entity
+      )
+        ->validateReferencableEntities(array($id)),
+      entityreference_get_selection_handler(
+        $this->remote['field'],
+        $this->remote,
+        $this->remote['entity_type'],
+        $entity
+      )
+        ->validateReferencableEntities(array($this->id)),
+    );
+
+    return in_array($id, $allowed[0]) && in_array($this->id, $allowed[1]);
+  }
+
+  /**
+   * Implements CerHandlerInterface::reference().
+   */
+  public function reference($entity) {
+    if ($this->referenceable($entity)) {
+      try {
+        $this->addReferenceTo($entity);
+      }
+      catch (CerException $e) {
+        // Fail silently
+      }
+    
+      try {
+        $this->addReferenceFrom($entity);
+      }
+      catch (CerException $e) {
+        // Fail silently
+      }
+    }
+    else {
+      throw new CerException(t('Cannot create invalid reference to remote entity.'));
+    }
+  }
+
+  /**
+   * Implements CerHandlerInterface::dereference().
+   */
+  public function dereference($entity) {
+    if ($this->references($entity)) {
+      $id = $this->getRemoteEntityID($entity);
+
+      foreach ($this->entity->{$this->local['field_name']} as $language => $references) {
+        foreach ($references as $delta => $reference) {
+          if ($reference['target_id'] == $id) {
+            unset($this->entity->{$this->local['field_name']}[$language][$delta]);
+          }
+        }
+      }
+    }
+
+    if ($this->referencedBy($entity)) {
+      foreach ($entity->{$this->remote['field_name']} as $language => $references) {
+        foreach ($references as $delta => $reference) {
+          if ($reference['target_id'] == $this->id) {
+            unset($entity->{$this->remote['field_name']}[$language][$delta]);
+          }
+        }
+      }
+    }
+  }
+
+  /**
+   * Creates a reference to the local entity on the remote entity. Throws CerException
+   * if the local entity is already referenced by the remote entity, or if the remote
+   * field cannot hold any more values.
+   *
+   * @param object $entity
+   *  The remote entity.
+   */ 
+  protected function addReferenceFrom($entity) {
+    if ($this->referencedBy($entity)) {
+      throw new CerException(t('Cannot create duplicate reference from remote entity.'));
+    }
+    elseif ($this->filled($this->getRemoteReferenceIDs($entity), $this->remote['field'])) {
+      throw new CerException(t('Remote field cannot support any more references.'));
+    }
+    else {
+      $languages = field_available_languages($this->remote['entity_type'], $this->remote['field']);
+      foreach ($languages as $language) {
+        $entity->{$this->remote['field_name']}[$language][] = array('target_id' => $this->id);
+      }
+    }
+  }
+
+  /**
+   * Creates a reference to the remote entity on the local entity. Throws CerException
+   * if the local entity already references the remote entity, or if the field cannot
+   * hold any more values.
+   *
+   * @param object $entity
+   *  The remote entity.
+   */
+  protected function addReferenceTo($entity) {
+    $id = $this->getRemoteEntityID($entity);
+
+    if ($this->references($entity)) {
+      throw new CerException(t('Cannot create duplicate reference to remote entity.'));
+    }
+    elseif ($this->filled($this->getLocalReferenceIDs(), $this->local['field'])) {
+      throw new CerException(t('Local field cannot support any more references.'));
+    }
+    else {
+      $languages = field_available_languages($this->local['entity_type'], $this->local['field']);
+      foreach ($languages as $language) {
+        $this->entity->{$this->local['field_name']}[$language][] = array('target_id' => $id);
+      }
+    }
+  }
+
+  /**
+   * Get the ID of the remote entity. If the entity is of the wrong type,
+   * EntityMalformedException will be thrown.
+   *
+   * @param object $entity
+   *  The remote entity.
+   *
+   * @return mixed
+   *  The remote entity ID.
+   */
+  protected function getRemoteEntityID($entity) {
+    $extract_ids = entity_extract_IDs($this->remote['entity_type'], $entity);
+    return array_shift($extract_ids);
+  }
+
+  /**
+   * Gets all the entities referenced by the local entity.
+   *
+   * @return array
+   *  Array of fully loaded referenced entities keyed by ID, or empty
+   *  array if nothing has been referenced.
+   */
+  protected function getReferencedEntities() {
+    $IDs = $this->getLocalReferenceIDs();
+    return $IDs ? entity_load($this->remote['entity_type'], $IDs) : array();
+  }
+
+  /**
+   * Gets the IDs of the entities referenced by the local entity.
+   *
+   * @return array
+   *  Array of entity IDs, empty array if there are no references.
+   */
+  protected function getLocalReferenceIDs() {
+    return $this->getReferenceIDs($this->entity, $this->local);
+  }
+
+  /**
+   * Gets the IDs of the entities referenced by $entity.
+   *
+   * @param object $entity
+   *  The remote entity.
+   *
+   * @return array
+   *  Array of entity IDs, empty array if there are no references.
+   */
+  protected function getRemoteReferenceIDs($entity) {
+    return $this->getReferenceIDs($entity, $this->remote);
+  }
+
+  /**
+   * Check if a field can support any more values. Formerly known as
+   * "reference overloading".
+   *
+   * @param array $references
+   *  The values in the field.
+   *
+   * @param $field
+   *  Field definition (i.e., from field_info_field).
+   *
+   * @return boolean
+   */
+  private function filled($references, $field) {
+    return $field['cardinality'] != FIELD_CARDINALITY_UNLIMITED && sizeof($references) >= $field['cardinality'];
+  }
+
+  /**
+   * Gets all the referenced entity IDs from a specific field on $entity.
+   *
+   * @param object $entity
+   *  The entity to scan for references.
+   *
+   * @param array $field
+   *  Field or instance definition.
+   *
+   * @return array
+   *  Array of unique IDs, empty if there are no references or the field
+   *  does not exist on $entity.
+   */
+  private function getReferenceIDs($entity, $field) {
+    $IDs = array();
+    if (isset($entity->{$field['field_name']})) {
+      foreach ($entity->{$field['field_name']} as $references) {
+        foreach ($references as $reference) {
+          $IDs[] = $reference['target_id'];
+        }
+      }
+    }
+    return array_unique(array_filter($IDs));
+  }
+
+}

