Index: inline_entity_form.module
===================================================================
--- inline_entity_form.module	(revision 323)
+++ inline_entity_form.module	(working copy)
@@ -76,6 +76,7 @@
     'settings' => array(
       'fields' => array(),
       'type_settings' => array(),
+			'match_operator' => 'CONTAINS',
     ),
     'behaviors' => array(
       'multiple values' => FIELD_BEHAVIOR_CUSTOM,
@@ -116,6 +117,16 @@
     );
     $element['type_settings'] += $settings_form;
   }
+  $element['match_operator'] = array(
+    '#type' => 'select',
+    '#title' => t('Autocomplete matching'),
+    '#default_value' => $settings['match_operator'],
+    '#options' => array(
+      'STARTS_WITH' => t('Starts with'),
+      'CONTAINS' => t('Contains'),
+    ),
+    '#description' => t('Select the method used to collect autocomplete suggestions. Note that <em>Contains</em> can cause performance issues on sites with thousands of nodes.'),
+  );
 
   return $element;
 }
@@ -128,12 +139,14 @@
  *   - entity_type - The entity_type being managed.
  *   - bundles - Bundles of entities that the user is allowed to create.
  *   - column - The name of the ref. field column that stores the entity id.
+ *   - field_type - The type of the field being edited.
  */
 function inline_entity_form_settings($field, $instance) {
   $settings = array(
     'entity_type' => NULL,
     'bundles' => array(),
     'column' => NULL,
+    'field_type' => $field['type'],
   );
 
   if ($field['type'] == 'commerce_product_reference') {
@@ -251,17 +264,7 @@
 
       $delta++;
     }
-
-    // If no entities were found, try to open the add form.
-    if (empty($form_state['inline_entity_form'][$ief_id]['entities'])) {
-      if (count($settings['bundles']) == 1 && $instance['required']) {
-        $form_state['inline_entity_form'][$ief_id]['form'] = 'add';
-        $form_state['inline_entity_form'][$ief_id]['form settings'] = array(
-          'bundle' => reset($settings['bundles']),
-        );
       }
-    }
-  }
 
   // If the reference field must always have one entity of a specific type,
   // provide a simplified widget that shows the entity form inline, without any
@@ -429,6 +432,20 @@
         '#submit' => array('inline_entity_form_open_form'),
         '#ief_form' => 'add',
       );
+
+      $element['actions']['ief_attach'] = array(
+        '#type' => 'submit',
+        '#value' => t('Attach an existing @type_singular', array('@type_singular' => $labels['singular'])),
+        '#name' => 'ief-' . $ief_id . '-attach',
+        '#limit_validation_errors' => array(array_merge($parents, array('actions'))),
+        '#ajax' => array(
+          'callback' => 'inline_entity_form_get_element',
+          'wrapper' => $wrapper,
+        ),
+        '#submit' => array('inline_entity_form_open_form'),
+        '#ief_form' => 'attach',
+      );
+
     }
     else {
       // There's a form open, show it.
@@ -454,6 +471,10 @@
           $element['form']['actions']['ief_add_cancel']['#access'] = FALSE;
         }
       }
+      elseif ($form_state['inline_entity_form'][$ief_id]['form'] == 'attach') {
+        $element['form']['#op'] = 'attach';
+        $element['form'] += inline_entity_form_attach_entity_form($controller,$element['form'], $form_state);
+      }
 
       // No entities have been added. Remove the outer fieldset to reduce
       // visual noise caused by having two titles.
@@ -611,6 +632,149 @@
 }
 