sites/all/modules/contrib/fields/cer/tests/cer_tests.info

@@ -0,0 +1,16 @@
+name = "CER Tests"
+core = "7.x"
+description = "Automated tests for CER."
+hidden = TRUE
+
+dependencies[] = simpletest
+dependencies[] = cer
+
+files[] = crud.test
+files[] = fields.test
+; Information added by drupal.org packaging script on 2013-05-01
+version = "7.x-2.x-dev"
+core = "7.x"
+project = "cer"
+datestamp = "1367412087"
+

sites/all/modules/contrib/fields/cer/tests/cer_tests.module

@@ -0,0 +1 @@
+<?php

sites/all/modules/contrib/fields/cer/tests/crud.test

@@ -0,0 +1,168 @@
+<?php
+
+class CerCrudTest extends DrupalWebTestCase {
+
+  public static function getInfo() {
+    return array(
+      'name' => 'CRUD',
+      'group' => 'Corresponding Entity Reference',
+      'description' => 'Tests basic CER functionality.',
+    );
+  }
+
+  public function setUp() {
+    parent::setUp('field', 'field_sql_storage', 'ctools', 'entityreference', 'cer');
+
+    field_create_field(array(
+      'field_name' => 'field_user',
+      'type' => 'entityreference',
+      'cardinality' => -1,
+      'settings' => array(
+        'target_type' => 'user',
+      ),
+    ));
+    field_create_field(array(
+      'field_name' => 'field_node',
+      'type' => 'entityreference',
+      'cardinality' => -1,
+      'settings' => array(
+        'target_type' => 'node',
+      ),
+    ));
+
+    field_create_instance(array(
+      'field_name' => 'field_user',
+      'entity_type' => 'node',
+      'bundle' => 'page',
+    ));
+    field_create_instance(array(
+      'field_name' => 'field_node',
+      'entity_type' => 'user',
+      'bundle' => 'user',
+    ));
+
+    db_insert('cer')->fields(array(
+      'entity_types_content_fields' => 'node*page*field_user*user*user*field_node',
+      'enabled' => TRUE,
+    ))->execute();
+  }
+
+  public function testImplicitReferenceCreation() {
+    $uid = $this->drupalCreateUser()->uid;
+    
+    $referrers = array();
+    for ($i = 0; $i < 5; $i++) {
+      $referrers[] = $this->drupalCreateNode(array(
+        'type' => 'page',
+        'field_user' => array(
+          'und' => array(
+            array('target_id' => $uid),
+          ),
+        ),
+      ))->nid;
+    }
+
+    $references = array();
+    foreach (user_load($uid, TRUE)->field_node['und'] as $reference) {
+      $references[] = $reference['target_id'];
+    }
+    $this->assertFalse(array_diff($referrers, $references), 'Creating 5 referrers to a single entity creates 5 corresponding references on that entity.', 'CER');
+  }
+
+  public function testDuplicateReferencePrevention() {
+    $uid = $this->drupalCreateUser()->uid;
+
+    $this->drupalCreateNode(array(
+      'type' => 'page',
+      'field_user' => array(
+        'und' => array(
+          array('target_id' => $uid),
+          array('target_id' => $uid),
+        ),
+      ),
+    ));
+
+    $account = user_load($uid, TRUE);
+    $this->assertEqual(sizeof($account->field_node['und']), 1, 'Creating two references to an entity from a single referrer creates one corresponding reference.', 'CER');
+  }
+
+  public function testExplicitReferenceCreation() {
+    $uid = $this->drupalCreateNode()->uid;
+
+    $node = $this->drupalCreateNode(array('type' => 'page'));
+    $node->field_user['und'][0]['target_id'] = $uid;
+    node_save($node);
+
+    $account = user_load($uid, TRUE);
+    $this->assertEqual($account->field_node['und'][0]['target_id'], $node->nid, 'Creating an explicit reference between to unrelated entities creates a corresponding reference.', 'CER');
+  }
+
+  public function testExplicitDereference() {
+    $uid = $this->drupalCreateUser()->uid;
+
+    $nid = $this->drupalCreateNode(array(
+      'type' => 'page',
+      'field_user' => array(
+        'und' => array(