 /**
+ * Provides the entity attach form for attaching existing entities
+ *
+ * @param $entity_form
+ *   The form array that will receive the entity form.
+ * @param $form_state
+ *   The form state of the parent form.
+ *
+ * @return
+ *   The form array containing the embedded entity form.
+ */
+function inline_entity_form_attach_entity_form($controller, $entity_form, &$form_state) {
+  $labels = $controller->labels();
+  $bundle = $form_state['inline_entity_form'][$entity_form['#ief_id']]['form settings']['bundle'];
+
+  $entity_form['existing_entity'] = array(
+    '#type' => 'textfield',
+    '#title' => t('@label', array('@label' => ucwords($labels['singular']))),
+    '#description' => t('Enter the @label to be referenced', array('@label' => $labels['singular'])),
+    '#required' => TRUE,
+  );
+
+  // Add the appropriate autocomplete path to the widget.
+  $settings = $form_state['inline_entity_form'][$entity_form['#ief_id']]['settings'];
+  switch ($settings['field_type']) {
+    case 'entityreference':
+      // Get the entity variables of the complete form to create the path for
+      // Entity reference's autocomplete.
+      $parents = $entity_form['#parents'];
+      array_pop($parents);
+      $element = drupal_array_get_nested_value($form_state['complete form'], $parents);
+      list($form_entity_id, ,) = entity_extract_ids($element['#entity_type'], $element['#entity']);
+      $autocomplete_path = 'entityreference/autocomplete/single';
+      $autocomplete_path .= '/' . $element['#field_name'] . '/' . $element['#entity_type'] . '/' . $element['#bundle'] . '/' . $form_entity_id;
+
+      $entity_form['existing_entity']['#autocomplete_path'] = $autocomplete_path;
+      // Entity reference autocomplete requires its validate handler to
+      // convert the values to the correct autocomplete path.
+      $entity_form['existing_entity']['#element_validate'] = array('_entityreference_autocomplete_validate');
+      break;
+    case 'commerce_product_reference':
+      $entity_form['existing_entity']['#autocomplete_path'] = 'commerce_product/autocomplete/commerce_product/commerce_product/' . $bundle;
+      break;
+  }
+   // Add the actions
+  $entity_form['actions'] = array(
+    '#type' => 'container',
+    '#weight' => 100,
+  );
+  $entity_form['actions']['ief_' . $entity_form['#op'] . '_save'] = array(
+    '#type' => 'submit',
+    '#value' => t('Attach @type_singular', array('@type_singular' => $labels['singular'])),
+    '#name' => 'ief-' . $entity_form['#op'] . '-submit-' . $entity_form['#ief_id'],
+    '#limit_validation_errors' => array($entity_form['#parents']),
+    '#attributes' => array('class' => array('ief-entity-submit')),
+    '#ajax' => array(
+      'callback' => 'inline_entity_form_get_element',
+      'wrapper' => 'inline-entity-form-' . $entity_form['#ief_id'],
+    ),
+  );
+  $entity_form['actions']['ief_' . $entity_form['#op'] . '_cancel'] = array(
+    '#type' => 'submit',
+    '#value' => t('Cancel'),
+    '#name' => 'ief-' . $entity_form['#op'] . '-cancel-' . $entity_form['#ief_id'],
+    '#limit_validation_errors' => array(),
+    '#ajax' => array(
+      'callback' => 'inline_entity_form_get_element',
+      'wrapper' => 'inline-entity-form-' . $entity_form['#ief_id'],
+    ),
+  );
+  // Add the appropriate submit handlers and their related data.
+  $entity_form['actions']['ief_' . $entity_form['#op'] . '_save']['#submit'] = array('inline_entity_form_close_form');
+  $entity_form['actions']['ief_' . $entity_form['#op'] . '_cancel']['#submit'] = array('inline_entity_form_close_form');
+  $entity_form['#element_validate'][] = 'inline_entity_form_process_attach_entity_form';
+  return $entity_form;
+}
+
+/**
+ * Processes an entity attach form submission.
+ *
+ * The entity attach form loads the entity using the subitted entity id/sku
+ * If the entity is loaded successfully, existing entities in the IEF array are
+ * compared to prevent duplicates. If all validation passes the entity is
+ * attached to the entities array and the IEF table is updated.
+ *
+ * @param $entity_form
+ *  The form of the entity being managed inline.
+ * @param $form_state
+ *   The form state of the parent form.
+ */
+function inline_entity_form_process_attach_entity_form(&$entity_form, &$form_state) {
+  $ief_id = $entity_form['#ief_id'];
+  $entity_type = $entity_form['#entity_type'];
+  $parents_path = implode('][', $entity_form['#parents']);
+
+  $form_values = drupal_array_get_nested_value($form_state['values'], $entity_form['#parents']);
+  $existing_entity = $form_values['existing_entity'];
+
+  // Instantiate controller to access labels
+  $entity_info = entity_get_info($entity_type);
+  $type_settings = $form_state['inline_entity_form'][$ief_id]['type_settings'];
+  $controller = new $entity_info['inline entity form']['controller']($entity_type, $type_settings);
+  $labels = $controller->labels();
+
+  // The value we get from the autocomplete depends on the field type we're on.
+  $settings = $form_state['inline_entity_form'][$ief_id]['settings'];
+  switch ($settings['field_type']) {
+    case 'entityreference':
+      // $existing_entity is an entity ID.
+      $load_entity = entity_load($entity_form['#entity_type'], array($existing_entity));
+      $attach_entity = $load_entity[$existing_entity];
+      break;
+    case 'commerce_product_reference':
+      // Load commerce_product entity by SKU
+      $attach_entity = commerce_product_load_by_sku($existing_entity);
+      break;
+  }
+
+  // Check to see if entity is already referenced by current IEF widget
+  if (!empty($attach_entity)) {
+    foreach ($form_state['inline_entity_form'][$ief_id]['entities'] as $key => $entity) {
+      if ($entity['entity'] == $attach_entity) {
+        form_set_error($parents_path . '][existing_entity', t('This selected @label has already been referenced', array('@label' => $labels['singular'])));
+        unset($attach_entity);
+      }
+    }
+  }
+  else {
+    form_set_error($parents_path . '][existing_entity', t('This selected @label is not valid.', array('@label' => $labels['singular'])));
+  }
+
+  // If validation passes attach entity to the entities array
+  if (!empty($attach_entity)) {
+    $form_state['inline_entity_form'][$ief_id]['entities'][] = array(
+      'entity' => $attach_entity,
+      'weight' => $key + 1,
+      'form' => NULL,
+      'needs_save' => FALSE,
+    );
+  }
+}
+
+
+/**
  * Wraps and returns the delete form provided by the passed-in controller.
  *
  * @param $controller