+          array('target_id' => $uid),
+        ),
+      ),
+    ))->nid;
+
+    $account = user_load($uid, TRUE);
+    $account->field_node = array();
+    user_save($account);
+
+    $node = node_load($nid, NULL, TRUE);
+    $this->assertFalse($node->field_user, 'Explicitly clearing a reference from the referenced entity clears the corresponding reference on the referrer.', 'CER');
+  }
+
+  public function testReferrerDeletion() {
+    $uid = $this->drupalCreateUser()->uid;
+    
+    $referrers = array();
+    for ($i = 0; $i < 5; $i++) {
+      $referrers[] = $this->drupalCreateNode(array(
+        'type' => 'page',
+        'field_user' => array(
+          'und' => array(
+            array('target_id' => $uid),
+          ),
+        ),
+      ))->nid;
+    }
+
+    node_delete($referrers[0]);
+
+    $references = array();
+    foreach (user_load($uid, TRUE)->field_node['und'] as $reference) {
+      $references[] = $reference['target_id'];
+    }
+    $this->assertFalse(in_array($referrers[0], $references), 'Deleting a referrer clears corresponding reference on the referenced entity.', 'CER');
+  }
+
+  public function testReferencedEntityDeletion() {
+    $uid = $this->drupalCreateUser()->uid;
+
+    $referrers = array();
+    for ($i = 0; $i < 5; $i++) {
+      $referrers[] = $this->drupalCreateNode(array(
+        'type' => 'page',
+        'field_user' => array(
+          'und' => array(
+            array('target_id' => $uid),
+          ),
+        ),
+      ))->nid;
+    }
+    user_delete($uid);
+
+    $cleared = 0;
+    foreach ($referrers as $nid) {
+      $node = node_load($nid, NULL, TRUE);
+      $cleared += (int) empty($node->field_user);
+    }
+    $this->assertEqual($cleared, sizeof($referrers), 'Deleting a referenced entity clears all references to it.', 'CER');
+  }
+
+}

sites/all/modules/contrib/fields/cer/tests/fields.test

@@ -0,0 +1,67 @@
+<?php
+
+class CerFieldTestCase extends DrupalWebTestCase {
+
+  public static function getInfo() {
+    return array(
+      'name' => 'Fields',
+      'group' => 'Corresponding Entity Reference',
+      'description' => 'Tests integration with the Field API.',
+    );
+  }
+
+  public function setUp() {
+    parent::setUp('field', 'field_sql_storage', 'ctools', 'entityreference', 'cer');
+
+    field_create_field(array(
+      'field_name' => 'field_user',
+      'type' => 'entityreference',
+      'cardinality' => -1,
+      'settings' => array(
+        'target_type' => 'user',
+      ),
+    ));
+    field_create_field(array(
+      'field_name' => 'field_node',
+      'type' => 'entityreference',
+      'cardinality' => -1,
+      'settings' => array(
+        'target_type' => 'node',
+      ),
+    ));
+
+    field_create_instance(array(
+      'field_name' => 'field_user',
+      'entity_type' => 'node',
+      'bundle' => 'page',
+    ));
+    field_create_instance(array(
+      'field_name' => 'field_node',
+      'entity_type' => 'user',
+      'bundle' => 'user',
+    ));
+    
+    ctools_include('export');
+
+    $preset = ctools_export_crud_new('cer');
+    $preset->entity_types_content_fields = 'node*page*field_user*user*user*field_node';
+    $preset->enabled = TRUE;
+
+    ctools_export_crud_save('cer', $preset);
+  }
+
+  public function testFieldInstanceDelete() {
+    field_delete_instance(field_info_instance('user', 'field_node', 'user'));
+
+    $preset = cer_preset_load('node*page*field_user*user*user*field_node');
+    $this->assertNull($preset, 'Deleting a field instance clears CER presets for that instance.');
+  }
+
+  public function testFieldDelete() {
+    field_delete_field('field_user');
+
+    $preset = cer_preset_load('node*page*field_user*user*user*field_node');
+    $this->assertNull($preset, 'Deleting a field clears CER presets for that field.');
+  }
+
+}